Tag Archives: BGP

DMVPN Phase 3

March 2, 2017Cisco, DMVPN, VPNBGP, DMVPN, EIGRP, IPSec VPN, mGRE, NHRP, NHRP Shortcut Switching, OSPF, Phase 3, Route-reflector, VPNAmolak

DMVPN Phase 3

The Shortcut Switching Enhancements for NHRP in DMVPN Phase 3 provides a more scalable alternative to the previous NHRP model. Routers in a Dynamic Multipoint VPN (DMVPN) Phase 3 network use Next Hop Resolution Protocol (NHRP) Shortcut Switching to discover shorter paths to a destination network after receiving an NHRP redirect message from the hub. This allows the routers to communicate directly with each other without the need for an intermediate hop.

Benefits of DMVPN Phase 3 Design:

Allows summarization of routing protocol updates from hub to spokes. The spokes no longer need to have an individual route with an IP next-hop of the tunnel IP address of the remote spoke for the networks behind all the other spokes. The spokes can use summarized routes or specific routes with an IP next-hop of the tunnel IP address of the hub and still be able to build spoke-to-spoke tunnels.
Allows for hierarchical (greater than one level) and more complex tree-based DMVPN network topologies. Tree-based topologies allow the capability to build DMVPN networks with regional hubs that are spokes of central hubs. This architecture
allows the regional hub to handle the data and NHRP control traffic for its regional spokes, but still allows spoke-to-spoke tunnels to be built between any spokes within the DMVPN network, whether they are in the same region or not. This architecture also allows the DMVPN network layout to more closely match regional or hierarchical data flow patterns.

Check these links for

DMVPN basics – http://www.amolak.net/dmvpn-basics/
DMVPN Phase 1 Configuration – http://www.amolak.net/dmvpn-phase-1/
DMVPN Phase 2 Configuration – http://www.amolak.net/dmvpn-phase-2/

Here is the network topology for DMVPN phase 3 discussion and configuration.

The DMVPN Phase 2 design requires to maintain full routing table on all spoke routers. Each route for remote spoke networks needs to be a specific route with the next hop pointing to the remote spoke’s tunnel address. This prevents the hub from being able to send down a summarized route to the spokes for a more concise routing table.

Phase 3 overcomes this restriction using NHRP traffic indication messages from the hub to signal to the spokes that a better path exists to reach the target network. This functionality is enabled by configuring ip nhrp redirect on the hub and ip nhrp shortcut on the spokes. The redirect command tells the hub to send the NHRP traffic indication message while the shortcut command tells the spokes to accept the redirect and install the shortcut route.

DMVPN Phase 3 configuration with EIGRP

Configuration:

----------
R1 - Hub:
----------

hostname R1
!
ip cef
!
crypto isakmp policy 10
 encr aes
 authentication pre-share
 group 2
crypto isakmp key DmVpNpR3$h@r3dK3Y address 0.0.0.0        
!
!
crypto ipsec transform-set TRANSFORM-SET esp-aes esp-sha-hmac 
 mode transport
!
crypto ipsec profile PROTECT-GRE
 set transform-set TRANSFORM-SET 
!
interface Tunnel0
 bandwidth 4096
 ip address 192.168.1.1 255.255.255.0
 no ip redirects
 ip mtu 1400
 ip nhrp authentication NhRp@UtH
 ip nhrp map multicast dynamic
 ip nhrp network-id 100
 ip nhrp redirect
 ip summary-address eigrp 100 10.10.0.0 255.255.0.0
 ip tcp adjust-mss 1360
 tunnel source FastEthernet0/0
 tunnel mode gre multipoint
 tunnel key 123
 tunnel protection ipsec profile PROTECT-GRE
!
interface FastEthernet0/0
 ip address 1.1.14.1 255.255.255.0
!
interface FastEthernet0/1
 ip address 10.10.1.1 255.255.255.0
!
router eigrp 100
 network 10.10.1.1 0.0.0.0
 network 192.168.1.1 0.0.0.0
!
ip route 0.0.0.0 0.0.0.0 1.1.14.4

------------
R2 - Spoke:
------------

hostname R2
!
ip cef
!
crypto isakmp policy 10
 encr aes
 authentication pre-share
 group 2
crypto isakmp key DmVpNpR3$h@r3dK3Y address 0.0.0.0        
!
!
crypto ipsec transform-set TRANSFORM-SET esp-aes esp-sha-hmac 
 mode transport
!
crypto ipsec profile PROTECT-GRE
 set transform-set TRANSFORM-SET 
!
interface Tunnel0
 bandwidth 4096
 ip address 192.168.1.2 255.255.255.0
 no ip redirects
 ip mtu 1400
 ip nhrp authentication NhRp@UtH
 ip nhrp map multicast 1.1.14.1
 ip nhrp map 192.168.1.1 1.1.14.1
 ip nhrp network-id 100
 ip nhrp nhs 192.168.1.1
 ip nhrp shortcut
 ip tcp adjust-mss 1360
 tunnel source FastEthernet0/0
 tunnel mode gre multipoint
 tunnel key 123
 tunnel protection ipsec profile PROTECT-GRE
!
interface FastEthernet0/0
 ip address 1.1.24.2 255.255.255.0
!
interface FastEthernet0/1
 ip address 10.10.2.2 255.255.255.0
!
router eigrp 100
 network 10.10.2.2 0.0.0.0
 network 192.168.1.2 0.0.0.0
!
ip route 0.0.0.0 0.0.0.0 1.1.24.4

------------
R3 - Spoke:
------------

hostname R3
!
ip cef
!
crypto isakmp policy 10
 encr aes
 authentication pre-share
 group 2
crypto isakmp key DmVpNpR3$h@r3dK3Y address 0.0.0.0        
!
!
crypto ipsec transform-set TRANSFORM-SET esp-aes esp-sha-hmac 
 mode transport
!
crypto ipsec profile PROTECT-GRE
 set transform-set TRANSFORM-SET 
!
interface Tunnel0
 bandwidth 4096
 ip address 192.168.1.3 255.255.255.0
 no ip redirects
 ip mtu 1400
 ip nhrp authentication NhRp@UtH
 ip nhrp map multicast 1.1.14.1
 ip nhrp map 192.168.1.1 1.1.14.1
 ip nhrp network-id 100
 ip nhrp nhs 192.168.1.1
 ip nhrp shortcut
 ip tcp adjust-mss 1360
 tunnel source FastEthernet0/0
 tunnel mode gre multipoint
 tunnel key 123
 tunnel protection ipsec profile PROTECT-GRE
!
interface FastEthernet0/0
 ip address 1.1.34.3 255.255.255.0
!
interface FastEthernet0/1
 ip address 10.10.3.3 255.255.255.0
!
router eigrp 100
 network 10.10.3.3 0.0.0.0
 network 192.168.1.3 0.0.0.0
!
ip route 0.0.0.0 0.0.0.0 1.1.34.4

---------------
R4 - Internet:
---------------

hostname R4
!
interface FastEthernet0/0
 ip address 1.1.14.4 255.255.255.0
!
interface FastEthernet0/1
 ip address 1.1.24.4 255.255.255.0
!
interface FastEthernet1/0
 ip address 1.1.34.4 255.255.255.0
!

Verification:

- Hub and Spokes routers are using mGRE tunnels

R1#show int t0
Tunnel0 is up, line protocol is up 
  Hardware is Tunnel
  Internet address is 192.168.1.1/24
  MTU 17870 bytes, BW 4096 Kbit/sec, DLY 50000 usec, 
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation TUNNEL, loopback not set
  Keepalive not set
  Tunnel source 1.1.14.1 (FastEthernet0/0)
   Tunnel Subblocks:
      src-track:
         Tunnel0 source tracking subblock associated with FastEthernet0/0
          Set of tunnels with source FastEthernet0/0, 1 member (includes iterators), on interface <OK>
  Tunnel protocol/transport multi-GRE/IP

R2#show int t0
Tunnel0 is up, line protocol is up 
  Hardware is Tunnel
  Internet address is 192.168.1.2/24
  MTU 17870 bytes, BW 4096 Kbit/sec, DLY 50000 usec, 
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation TUNNEL, loopback not set
  Keepalive not set
  Tunnel source 1.1.24.2 (FastEthernet0/0)
   Tunnel Subblocks:
      src-track:
         Tunnel0 source tracking subblock associated with FastEthernet0/0
          Set of tunnels with source FastEthernet0/0, 1 member (includes iterators), on interface <OK>
  Tunnel protocol/transport multi-GRE/IP

R3#show int t0
Tunnel0 is up, line protocol is up 
  Hardware is Tunnel
  Internet address is 192.168.1.3/24
  MTU 17870 bytes, BW 4096 Kbit/sec, DLY 50000 usec, 
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation TUNNEL, loopback not set
  Keepalive not set
  Tunnel source 1.1.34.3 (FastEthernet0/0)
   Tunnel Subblocks:
      src-track:
         Tunnel0 source tracking subblock associated with FastEthernet0/0
          Set of tunnels with source FastEthernet0/0, 1 member (includes iterators), on interface <OK>
  Tunnel protocol/transport multi-GRE/IP

- Routing adjacencies (EIGRP neighborship) are between Hub and Spokes only 

R1#show ip eigrp neighbors
EIGRP-IPv4 Neighbors for AS(100)
H   Address                 Interface              Hold Uptime   SRTT   RTO  Q  Seq
                                                   (sec)         (ms)       Cnt Num
1   192.168.1.2             Tu0                      10 00:28:43  188  1128  0  3
0   192.168.1.3             Tu0                      14 00:29:10  174  1044  0  3

R2#show ip eigrp neighbors
EIGRP-IPv4 Neighbors for AS(100)
H   Address                 Interface              Hold Uptime   SRTT   RTO  Q  Seq
                                                   (sec)         (ms)       Cnt Num
0   192.168.1.1             Tu0                      14 00:28:45 1282  5000  0  5

R3#show ip eigrp neighbors
EIGRP-IPv4 Neighbors for AS(100)
H   Address                 Interface              Hold Uptime   SRTT   RTO  Q  Seq
                                                   (sec)         (ms)       Cnt Num
0   192.168.1.1             Tu0                      11 00:29:16  200  1200  0  2

- Routing Table
- Hub router advertised a summary route (10.10.0.0/16) to spoke EIGRP routers


R1#show ip route eigrp | beg Gate
Gateway of last resort is 1.1.14.4 to network 0.0.0.0

      10.0.0.0/8 is variably subnetted, 5 subnets, 3 masks
D        10.10.0.0/16 is a summary, 00:30:13, Null0
D        10.10.2.0/24 [90/1907456] via 192.168.1.2, 00:29:34, Tunnel0
D        10.10.3.0/24 [90/1907456] via 192.168.1.3, 00:30:04, Tunnel0

R2#show ip route eigrp | beg Gate
Gateway of last resort is 1.1.24.4 to network 0.0.0.0

      10.0.0.0/8 is variably subnetted, 3 subnets, 3 masks
D        10.10.0.0/16 [90/1907456] via 192.168.1.1, 00:29:38, Tunnel0

R3#show ip route eigrp | beg Gate
Gateway of last resort is 1.1.34.4 to network 0.0.0.0

      10.0.0.0/8 is variably subnetted, 3 subnets, 3 masks
D        10.10.0.0/16 [90/1907456] via 192.168.1.1, 00:30:10, Tunnel0

- DMVPN Status
- Initially there is no spoke-to-spoke communication

R1#show dmvpn
Legend: Attrb --> S - Static, D - Dynamic, I - Incomplete
        N - NATed, L - Local, X - No Socket
        # Ent --> Number of NHRP entries with same NBMA peer
        NHS Status: E --> Expecting Replies, R --> Responding, W --> Waiting
        UpDn Time --> Up or Down Time for a Tunnel
====================================================================
Interface: Tunnel0, IPv4 NHRP Details 
Type:Hub, NHRP Peers:2, 

 # Ent  Peer NBMA Addr Peer Tunnel Add State  UpDn Tm Attrb
 ----- --------------- --------------- ----- -------- -----
     1 1.1.24.2            192.168.1.2    UP 00:30:53     D
     1 1.1.34.3            192.168.1.3    UP 00:31:22     D

R2#show dmvpn
Legend: Attrb --> S - Static, D - Dynamic, I - Incomplete
        N - NATed, L - Local, X - No Socket
        # Ent --> Number of NHRP entries with same NBMA peer
        NHS Status: E --> Expecting Replies, R --> Responding, W --> Waiting
        UpDn Time --> Up or Down Time for a Tunnel
======================================================================
Interface: Tunnel0, IPv4 NHRP Details 
Type:Spoke, NHRP Peers:1, 

 # Ent  Peer NBMA Addr Peer Tunnel Add State  UpDn Tm Attrb
 ----- --------------- --------------- ----- -------- -----
     1 1.1.14.1            192.168.1.1    UP 00:30:55     S

R3#show dmvpn
Legend: Attrb --> S - Static, D - Dynamic, I - Incomplete
        N - NATed, L - Local, X - No Socket
        # Ent --> Number of NHRP entries with same NBMA peer
        NHS Status: E --> Expecting Replies, R --> Responding, W --> Waiting
        UpDn Time --> Up or Down Time for a Tunnel
======================================================================
Interface: Tunnel0, IPv4 NHRP Details 
Type:Spoke, NHRP Peers:1, 

 # Ent  Peer NBMA Addr Peer Tunnel Add State  UpDn Tm Attrb
 ----- --------------- --------------- ----- -------- -----
     1 1.1.14.1            192.168.1.1    UP 00:31:26     S

- Traffic between Spoke R2 and Spoke R3
- First packet would traverse via Hub and it will trigger NHRP shortcut switching process then traffic will start using direct spoke-to-spoke tunnel

R2#trace 10.10.3.3 so 10.10.2.2
Type escape sequence to abort.
Tracing the route to 10.10.3.3
VRF info: (vrf in name/id, vrf out name/id)
  1 192.168.1.1 132 msec 136 msec 160 msec    << Hub R1 Tunnel IP  
  2 192.168.1.3 236 msec                      << Spoke R3 Tunnel IP

Following events occur for NHRP shortcut switching:

When the traffic between Spokes R2 & R3 arrives at Hub-R1 router, it will send redirect message (due to "ip nhrp redirect") to spokes to tell them, as both of you are DMVPN spokes and there would be a better path if you can build a direct spoke-to-spoke tunnel.

=> Hub-R1 sends NHRP redirect to Spoke-R2
R1#
*Mar  1 23:24:47.063: NHRP: Send Traffic Indication via Tunnel0 vrf 0, packet size: 100
*Mar  1 23:24:47.071:  src: 192.168.1.1, dst: 10.10.2.2
*Mar  1 23:24:47.079:  (F) afn: AF_IP(1), type: IP(800), hop: 255, ver: 1
*Mar  1 23:24:47.079:      shtl: 4(NSAP), sstl: 0(NSAP)
*Mar  1 23:24:47.083:      pktsz: 100 extoff: 68
*Mar  1 23:24:47.087:  (M) traffic code: redirect(0)
*Mar  1 23:24:47.087:      src NBMA: 1.1.14.1
*Mar  1 23:24:47.087:      src protocol: 192.168.1.1, dst protocol: 10.10.2.2
*Mar  1 23:24:47.087:      Contents of nhrp traffic indication packet:
*Mar  1 23:24:47.087:         45 00 00 64 00 00 00 00 FE 01 A3 80 0A 0A 02 02 
*Mar  1 23:24:47.087:         0A 0A 03 03 08 00 A8 A1 00 00 00 

=> Hub-R1 sends NHRP redirect to Spoke-R3
R1#
*Mar  1 23:24:47.139: NHRP: Send Traffic Indication via Tunnel0 vrf 0, packet size: 100
*Mar  1 23:24:47.143:  src: 192.168.1.1, dst: 10.10.3.3
*Mar  1 23:24:47.151:  (F) afn: AF_IP(1), type: IP(800), hop: 255, ver: 1
*Mar  1 23:24:47.155:      shtl: 4(NSAP), sstl: 0(NSAP)
*Mar  1 23:24:47.155:      pktsz: 100 extoff: 68
*Mar  1 23:24:47.159:  (M) traffic code: redirect(0)
*Mar  1 23:24:47.163:      src NBMA: 1.1.14.1
*Mar  1 23:24:47.163:      src protocol: 192.168.1.1, dst protocol: 10.10.3.3
*Mar  1 23:24:47.171:      Contents of nhrp traffic indication packet:
*Mar  1 23:24:47.175:         45 00 00 64 00 00 00 00 FE 01 A3 80 0A 0A 03 03 
*Mar  1 23:24:47.179:         0A 0A 02 02 00 00 B0 A1 00 00 00 

=> Spoke-R2 receives NHRP redirect from Hub-R1
R2#
*Mar  1 23:24:47.135: NHRP: Receive Traffic Indication via Tunnel0 vrf 0, packet size: 100
*Mar  1 23:24:47.139:  (F) afn: AF_IP(1), type: IP(800), hop: 255, ver: 1
*Mar  1 23:24:47.139:      shtl: 4(NSAP), sstl: 0(NSAP)
*Mar  1 23:24:47.139:      pktsz: 100 extoff: 68
*Mar  1 23:24:47.139:  (M) traffic code: redirect(0)
*Mar  1 23:24:47.139:      src NBMA: 1.1.14.1
*Mar  1 23:24:47.143:      src protocol: 192.168.1.1, dst protocol: 10.10.2.2
*Mar  1 23:24:47.143:      Contents of nhrp traffic indication packet:
*Mar  1 23:24:47.143:         45 00 00 64 00 00 00 00 FE 01 A3 80 0A 0A 02 02 
*Mar  1 23:24:47.143:         0A 0A 03 03 08 00 A8 A1 00 00 00 

=> Spoke-R2 will accept this message and want to build a shortcut path (direct spoke-to-spoke tunnel) because of "ip nhrp shortcut" command.
=> Spoke-R2 will send a NHRP resolution request to Spoke-R3 via Hub-R1, to find NBMA IP of Spoke-R3 to build a direct spoke-to-spoke tunnel   
 
R2#
*Mar  1 23:24:47.163: NHRP: Send Resolution Request via Tunnel0 vrf 0, packet size: 88
*Mar  1 23:24:47.167:  src: 192.168.1.2, dst: 10.10.3.3
*Mar  1 23:24:47.167:  (F) afn: AF_IP(1), type: IP(800), hop: 255, ver: 1
*Mar  1 23:24:47.167:      shtl: 4(NSAP), sstl: 0(NSAP)
*Mar  1 23:24:47.167:      pktsz: 88 extoff: 52
*Mar  1 23:24:47.167:  (M) flags: "router auth src-stable nat ", reqid: 2 
*Mar  1 23:24:47.167:      src NBMA: 1.1.24.2
*Mar  1 23:24:47.167:      src protocol: 192.168.1.2, dst protocol: 10.10.3.3
*Mar  1 23:24:47.167:  (C-1) code: no error(0)
*Mar  1 23:24:47.167:        prefix: 32, mtu: 17870, hd_time: 7200
*Mar  1 23:24:47.167:        addr_len: 0(NSAP), subaddr_len: 0(NSAP), proto_len: 0, pref: 0

=> Similar events happens on Spoke-R3.
=> Spoke-R3 receives NHRP redirect from Hub-R1
=> Spoke-R3 will also send a NHRP resolution request to Spoke-R2 via Hub-R1, to find NBMA IP of Spoke-R2 to build a direct spoke-to-spoke tunnel

R3#
*Mar  1 23:24:47.263: NHRP: Receive Traffic Indication via Tunnel0 vrf 0, packet size: 100
*Mar  1 23:24:47.267:  (F) afn: AF_IP(1), type: IP(800), hop: 255, ver: 1
*Mar  1 23:24:47.271:      shtl: 4(NSAP), sstl: 0(NSAP)
*Mar  1 23:24:47.275:      pktsz: 100 extoff: 68
*Mar  1 23:24:47.275:  (M) traffic code: redirect(0)
*Mar  1 23:24:47.275:      src NBMA: 1.1.14.1
*Mar  1 23:24:47.275:      src protocol: 192.168.1.1, dst protocol: 10.10.3.3
*Mar  1 23:24:47.275:      Contents of nhrp traffic indication packet:
*Mar  1 23:24:47.275:         45 00 00 64 00 00 00 00 FE 01 A3 80 0A 0A 03 03 
*Mar  1 23:24:47.275:         0A 0A 02 02 00 00 B0 A1 00 00 00 

R3#
*Mar  1 23:24:47.307: NHRP: Send Resolution Request via Tunnel0 vrf 0, packet size: 88
*Mar  1 23:24:47.311:  src: 192.168.1.3, dst: 10.10.2.2
*Mar  1 23:24:47.319:  (F) afn: AF_IP(1), type: IP(800), hop: 255, ver: 1
*Mar  1 23:24:47.323:      shtl: 4(NSAP), sstl: 0(NSAP)
*Mar  1 23:24:47.323:      pktsz: 88 extoff: 52

R3#*Mar  1 23:24:47.327:  (M) flags: "router auth src-stable nat ", reqid: 2 
*Mar  1 23:24:47.331:      src NBMA: 1.1.34.3
*Mar  1 23:24:47.335:      src protocol: 192.168.1.3, dst protocol: 10.10.2.2
*Mar  1 23:24:47.335:  (C-1) code: no error(0)
*Mar  1 23:24:47.335:        prefix: 32, mtu: 17870, hd_time: 7200
*Mar  1 23:24:47.335:        addr_len: 0(NSAP), subaddr_len: 0(NSAP), proto_len: 0, pref: 0

=> Hub-R1 receives NHRP resolution requests and forward it to both the spokes (R2 & R3)

R1#
*Mar  1 23:24:47.211: NHRP: Receive Resolution Request via Tunnel0 vrf 0, packet size: 88
*Mar  1 23:24:47.219:  (F) afn: AF_IP(1), type: IP(800), hop: 255, ver: 1
*Mar  1 23:24:47.219:      shtl: 4(NSAP), sstl: 0(NSAP)
*Mar  1 23:24:47.219:      pktsz: 88 extoff: 52
*Mar  1 23:24:47.219:  (M) flags: "router auth src-stable nat ", reqid: 2 
*Mar  1 23:24:47.219:      src NBMA: 1.1.24.2
*Mar  1 23:24:47.219:      src protocol: 192.168.1.2, dst protocol: 10.10.3.3
*Mar  1 23:24:47.219:  (C-1) code: no error(0)
*Mar  1 23:24:47.219:   
R1#     prefix: 32, mtu: 17870, hd_time: 7200
*Mar  1 23:24:47.219:        addr_len: 0(NSAP), subaddr_len: 0(NSAP), proto_len: 0, pref: 0
*Mar  1 23:24:47.223: NHRP: Forwarding Resolution Request via Tunnel0 vrf 0, packet size: 108
*Mar  1 23:24:47.223:  src: 192.168.1.1, dst: 10.10.3.3
*Mar  1 23:24:47.223:  (F) afn: AF_IP(1), type: IP(800), hop: 254, ver: 1
*Mar  1 23:24:47.223:      shtl: 4(NSAP), sstl: 0(NSAP)
*Mar  1 23:24:47.223:      pktsz: 108 extoff: 52
*Mar  1 23:24:47.223:  (M) flags: "router auth src-stable nat ", reqid: 2 
*Mar  1 23:24:47.223:      src NBMA: 1.1.24.2
*Mar  1 23:24:47.223:      src protocol: 192.168.1.2, dst protocol: 10.10.3.3
*Mar  1 23:24:47.223:  (C-1) code: no error(0)
*Mar  1 23:24:47.223:        prefix: 32, mtu: 17870, hd_time: 7200
*Mar  1 23:24:47.223:        addr_len: 0(NSAP), subaddr_len: 0(NSAP), proto_len: 0, pref: 0

R1#
*Mar  1 23:24:47.387: NHRP: Receive Resolution Request via Tunnel0 vrf 0, packet size: 88
*Mar  1 23:24:47.395:  (F)
R1# afn: AF_IP(1), type: IP(800), hop: 255, ver: 1
*Mar  1 23:24:47.399:      shtl: 4(NSAP), sstl: 0(NSAP)
*Mar  1 23:24:47.399:      pktsz: 88 extoff: 52
*Mar  1 23:24:47.403:  (M) flags: "router auth src-stable nat ", reqid: 2 
*Mar  1 23:24:47.403:      src NBMA: 1.1.34.3
*Mar  1 23:24:47.403:      src protocol: 192.168.1.3, dst protocol: 10.10.2.2
*Mar  1 23:24:47.403:  (C-1) code: no error(0)
*Mar  1 23:24:47.403:        prefix: 32, mtu: 17870, hd_time: 7200
*Mar  1 23:24:47.403:        addr_len: 0(NSAP), subaddr_len: 0(NSAP), proto_len: 0, pref: 0
*Mar  1 23:24:47.407: NHRP: Forwarding Resolution Request via Tunnel0 vrf 0, packet size: 108
*Mar  1 23:24:47.407:  src: 192.168.1.1, dst: 10.10.2.2
*Mar  1 23:24:47.407:  (F) afn: AF_IP(1), type: IP(800), hop: 254, ver: 1
*Mar  1 23:24:47.407:      shtl: 4(NSAP), sstl: 0(NSAP)
*Mar  1 23:24:47.407:      pktsz: 108 extoff: 52
*Mar  1 23:24:47.407:  (M) flags: "router auth src-stable nat ", reqid: 2 
*Mar  1 23:24:47.407:      src NBMA: 1.1.34.3
*Mar  1 23:24:47.407:      src protocol: 192.168.1.3, dst protocol: 10.10.2.2
*Mar  1 23:24:47.407:  (C-1) code: no error(0)
*Mar  1 23:24:47.407:        prefix: 32, mtu: 17870, hd_time: 7200
*Mar  1 23:24:47.407:        addr_len: 0(NSAP), subaddr_len: 0(NSAP), proto_len: 0, pref: 0

=> Both Spoke-R2 & Spoke-R3 send NHRP resolution reply via Hub-R1

R2#
*Mar  1 23:24:48.431: NHRP: Send Resolution Reply via Tunnel0 vrf 0, packet size: 136
*Mar  1 23:24:48.435:  src: 192.168.1.2, dst: 192.168.1.3

R3#
*Mar  1 23:24:48.267: NHRP: Send Resolution Reply via Tunnel0 vrf 0, packet size: 136
*Mar  1 23:24:48.271:  src: 192.168.1.3, dst: 192.168.1.2

=> Finally, both Spokes receives each other's NHRP resolution reply 

R2#
*Mar  1 23:24:48.311: NHRP: Receive Resolution Reply via Tunnel0 vrf 0, packet size: 136
*Mar  1 23:24:48.319:  (F) afn: AF_IP(1), type: IP(800), hop: 255, ver: 1
*Mar  1 23:24:48.323:      shtl: 4(NSAP), sstl: 0(NSAP)
*Mar  1 23:24:48.323:      pktsz: 136 extoff: 60
*Mar  1 23:24:48.327:  (M) flags: "router auth dst-stable unique src-stable nat ", reqid: 2 
*Mar  1 23:24:48.331:      src NBMA: 1.1.24.2
*Mar  1 23:24:48.335:      src protocol: 192.168.1.2, dst protocol: 10.10.3.3
*Mar  1 23:24:48.335:  (C-1) code: no error(0)
*Mar  1 23:24:48.335:        prefix: 24, mtu: 17870, hd_time: 7199
*Mar  1 23:24:48.335:        addr_len: 4(NSAP), subaddr_len: 0(NSAP), proto_len: 4, pref: 0
*Mar  1 23:24:48.335:        client NBMA: 1.1.34.3
*Mar  1 23:24:48.335:        client protocol: 192.168.1.3

R3#
*Mar  1 23:24:48.551: NHRP: Receive Resolution Reply via Tunnel0 vrf 0, packet size: 136
*Mar  1 23:24:48.559:  (F) afn: AF_IP(1), type: IP(800), hop: 255, ver: 1
*Mar  1 23:24:48.563:      shtl: 4(NSAP), sstl: 0(NSAP)
*Mar  1 23:24:48.563:      pktsz: 136 extoff: 60
*Mar  1 23:24:48.567:  (M) flags: "router auth dst-stable unique src-stable nat ", reqid: 2 
*Mar  1 23:24:48.571:      src NBMA: 1.1.34.3
*Mar  1 23:24:48.575:      src protocol: 192.168.1.3, dst protocol: 10.10.2.2
*Mar  1 23:24:48.579:  (C-1) code: no error(0)
*Mar  1 23:24:48.579:        prefix: 24, mtu: 17870, hd_time: 7200
*Mar  1 23:24:48.579:        addr_len: 4(NSAP), subaddr_len: 0(NSAP), proto_len: 4, pref: 0
*Mar  1 23:24:48.579:        client NBMA: 1.1.24.2
*Mar  1 23:24:48.579:        client protocol: 192.168.1.2

=> Now both spokes know each other's NBMA & Tunnel IP address, and can build a direct spoke-to-spoke tunnel
=> And both spokes add a NHRP shortcut route entry to reach each other's LAN subnet

R2#
*Mar  1 23:24:48.455: NHRP: Adding route entry for 10.10.3.0/24 to RIB
*Mar  1 23:24:48.455: NHRP: Route addition to RIB Successful 

R3#
*Mar  1 23:24:48.587: NHRP: Adding route entry for 10.10.2.0/24 to RIB
*Mar  1 23:24:48.595: NHRP: Route addition to RIB Successful 

- Let's test communication between Spoke-R2 and Spoke-R3 now

R2#ping 10.10.3.3 so 10.10.2.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.10.3.3, timeout is 2 seconds:
Packet sent with a source address of 10.10.2.2 
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 116/136/152 ms

- Now traffic between Spoke-R2 and Spoke-R3 is using direct DMVPN tunnel

R2#trace 10.10.3.3 so 10.10.2.2
Type escape sequence to abort.
Tracing the route to 10.10.3.3
VRF info: (vrf in name/id, vrf out name/id)
  1 192.168.1.3 148 msec *  116 msec        << Spoke-R3 Tunnel IP

- Spokes routing table would show a new NHRP routing entry to reach subnet behind other spoke router  

R2#show ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area 
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
       + - replicated route, % - next hop override

Gateway of last resort is 1.1.24.4 to network 0.0.0.0

S*    0.0.0.0/0 [1/0] via 1.1.24.4
      1.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        1.1.24.0/24 is directly connected, FastEthernet0/0
L        1.1.24.2/32 is directly connected, FastEthernet0/0
      10.0.0.0/8 is variably subnetted, 4 subnets, 3 masks
D        10.10.0.0/16 [90/1907456] via 192.168.1.1, 01:31:44, Tunnel0
C        10.10.2.0/24 is directly connected, FastEthernet0/1
L        10.10.2.2/32 is directly connected, FastEthernet0/1
H        10.10.3.0/24 [250/1] via 192.168.1.3, 00:05:13, Tunnel0
      192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks
C        192.168.1.0/24 is directly connected, Tunnel0
L        192.168.1.2/32 is directly connected, Tunnel0

R3#show ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area 
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
       + - replicated route, % - next hop override

Gateway of last resort is 1.1.34.4 to network 0.0.0.0

S*    0.0.0.0/0 [1/0] via 1.1.34.4
      1.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        1.1.34.0/24 is directly connected, FastEthernet0/0
L        1.1.34.3/32 is directly connected, FastEthernet0/0
      10.0.0.0/8 is variably subnetted, 4 subnets, 3 masks
D        10.10.0.0/16 [90/1907456] via 192.168.1.1, 01:32:12, Tunnel0
H        10.10.2.0/24 [250/1] via 192.168.1.2, 00:06:01, Tunnel0
C        10.10.3.0/24 is directly connected, FastEthernet0/1
L        10.10.3.3/32 is directly connected, FastEthernet0/1
      192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks
C        192.168.1.0/24 is directly connected, Tunnel0
L        192.168.1.3/32 is directly connected, Tunnel0

- DMVPN Status

R1#show dmvpn
Legend: Attrb --> S - Static, D - Dynamic, I - Incomplete
        N - NATed, L - Local, X - No Socket
        # Ent --> Number of NHRP entries with same NBMA peer
        NHS Status: E --> Expecting Replies, R --> Responding, W --> Waiting
        UpDn Time --> Up or Down Time for a Tunnel
======================================================================
Interface: Tunnel0, IPv4 NHRP Details 
Type:Hub, NHRP Peers:2, 

 # Ent  Peer NBMA Addr Peer Tunnel Add State  UpDn Tm Attrb
 ----- --------------- --------------- ----- -------- -----
     1 1.1.24.2            192.168.1.2    UP 01:37:55     D
     1 1.1.34.3            192.168.1.3    UP 01:37:36     D


R2#show dmvpn
Legend: Attrb --> S - Static, D - Dynamic, I - Incomplete
        N - NATed, L - Local, X - No Socket
        # Ent --> Number of NHRP entries with same NBMA peer
        NHS Status: E --> Expecting Replies, R --> Responding, W --> Waiting
        UpDn Time --> Up or Down Time for a Tunnel
======================================================================
Interface: Tunnel0, IPv4 NHRP Details 
Type:Spoke, NHRP Peers:2, 

 # Ent  Peer NBMA Addr Peer Tunnel Add State  UpDn Tm Attrb
 ----- --------------- --------------- ----- -------- -----
     2 1.1.34.3            192.168.1.3    UP 00:11:26   DT1
                           192.168.1.3    UP 00:11:26     D
     1 1.1.14.1            192.168.1.1    UP 01:37:59     S
*T1 - Route Installed

R3#show dmvpn
Legend: Attrb --> S - Static, D - Dynamic, I - Incomplete
        N - NATed, L - Local, X - No Socket
        # Ent --> Number of NHRP entries with same NBMA peer
        NHS Status: E --> Expecting Replies, R --> Responding, W --> Waiting
        UpDn Time --> Up or Down Time for a Tunnel
======================================================================
Interface: Tunnel0, IPv4 NHRP Details 
Type:Spoke, NHRP Peers:2, 

 # Ent  Peer NBMA Addr Peer Tunnel Add State  UpDn Tm Attrb
 ----- --------------- --------------- ----- -------- -----
     2 1.1.24.2            192.168.1.2    UP 00:11:29   DT1
                           192.168.1.2    UP 00:11:29     D
     1 1.1.14.1            192.168.1.1    UP 01:37:43     S
*T1 - Route Installed

- NHRP Table

R1#show ip nhrp
192.168.1.2/32 via 192.168.1.2
   Tunnel0 created 01:38:52, expire 01:41:01
   Type: dynamic, Flags: unique registered used 
   NBMA address: 1.1.24.2 
192.168.1.3/32 via 192.168.1.3
   Tunnel0 created 01:38:33, expire 01:41:00
   Type: dynamic, Flags: unique registered used 
   NBMA address: 1.1.34.3

R2#show ip nhrp
10.10.2.0/24 via 192.168.1.2
   Tunnel0 created 00:12:24, expire 01:47:35
   Type: dynamic, Flags: router unique local 
   NBMA address: 1.1.24.2 
    (no-socket) 
10.10.3.0/24 via 192.168.1.3
   Tunnel0 created 00:12:24, expire 01:47:35
   Type: dynamic, Flags: router used rib 
   NBMA address: 1.1.34.3 
192.168.1.1/32 via 192.168.1.1
   Tunnel0 created 01:39:13, never expire 
   Type: static, Flags: used 
   NBMA address: 1.1.14.1 
192.168.1.3/32 via 192.168.1.3
   Tunnel0 created 00:12:25, expire 01:47:35
   Type: dynamic, Flags: router implicit used 
   NBMA address: 1.1.34.3 

R3#show ip nhrp
10.10.2.0/24 via 192.168.1.2
   Tunnel0 created 00:12:26, expire 01:47:33
   Type: dynamic, Flags: router used rib 
   NBMA address: 1.1.24.2 
10.10.3.0/24 via 192.168.1.3
   Tunnel0 created 00:12:26, expire 01:47:33
   Type: dynamic, Flags: router unique local 
   NBMA address: 1.1.34.3 
    (no-socket) 
192.168.1.1/32 via 192.168.1.1
   Tunnel0 created 01:39:16, never expire 
   Type: static, Flags: used 
   NBMA address: 1.1.14.1 
192.168.1.2/32 via 192.168.1.2
   Tunnel0 created 00:12:27, expire 01:47:33
   Type: dynamic, Flags: router implicit used 
   NBMA address: 1.1.24.2

DMVPN Phase 3 configuration with OSPF

Tunnel mode mGRE on Hub and Spoke routers
OSPF network type would be point-to-multipoint on Hub and Spoke Routers
Route summarization is not feasible in single OSPF area, this is one of the main reason that OSPF is not an ideal routing protocol for DMVPN phase 3 designs
Shortcut route is marked with “%” symbol which indicates next-hop override feature. It means router is not using next-hop IP from OSPF RIB entry, instead it is using DMVPN tunnel IP of remote spoke to route traffic over direct DMVPN tunnel.

Configuration:

----------
R1 - Hub:
----------

hostname R1
!
ip cef
!
crypto isakmp policy 10
 encr aes
 authentication pre-share
 group 2
crypto isakmp key DmVpNpR3$h@r3dK3Y address 0.0.0.0        
!
!
crypto ipsec transform-set TRANSFORM-SET esp-aes esp-sha-hmac 
 mode transport
!
crypto ipsec profile PROTECT-GRE
 set transform-set TRANSFORM-SET 
!
interface Tunnel0
 bandwidth 4096
 ip address 192.168.1.1 255.255.255.0
 no ip redirects
 ip mtu 1400
 ip nhrp authentication NhRp@UtH
 ip nhrp map multicast dynamic
 ip nhrp network-id 100
 ip nhrp redirect
 ip tcp adjust-mss 1360
 ip ospf network point-to-multipoint
 tunnel source FastEthernet0/0
 tunnel mode gre multipoint
 tunnel key 123
 tunnel protection ipsec profile PROTECT-GRE
!
interface FastEthernet0/0
 ip address 1.1.14.1 255.255.255.0
!
interface FastEthernet0/1
 ip address 10.10.1.1 255.255.255.0
!
router ospf 1
 network 10.10.1.1 0.0.0.0 area 0
 network 192.168.1.1 0.0.0.0 area 0
!
ip route 0.0.0.0 0.0.0.0 1.1.14.4


------------
R2 - Spoke:
------------

hostname R2
!
ip cef
!
crypto isakmp policy 10
 encr aes
 authentication pre-share
 group 2
crypto isakmp key DmVpNpR3$h@r3dK3Y address 0.0.0.0        
!
!
crypto ipsec transform-set TRANSFORM-SET esp-aes esp-sha-hmac 
 mode transport
!
crypto ipsec profile PROTECT-GRE
 set transform-set TRANSFORM-SET 
!
interface Tunnel0
 bandwidth 4096
 ip address 192.168.1.2 255.255.255.0
 no ip redirects
 ip mtu 1400
 ip nhrp authentication NhRp@UtH
 ip nhrp map multicast 1.1.14.1
 ip nhrp map 192.168.1.1 1.1.14.1
 ip nhrp network-id 100
 ip nhrp nhs 192.168.1.1
 ip nhrp shortcut
 ip tcp adjust-mss 1360
 ip ospf network point-to-multipoint
 tunnel source FastEthernet0/0
 tunnel mode gre multipoint
 tunnel key 123
 tunnel protection ipsec profile PROTECT-GRE
!
interface FastEthernet0/0
 ip address 1.1.24.2 255.255.255.0
!
interface FastEthernet0/1
 ip address 10.10.2.2 255.255.255.0
!
router ospf 1
 network 10.10.2.2 0.0.0.0 area 0
 network 192.168.1.2 0.0.0.0 area 0
!
ip route 0.0.0.0 0.0.0.0 1.1.24.4

------------
R3 - Spoke:
------------

hostname R3
!
ip cef
!
crypto isakmp policy 10
 encr aes
 authentication pre-share
 group 2
crypto isakmp key DmVpNpR3$h@r3dK3Y address 0.0.0.0        
!
!
crypto ipsec transform-set TRANSFORM-SET esp-aes esp-sha-hmac 
 mode transport
!
crypto ipsec profile PROTECT-GRE
 set transform-set TRANSFORM-SET 
!
interface Tunnel0
 bandwidth 4096
 ip address 192.168.1.3 255.255.255.0
 no ip redirects
 ip mtu 1400
 ip nhrp authentication NhRp@UtH
 ip nhrp map multicast 1.1.14.1
 ip nhrp map 192.168.1.1 1.1.14.1
 ip nhrp network-id 100
 ip nhrp nhs 192.168.1.1
 ip nhrp shortcut
 ip tcp adjust-mss 1360
 ip ospf network point-to-multipoint
 tunnel source FastEthernet0/0
 tunnel mode gre multipoint
 tunnel key 123
 tunnel protection ipsec profile PROTECT-GRE
!
interface FastEthernet0/0
 ip address 1.1.34.3 255.255.255.0
!
interface FastEthernet0/1
 ip address 10.10.3.3 255.255.255.0
!
router ospf 1
 network 10.10.3.3 0.0.0.0 area 0
 network 192.168.1.3 0.0.0.0 area 0
!
ip route 0.0.0.0 0.0.0.0 1.1.34.4

Verification:

- Tunnel OSPF Network Type 

R1#show ip ospf int t0
Tunnel0 is up, line protocol is up 
  Internet Address 192.168.1.1/24, Area 0, Attached via Network Statement
  Process ID 1, Router ID 192.168.1.1, Network Type POINT_TO_MULTIPOINT, Cost: 24
  Topology-MTID    Cost    Disabled    Shutdown      Topology Name
        0           24        no          no            Base
  Transmit Delay is 1 sec, State POINT_TO_MULTIPOINT
  Timer intervals configured, Hello 30, Dead 120, Wait 120, Retransmit 5
    oob-resync timeout 120
    Hello due in 00:00:19
  Supports Link-local Signaling (LLS)
  Cisco NSF helper support enabled
  IETF NSF helper support enabled
  Index 2/2, flood queue length 0
  Next 0x0(0)/0x0(0)
  Last flood scan length is 1, maximum is 1
  Last flood scan time is 4 msec, maximum is 4 msec
  Neighbor Count is 2, Adjacent neighbor count is 2 
    Adjacent with neighbor 192.168.1.3
    Adjacent with neighbor 192.168.1.2
  Suppress hello for 0 neighbor(s)

R2#show ip ospf int t0
Tunnel0 is up, line protocol is up 
  Internet Address 192.168.1.2/24, Area 0, Attached via Network Statement
  Process ID 1, Router ID 192.168.1.2, Network Type POINT_TO_MULTIPOINT, Cost: 24
  Topology-MTID    Cost    Disabled    Shutdown      Topology Name
        0           24        no          no            Base
  Transmit Delay is 1 sec, State POINT_TO_MULTIPOINT
  Timer intervals configured, Hello 30, Dead 120, Wait 120, Retransmit 5
    oob-resync timeout 120
    Hello due in 00:00:15
  Supports Link-local Signaling (LLS)
  Cisco NSF helper support enabled
  IETF NSF helper support enabled
  Index 2/2, flood queue length 0
  Next 0x0(0)/0x0(0)
  Last flood scan length is 1, maximum is 1
  Last flood scan time is 0 msec, maximum is 4 msec
  Neighbor Count is 1, Adjacent neighbor count is 1 
    Adjacent with neighbor 192.168.1.1
  Suppress hello for 0 neighbor(s)

R3#show ip ospf int t0
Tunnel0 is up, line protocol is up 
  Internet Address 192.168.1.3/24, Area 0, Attached via Network Statement
  Process ID 1, Router ID 192.168.1.3, Network Type POINT_TO_MULTIPOINT, Cost: 24
  Topology-MTID    Cost    Disabled    Shutdown      Topology Name
        0           24        no          no            Base
  Transmit Delay is 1 sec, State POINT_TO_MULTIPOINT
  Timer intervals configured, Hello 30, Dead 120, Wait 120, Retransmit 5
    oob-resync timeout 120
    Hello due in 00:00:09
  Supports Link-local Signaling (LLS)
  Cisco NSF helper support enabled
  IETF NSF helper support enabled
  Index 2/2, flood queue length 0
  Next 0x0(0)/0x0(0)
  Last flood scan length is 1, maximum is 1
  Last flood scan time is 4 msec, maximum is 4 msec
  Neighbor Count is 1, Adjacent neighbor count is 1 
    Adjacent with neighbor 192.168.1.1
  Suppress hello for 0 neighbor(s)

- OSPF Adjacencies

R1#show ip ospf neighbor 

Neighbor ID     Pri   State           Dead Time   Address         Interface
192.168.1.3       0   FULL/  -        00:01:37    192.168.1.3     Tunnel0
192.168.1.2       0   FULL/  -        00:01:55    192.168.1.2     Tunnel0

R2#show ip ospf neighbor 

Neighbor ID     Pri   State           Dead Time   Address         Interface
192.168.1.1       0   FULL/  -        00:01:50    192.168.1.1     Tunnel0

R3#show ip ospf neighbor 

Neighbor ID     Pri   State           Dead Time   Address         Interface
192.168.1.1       0   FULL/  -        00:01:48    192.168.1.1     Tunnel0

- Traffic between Spoke-R2 and Spoke-R3 is via direct spoke-to-spoke DMVPN tunnel

R2#ping 10.10.3.3 so 10.10.2.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.10.3.3, timeout is 2 seconds:
Packet sent with a source address of 10.10.2.2 
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 120/134/148 ms

R2#trace 10.10.3.3 so 10.10.2.2
Type escape sequence to abort.
Tracing the route to 10.10.3.3
VRF info: (vrf in name/id, vrf out name/id)
  1 192.168.1.3 128 msec *  152 msec          << Spoke-R3 Tunnel IP

- DMVPN Status

R1#show dmvpn
Legend: Attrb --> S - Static, D - Dynamic, I - Incomplete
        N - NATed, L - Local, X - No Socket
        # Ent --> Number of NHRP entries with same NBMA peer
        NHS Status: E --> Expecting Replies, R --> Responding, W --> Waiting
        UpDn Time --> Up or Down Time for a Tunnel
======================================================================
Interface: Tunnel0, IPv4 NHRP Details 
Type:Hub, NHRP Peers:2, 

 # Ent  Peer NBMA Addr Peer Tunnel Add State  UpDn Tm Attrb
 ----- --------------- --------------- ----- -------- -----
     1 1.1.24.2            192.168.1.2    UP 01:33:58     D
     1 1.1.34.3            192.168.1.3    UP 01:33:48     D

R2#show dmvpn
Legend: Attrb --> S - Static, D - Dynamic, I - Incomplete
        N - NATed, L - Local, X - No Socket
        # Ent --> Number of NHRP entries with same NBMA peer
        NHS Status: E --> Expecting Replies, R --> Responding, W --> Waiting
        UpDn Time --> Up or Down Time for a Tunnel
======================================================================
Interface: Tunnel0, IPv4 NHRP Details 
Type:Spoke, NHRP Peers:2, 

 # Ent  Peer NBMA Addr Peer Tunnel Add State  UpDn Tm Attrb
 ----- --------------- --------------- ----- -------- -----
     2 1.1.34.3            192.168.1.3    UP 00:01:42   DT2
                           192.168.1.3    UP 00:01:42     D
     1 1.1.14.1            192.168.1.1    UP 01:34:01     S
*T2 - Nexthop-override

R3#show dmvpn
Legend: Attrb --> S - Static, D - Dynamic, I - Incomplete
        N - NATed, L - Local, X - No Socket
        # Ent --> Number of NHRP entries with same NBMA peer
        NHS Status: E --> Expecting Replies, R --> Responding, W --> Waiting
        UpDn Time --> Up or Down Time for a Tunnel
======================================================================
Interface: Tunnel0, IPv4 NHRP Details 
Type:Spoke, NHRP Peers:2, 

 # Ent  Peer NBMA Addr Peer Tunnel Add State  UpDn Tm Attrb
 ----- --------------- --------------- ----- -------- -----
     2 1.1.24.2            192.168.1.2    UP 00:01:44   DT2
                           192.168.1.2    UP 00:01:44     D
     1 1.1.14.1            192.168.1.1    UP 01:33:54     S
*T2 - Nexthop-override

- Routing Table

R1#show ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area 
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
       + - replicated route, % - next hop override

Gateway of last resort is 1.1.14.4 to network 0.0.0.0

S*    0.0.0.0/0 [1/0] via 1.1.14.4
      1.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        1.1.14.0/24 is directly connected, FastEthernet0/0
L        1.1.14.1/32 is directly connected, FastEthernet0/0
      10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
C        10.10.1.0/24 is directly connected, FastEthernet0/1
L        10.10.1.1/32 is directly connected, FastEthernet0/1
O        10.10.2.0/24 [110/25] via 192.168.1.2, 01:36:33, Tunnel0
O        10.10.3.0/24 [110/25] via 192.168.1.3, 01:36:03, Tunnel0
      192.168.1.0/24 is variably subnetted, 4 subnets, 2 masks
C        192.168.1.0/24 is directly connected, Tunnel0
L        192.168.1.1/32 is directly connected, Tunnel0
O        192.168.1.2/32 [110/24] via 192.168.1.2, 01:36:33, Tunnel0
O        192.168.1.3/32 [110/24] via 192.168.1.3, 01:36:03, Tunnel0

R2#show ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area 
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
       + - replicated route, % - next hop override

Gateway of last resort is 1.1.24.4 to network 0.0.0.0

S*    0.0.0.0/0 [1/0] via 1.1.24.4
      1.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        1.1.24.0/24 is directly connected, FastEthernet0/0
L        1.1.24.2/32 is directly connected, FastEthernet0/0
      10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
O        10.10.1.0/24 [110/25] via 192.168.1.1, 01:36:38, Tunnel0
C        10.10.2.0/24 is directly connected, FastEthernet0/1
L        10.10.2.2/32 is directly connected, FastEthernet0/1
O   %    10.10.3.0/24 [110/49] via 192.168.1.1, 01:35:58, Tunnel0
      192.168.1.0/24 is variably subnetted, 4 subnets, 2 masks
C        192.168.1.0/24 is directly connected, Tunnel0
O        192.168.1.1/32 [110/24] via 192.168.1.1, 01:36:38, Tunnel0
L        192.168.1.2/32 is directly connected, Tunnel0
O        192.168.1.3/32 [110/48] via 192.168.1.1, 01:35:58, Tunnel0

R3#show ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area 
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
       + - replicated route, % - next hop override

Gateway of last resort is 1.1.34.4 to network 0.0.0.0

S*    0.0.0.0/0 [1/0] via 1.1.34.4
      1.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        1.1.34.0/24 is directly connected, FastEthernet0/0
L        1.1.34.3/32 is directly connected, FastEthernet0/0
      10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
O        10.10.1.0/24 [110/25] via 192.168.1.1, 01:36:10, Tunnel0
O   %    10.10.2.0/24 [110/49] via 192.168.1.1, 01:36:10, Tunnel0
C        10.10.3.0/24 is directly connected, FastEthernet0/1
L        10.10.3.3/32 is directly connected, FastEthernet0/1
      192.168.1.0/24 is variably subnetted, 4 subnets, 2 masks
C        192.168.1.0/24 is directly connected, Tunnel0
O        192.168.1.1/32 [110/24] via 192.168.1.1, 01:36:10, Tunnel0
O        192.168.1.2/32 [110/48] via 192.168.1.1, 01:36:10, Tunnel0
L        192.168.1.3/32 is directly connected, Tunnel0

- NHRP Table

R1#show ip nhrp
192.168.1.2/32 via 192.168.1.2
   Tunnel0 created 01:45:40, expire 01:33:54
   Type: dynamic, Flags: unique registered used 
   NBMA address: 1.1.24.2 
192.168.1.3/32 via 192.168.1.3
   Tunnel0 created 01:45:30, expire 01:33:54
   Type: dynamic, Flags: unique registered used 
   NBMA address: 1.1.34.3 

R2#show ip nhrp
10.10.2.0/24 via 192.168.1.2
   Tunnel0 created 00:13:24, expire 01:46:35
   Type: dynamic, Flags: router unique local 
   NBMA address: 1.1.24.2 
    (no-socket) 
10.10.3.0/24 via 192.168.1.3
   Tunnel0 created 00:13:23, expire 01:46:36
   Type: dynamic, Flags: router used rib nho << next-hop override
   NBMA address: 1.1.34.3 
192.168.1.1/32 via 192.168.1.1
   Tunnel0 created 01:46:18, never expire 
   Type: static, Flags: used 
   NBMA address: 1.1.14.1 
192.168.1.3/32 via 192.168.1.3
   Tunnel0 created 00:13:24, expire 01:46:35
   Type: dynamic, Flags: router implicit 
   NBMA address: 1.1.34.3 

R3#show ip nhrp
10.10.2.0/24 via 192.168.1.2
   Tunnel0 created 00:13:30, expire 01:46:28
   Type: dynamic, Flags: router used rib nho << next-hop override
   NBMA address: 1.1.24.2 
10.10.3.0/24 via 192.168.1.3
   Tunnel0 created 00:13:30, expire 01:46:29
   Type: dynamic, Flags: router unique local 
   NBMA address: 1.1.34.3 
    (no-socket) 
192.168.1.1/32 via 192.168.1.1
   Tunnel0 created 01:46:24, never expire 
   Type: static, Flags: used 
   NBMA address: 1.1.14.1 
192.168.1.2/32 via 192.168.1.2
   Tunnel0 created 00:13:31, expire 01:46:29
   Type: dynamic, Flags: router implicit 
   NBMA address: 1.1.24.2

DMVPN Phase 3 configuration with BGP

Hub and Spoke routers are using mGRE tunnels
Hub router(s) act as route-reflector server(s)
Spoke routers are route-reflector clients
Hub router can send summary route to Spoke routers
eBGP can also be used by configuring Hub and Spokes in different ASNs. Here we are using iBGP with route-reflector

Configuration:

----------
R1 - Hub:
----------

hostname R1
!
ip cef
!
crypto isakmp policy 10
 encr aes
 authentication pre-share
 group 2
crypto isakmp key DmVpNpR3$h@r3dK3Y address 0.0.0.0        
!
crypto ipsec transform-set TRANSFORM-SET esp-aes esp-sha-hmac 
 mode transport
!
crypto ipsec profile PROTECT-GRE
 set transform-set TRANSFORM-SET 
!
interface Tunnel0
 bandwidth 4096
 ip address 192.168.1.1 255.255.255.0
 no ip redirects
 ip mtu 1400
 ip nhrp authentication NhRp@UtH
 ip nhrp map multicast dynamic
 ip nhrp network-id 100
 ip nhrp redirect
 ip tcp adjust-mss 1360
 tunnel source FastEthernet0/0
 tunnel mode gre multipoint
 tunnel key 123
 tunnel protection ipsec profile PROTECT-GRE
!
interface FastEthernet0/0
 ip address 1.1.14.1 255.255.255.0
!
interface FastEthernet0/1
 ip address 10.10.1.1 255.255.255.0
!
router bgp 65001
 bgp router-id 192.168.1.1
 bgp log-neighbor-changes
 bgp listen range 192.168.1.0/24 peer-group DMVPN-SPOKES
 bgp listen limit 50
 network 10.10.1.0 mask 255.255.255.0
 aggregate-address 10.10.0.0 255.255.0.0 summary-only
 neighbor DMVPN-SPOKES peer-group
 neighbor DMVPN-SPOKES remote-as 65001
 neighbor DMVPN-SPOKES route-reflector-client
!
ip route 0.0.0.0 0.0.0.0 1.1.14.4

------------
R2 - Spoke:
------------

hostname R2
!
ip cef
!
crypto isakmp policy 10
 encr aes
 authentication pre-share
 group 2
crypto isakmp key DmVpNpR3$h@r3dK3Y address 0.0.0.0        
!
crypto ipsec transform-set TRANSFORM-SET esp-aes esp-sha-hmac 
 mode transport
!
crypto ipsec profile PROTECT-GRE
 set transform-set TRANSFORM-SET 
!
interface Tunnel0
 bandwidth 4096
 ip address 192.168.1.2 255.255.255.0
 no ip redirects
 ip mtu 1400
 ip nhrp authentication NhRp@UtH
 ip nhrp map multicast 1.1.14.1
 ip nhrp map 192.168.1.1 1.1.14.1
 ip nhrp network-id 100
 ip nhrp nhs 192.168.1.1
 ip nhrp shortcut
 ip tcp adjust-mss 1360
 tunnel source FastEthernet0/0
 tunnel mode gre multipoint
 tunnel key 123
 tunnel protection ipsec profile PROTECT-GRE
!
interface FastEthernet0/0
 ip address 1.1.24.2 255.255.255.0
!
interface FastEthernet0/1
 ip address 10.10.2.2 255.255.255.0
!
router bgp 65001
 bgp router-id 192.168.1.2
 bgp log-neighbor-changes
 network 10.10.2.0 mask 255.255.255.0
 neighbor 192.168.1.1 remote-as 65001
!
ip route 0.0.0.0 0.0.0.0 1.1.24.4

------------
R3 - Spoke:
------------

hostname R3
!
ip cef
!
crypto isakmp policy 10
 encr aes
 authentication pre-share
 group 2
crypto isakmp key DmVpNpR3$h@r3dK3Y address 0.0.0.0        
!
crypto ipsec transform-set TRANSFORM-SET esp-aes esp-sha-hmac 
 mode transport
!
crypto ipsec profile PROTECT-GRE
 set transform-set TRANSFORM-SET 
!
interface Tunnel0
 bandwidth 4096
 ip address 192.168.1.3 255.255.255.0
 no ip redirects
 ip mtu 1400
 ip nhrp authentication NhRp@UtH
 ip nhrp map multicast 1.1.14.1
 ip nhrp map 192.168.1.1 1.1.14.1
 ip nhrp network-id 100
 ip nhrp nhs 192.168.1.1
 ip nhrp shortcut
 ip tcp adjust-mss 1360
 tunnel source FastEthernet0/0
 tunnel mode gre multipoint
 tunnel key 123
 tunnel protection ipsec profile PROTECT-GRE
!
interface FastEthernet0/0
 ip address 1.1.34.3 255.255.255.0
!
interface FastEthernet0/1
 ip address 10.10.3.3 255.255.255.0
!
router bgp 65001
 bgp router-id 192.168.1.3
 bgp log-neighbor-changes
 network 10.10.3.0 mask 255.255.255.0
 neighbor 192.168.1.1 remote-as 65001
!
ip route 0.0.0.0 0.0.0.0 1.1.34.4

Verification:

- BGP peering between Hub and Spokes only, No spoke to spoke peering

R1#show ip bgp summary 
BGP router identifier 192.168.1.1, local AS number 65001
BGP table version is 8, main routing table version 8
4 network entries using 592 bytes of memory
4 path entries using 256 bytes of memory
3/3 BGP path/bestpath attribute entries using 408 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
BGP using 1256 total bytes of memory
BGP activity 4/0 prefixes, 4/0 paths, scan interval 60 secs

Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
*192.168.1.2    4        65001      18      20        8    0    0 00:12:43        1
*192.168.1.3    4        65001      19      18        8    0    0 00:12:45        1
* Dynamically created based on a listen range command
Dynamically created neighbors: 2, Subnet ranges: 1

BGP peergroup DMVPN-SPOKES listen range group members: 
  192.168.1.0/24 

Total dynamically created neighbors: 2/(50 max), Subnet ranges: 1

R2#show ip bgp summary 
BGP router identifier 192.168.1.2, local AS number 65001
BGP table version is 3, main routing table version 3
2 network entries using 296 bytes of memory
2 path entries using 128 bytes of memory
2/2 BGP path/bestpath attribute entries using 272 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
BGP using 696 total bytes of memory
BGP activity 2/0 prefixes, 2/0 paths, scan interval 60 secs

Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
192.168.1.1     4        65001      20      18        3    0    0 00:12:50        1

R3#show ip bgp summary 
BGP router identifier 192.168.1.3, local AS number 65001
BGP table version is 3, main routing table version 3
2 network entries using 296 bytes of memory
2 path entries using 128 bytes of memory
2/2 BGP path/bestpath attribute entries using 272 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
BGP using 696 total bytes of memory
BGP activity 2/0 prefixes, 2/0 paths, scan interval 60 secs

Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
192.168.1.1     4        65001      19      19        3    0    0 00:12:54        1

- Traffic between Spoke-R2 and Spoke-R3

R2#ping 10.10.3.3 so 10.10.2.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.10.3.3, timeout is 2 seconds:
Packet sent with a source address of 10.10.2.2 
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 124/132/140 ms

R2#trace 10.10.3.3 so 10.10.2.2
Type escape sequence to abort.
Tracing the route to 10.10.3.3
VRF info: (vrf in name/id, vrf out name/id)
  1 192.168.1.3 144 msec *  124 msec         << Spoke R3 Tunnel IP

- DMVPN Status

R1#show dmvpn
Legend: Attrb --> S - Static, D - Dynamic, I - Incomplete
        N - NATed, L - Local, X - No Socket
        # Ent --> Number of NHRP entries with same NBMA peer
        NHS Status: E --> Expecting Replies, R --> Responding, W --> Waiting
        UpDn Time --> Up or Down Time for a Tunnel
======================================================================
Interface: Tunnel0, IPv4 NHRP Details 
Type:Hub, NHRP Peers:2, 

 # Ent  Peer NBMA Addr Peer Tunnel Add State  UpDn Tm Attrb
 ----- --------------- --------------- ----- -------- -----
     1 1.1.24.2            192.168.1.2    UP 00:15:42     D
     1 1.1.34.3            192.168.1.3    UP 00:15:42     D

R2#show dmvpn
Legend: Attrb --> S - Static, D - Dynamic, I - Incomplete
        N - NATed, L - Local, X - No Socket
        # Ent --> Number of NHRP entries with same NBMA peer
        NHS Status: E --> Expecting Replies, R --> Responding, W --> Waiting
        UpDn Time --> Up or Down Time for a Tunnel
======================================================================
Interface: Tunnel0, IPv4 NHRP Details 
Type:Spoke, NHRP Peers:2, 

 # Ent  Peer NBMA Addr Peer Tunnel Add State  UpDn Tm Attrb
 ----- --------------- --------------- ----- -------- -----
     2 1.1.34.3            192.168.1.3    UP 00:01:20   DT1
                           192.168.1.3    UP 00:01:20     D
     1 1.1.14.1            192.168.1.1    UP 00:15:47     S
*T1 - Route Installed

R3#show dmvpn
Legend: Attrb --> S - Static, D - Dynamic, I - Incomplete
        N - NATed, L - Local, X - No Socket
        # Ent --> Number of NHRP entries with same NBMA peer
        NHS Status: E --> Expecting Replies, R --> Responding, W --> Waiting
        UpDn Time --> Up or Down Time for a Tunnel
======================================================================
Interface: Tunnel0, IPv4 NHRP Details 
Type:Spoke, NHRP Peers:2, 

 # Ent  Peer NBMA Addr Peer Tunnel Add State  UpDn Tm Attrb
 ----- --------------- --------------- ----- -------- -----
     2 1.1.24.2            192.168.1.2    UP 00:01:23   DT1
                           192.168.1.2    UP 00:01:23     D
     1 1.1.14.1            192.168.1.1    UP 00:15:49     S
*T1 - Route Installed

- BGP Table

R1#show ip bgp
BGP table version is 8, local router ID is 192.168.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, 
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, 
              x best-external, a additional-path, c RIB-compressed, 
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>  10.10.0.0/16     0.0.0.0                            32768 i
 s>  10.10.1.0/24     0.0.0.0                  0         32768 i
 s>i 10.10.2.0/24     192.168.1.2              0    100      0 i
 s>i 10.10.3.0/24     192.168.1.3              0    100      0 i

R2#show ip bgp
BGP table version is 3, local router ID is 192.168.1.2
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, 
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, 
              x best-external, a additional-path, c RIB-compressed, 
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>i 10.10.0.0/16     192.168.1.1              0    100      0 i
 *>  10.10.2.0/24     0.0.0.0                  0         32768 i

R3#show ip bgp
BGP table version is 3, local router ID is 192.168.1.3
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, 
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, 
              x best-external, a additional-path, c RIB-compressed, 
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>i 10.10.0.0/16     192.168.1.1              0    100      0 i
 *>  10.10.3.0/24     0.0.0.0                  0         32768 i

- Routing Table

R1#show ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area 
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
       + - replicated route, % - next hop override

Gateway of last resort is 1.1.14.4 to network 0.0.0.0

S*    0.0.0.0/0 [1/0] via 1.1.14.4
      1.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        1.1.14.0/24 is directly connected, FastEthernet0/0
L        1.1.14.1/32 is directly connected, FastEthernet0/0
      10.0.0.0/8 is variably subnetted, 5 subnets, 3 masks
B        10.10.0.0/16 [200/0] via 0.0.0.0, 00:17:13, Null0
C        10.10.1.0/24 is directly connected, FastEthernet0/1
L        10.10.1.1/32 is directly connected, FastEthernet0/1
B        10.10.2.0/24 [200/0] via 192.168.1.2, 00:16:05
B        10.10.3.0/24 [200/0] via 192.168.1.3, 00:16:57
      192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks
C        192.168.1.0/24 is directly connected, Tunnel0
L        192.168.1.1/32 is directly connected, Tunnel0

R2#show ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area 
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
       + - replicated route, % - next hop override

Gateway of last resort is 1.1.24.4 to network 0.0.0.0

S*    0.0.0.0/0 [1/0] via 1.1.24.4
      1.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        1.1.24.0/24 is directly connected, FastEthernet0/0
L        1.1.24.2/32 is directly connected, FastEthernet0/0
      10.0.0.0/8 is variably subnetted, 4 subnets, 3 masks
B        10.10.0.0/16 [200/0] via 192.168.1.1, 00:16:11
C        10.10.2.0/24 is directly connected, FastEthernet0/1
L        10.10.2.2/32 is directly connected, FastEthernet0/1
H        10.10.3.0/24 [250/1] via 192.168.1.3, 00:02:52, Tunnel0
      192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks
C        192.168.1.0/24 is directly connected, Tunnel0
L        192.168.1.2/32 is directly connected, Tunnel0

R3#show ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area 
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
       + - replicated route, % - next hop override

Gateway of last resort is 1.1.34.4 to network 0.0.0.0

S*    0.0.0.0/0 [1/0] via 1.1.34.4
      1.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        1.1.34.0/24 is directly connected, FastEthernet0/0
L        1.1.34.3/32 is directly connected, FastEthernet0/0
      10.0.0.0/8 is variably subnetted, 4 subnets, 3 masks
B        10.10.0.0/16 [200/0] via 192.168.1.1, 00:17:06
H        10.10.2.0/24 [250/1] via 192.168.1.2, 00:02:55, Tunnel0
C        10.10.3.0/24 is directly connected, FastEthernet0/1
L        10.10.3.3/32 is directly connected, FastEthernet0/1
      192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks
C        192.168.1.0/24 is directly connected, Tunnel0
L        192.168.1.3/32 is directly connected, Tunnel0

- NHRP Table

R1#show ip nhrp
192.168.1.2/32 via 192.168.1.2
   Tunnel0 created 00:17:49, expire 01:42:10
   Type: dynamic, Flags: unique registered used 
   NBMA address: 1.1.24.2 
192.168.1.3/32 via 192.168.1.3
   Tunnel0 created 00:17:49, expire 01:42:11
   Type: dynamic, Flags: unique registered used 
   NBMA address: 1.1.34.3 

R2#show ip nhrp
10.10.2.0/24 via 192.168.1.2
   Tunnel0 created 00:03:27, expire 01:56:32
   Type: dynamic, Flags: router unique local 
   NBMA address: 1.1.24.2 
    (no-socket) 
10.10.3.0/24 via 192.168.1.3
   Tunnel0 created 00:03:27, expire 01:56:31
   Type: dynamic, Flags: router used rib 
   NBMA address: 1.1.34.3 
192.168.1.1/32 via 192.168.1.1
   Tunnel0 created 00:18:28, never expire 
   Type: static, Flags: used 
   NBMA address: 1.1.14.1 
192.168.1.3/32 via 192.168.1.3
   Tunnel0 created 00:03:28, expire 01:56:32
   Type: dynamic, Flags: router implicit used 
   NBMA address: 1.1.34.3 

R3#show ip nhrp
10.10.2.0/24 via 192.168.1.2
   Tunnel0 created 00:03:29, expire 01:56:30
   Type: dynamic, Flags: router used rib 
   NBMA address: 1.1.24.2 
10.10.3.0/24 via 192.168.1.3
   Tunnel0 created 00:03:30, expire 01:56:29
   Type: dynamic, Flags: router unique local 
   NBMA address: 1.1.34.3 
    (no-socket) 
192.168.1.1/32 via 192.168.1.1
   Tunnel0 created 00:18:31, never expire 
   Type: static, Flags: used 
   NBMA address: 1.1.14.1 
192.168.1.2/32 via 192.168.1.2
   Tunnel0 created 00:03:31, expire 01:56:29
   Type: dynamic, Flags: router implicit used 
   NBMA address: 1.1.24.2

DMVPN Phase 2

March 1, 2017Cisco, DMVPN, VPNBGP, DMVPN, EIGRP, IPSec VPN, mGRE, NHRP, OSPF, Phase 2, Route-reflector, VPNAmolak

Phase 2 – Spoke to Spoke Design

DMVPN Phase 2 design introduced the ability for dynamic spoke-to-spoke tunnels without having the traffic go through the hub. Phase 2 improved on Phase 1 by allowing spokes to build a spoke-to-spoke tunnel on demand with these restrictions:

Spokes must use mGRE (Multipoint GRE) tunnels
Spokes must receive specific routes for all remote spoke subnets
The next hop of the entry in the routing table must list the remote spoke as the next hop

Check these links for

DMVPN basics – http://www.amolak.net/dmvpn-basics/
DMVPN Phase 1 Configuration – http://www.amolak.net/dmvpn-phase-1/

Here is the network topology for DMVPN phase 2 discussion and configuration.

DMVPN Phase 2 configuration with EIGRP

EIGRP Split Horizon Rule – The split horizon rule prohibits a router from advertising a route through an interface that the router itself uses to reach the destination. In DMVPN, Hub router learn route(s) from one spoke via Tunnel0 interface and have to advertise it to other spoke via same Tunnel0 interface. Thus, in order for DMVPN to work in Phase 2 with EIGRP, split horizon must be disabled on the tunnel interface using the “no ip split-horizon eigrp <asn>” command.

Next-hop self in EIGRP – The next hop for all of the routes must point to the remote spoke. This is the key to triggering the generation of a spoke-to-spoke tunnel. To instruct EIGRP to use the received next hop rather than itself, use the “no ip next-hop-self eigrp <asn>” command.

Configuration:

----------
R1 - Hub:
----------

hostname R1
!
ip cef
!
crypto isakmp policy 10
 encr aes
 authentication pre-share
 group 2
crypto isakmp key DmVpNpR3$h@r3dK3Y address 0.0.0.0        
!
!
crypto ipsec transform-set TRANSFORM-SET esp-aes esp-sha-hmac 
 mode transport
!
crypto ipsec profile PROTECT-GRE
 set transform-set TRANSFORM-SET 
!
interface Tunnel0
 bandwidth 4096
 ip address 192.168.1.1 255.255.255.0
 no ip redirects
 ip mtu 1400
 no ip next-hop-self eigrp 100
 no ip split-horizon eigrp 100
 ip nhrp authentication NhRp@UtH
 ip nhrp map multicast dynamic
 ip nhrp network-id 100
 ip tcp adjust-mss 1360
 tunnel source FastEthernet0/0
 tunnel mode gre multipoint
 tunnel key 123
 tunnel protection ipsec profile PROTECT-GRE
!
interface FastEthernet0/0
 ip address 1.1.14.1 255.255.255.0
!
interface FastEthernet0/1
 ip address 10.10.1.1 255.255.255.0
!
router eigrp 100
 network 10.10.1.1 0.0.0.0
 network 192.168.1.1 0.0.0.0
!
ip route 0.0.0.0 0.0.0.0 1.1.14.4

------------
R2 - Spoke:
------------

hostname R2
!
ip cef
!
crypto isakmp policy 10
 encr aes
 authentication pre-share
 group 2
crypto isakmp key DmVpNpR3$h@r3dK3Y address 0.0.0.0        
!
!
crypto ipsec transform-set TRANSFORM-SET esp-aes esp-sha-hmac 
 mode transport
!
crypto ipsec profile PROTECT-GRE
 set transform-set TRANSFORM-SET 
!
interface Tunnel0
 bandwidth 4096
 ip address 192.168.1.2 255.255.255.0
 no ip redirects
 ip mtu 1400
 ip nhrp authentication NhRp@UtH
 ip nhrp map multicast 1.1.14.1
 ip nhrp map 192.168.1.1 1.1.14.1
 ip nhrp network-id 100
 ip nhrp nhs 192.168.1.1
 ip tcp adjust-mss 1360
 tunnel source FastEthernet0/0
 tunnel mode gre multipoint
 tunnel key 123
 tunnel protection ipsec profile PROTECT-GRE
!
interface FastEthernet0/0
 ip address 1.1.24.2 255.255.255.0
!
interface FastEthernet0/1
 ip address 10.10.2.2 255.255.255.0
!
router eigrp 100
 network 10.10.2.2 0.0.0.0
 network 192.168.1.2 0.0.0.0
!
ip route 0.0.0.0 0.0.0.0 1.1.24.4

------------
R3 - Spoke:
------------

hostname R3
!
ip cef
!
crypto isakmp policy 10
 encr aes
 authentication pre-share
 group 2
crypto isakmp key DmVpNpR3$h@r3dK3Y address 0.0.0.0        
!
!
crypto ipsec transform-set TRANSFORM-SET esp-aes esp-sha-hmac 
 mode transport
!
crypto ipsec profile PROTECT-GRE
 set transform-set TRANSFORM-SET 
!
interface Tunnel0
 bandwidth 4096
 ip address 192.168.1.3 255.255.255.0
 no ip redirects
 ip mtu 1400
 ip nhrp authentication NhRp@UtH
 ip nhrp map multicast 1.1.14.1
 ip nhrp map 192.168.1.1 1.1.14.1
 ip nhrp network-id 100
 ip nhrp nhs 192.168.1.1
 ip tcp adjust-mss 1360
 tunnel source FastEthernet0/0
 tunnel mode gre multipoint
 tunnel key 123
 tunnel protection ipsec profile PROTECT-GRE
!
interface FastEthernet0/0
 ip address 1.1.34.3 255.255.255.0
!
interface FastEthernet0/1
 ip address 10.10.3.3 255.255.255.0
!
router eigrp 100
 network 10.10.3.3 0.0.0.0
 network 192.168.1.3 0.0.0.0
!
ip route 0.0.0.0 0.0.0.0 1.1.34.4

---------------
R4 - Internet:
---------------

hostname R4
!
interface FastEthernet0/0
 ip address 1.1.14.4 255.255.255.0
!
interface FastEthernet0/1
 ip address 1.1.24.4 255.255.255.0
!
interface FastEthernet1/0
 ip address 1.1.34.4 255.255.255.0
!

Verification:

- Hub and Spokes routers are using mGRE tunnels

R1#show int t0
Tunnel0 is up, line protocol is up 
  Hardware is Tunnel
  Internet address is 192.168.1.1/24
  MTU 17870 bytes, BW 4096 Kbit/sec, DLY 50000 usec, 
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation TUNNEL, loopback not set
  Keepalive not set
  Tunnel source 1.1.14.1 (FastEthernet0/0)
   Tunnel Subblocks:
      src-track:
         Tunnel0 source tracking subblock associated with FastEthernet0/0
          Set of tunnels with source FastEthernet0/0, 1 member (includes iterators), on interface <OK>
  Tunnel protocol/transport multi-GRE/IP

R2#show int t0
Tunnel0 is up, line protocol is up 
  Hardware is Tunnel
  Internet address is 192.168.1.2/24
  MTU 17870 bytes, BW 4096 Kbit/sec, DLY 50000 usec, 
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation TUNNEL, loopback not set
  Keepalive not set
  Tunnel source 1.1.24.2 (FastEthernet0/0)
   Tunnel Subblocks:
      src-track:
         Tunnel0 source tracking subblock associated with FastEthernet0/0
          Set of tunnels with source FastEthernet0/0, 1 member (includes iterators), on interface <OK>
  Tunnel protocol/transport multi-GRE/IP

R3#show int t0
Tunnel0 is up, line protocol is up 
  Hardware is Tunnel
  Internet address is 192.168.1.3/24
  MTU 17870 bytes, BW 4096 Kbit/sec, DLY 50000 usec, 
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation TUNNEL, loopback not set
  Keepalive not set
  Tunnel source 1.1.34.3 (FastEthernet0/0)
   Tunnel Subblocks:
      src-track:
         Tunnel0 source tracking subblock associated with FastEthernet0/0
          Set of tunnels with source FastEthernet0/0, 1 member (includes iterators), on interface <OK>
  Tunnel protocol/transport multi-GRE/IP

- Routing adjacency (EIGRP neighborship) is between Hub and Spokes only 

R1#show ip eigrp neighbors
EIGRP-IPv4 Neighbors for AS(100)
H   Address                 Interface              Hold Uptime   SRTT   RTO  Q  Seq
                                                   (sec)         (ms)       Cnt Num
1   192.168.1.2             Tu0                      13 05:09:22  201  1206  0  3
0   192.168.1.3             Tu0                      13 05:09:32  167  1002  0  4

R2#show ip eigrp neighbors
EIGRP-IPv4 Neighbors for AS(100)
H   Address                 Interface              Hold Uptime   SRTT   RTO  Q  Seq
                                                   (sec)         (ms)       Cnt Num
0   192.168.1.1             Tu0                      13 05:09:37  140   840  0  6

R3#show ip eigrp neighbors
EIGRP-IPv4 Neighbors for AS(100)
H   Address                 Interface              Hold Uptime   SRTT   RTO  Q  Seq
                                                   (sec)         (ms)       Cnt Num
0   192.168.1.1             Tu0                      11 05:09:49  156   936  0  6

- Routing Table (see next-hop IP on spoke routers to reach other spoke subnets) 

R1#show ip route eigrp | beg Gate
Gateway of last resort is 1.1.14.4 to network 0.0.0.0

      10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
D        10.10.2.0/24 [90/1907456] via 192.168.1.2, 05:11:20, Tunnel0
D        10.10.3.0/24 [90/1907456] via 192.168.1.3, 05:11:30, Tunnel0

R2#show ip route eigrp | beg Gate
Gateway of last resort is 1.1.24.4 to network 0.0.0.0

      10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
D        10.10.1.0/24 [90/1907456] via 192.168.1.1, 05:11:31, Tunnel0
D        10.10.3.0/24 [90/3187456] via 192.168.1.3, 05:11:31, Tunnel0

R3#show ip route eigrp | beg Gate
Gateway of last resort is 1.1.34.4 to network 0.0.0.0

      10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
D        10.10.1.0/24 [90/1907456] via 192.168.1.1, 05:11:42, Tunnel0
D        10.10.2.0/24 [90/3187456] via 192.168.1.2, 05:11:32, Tunnel0

- DMVPN Table
- Hub shows dynamic entries, spokes registered themselves with hub
- Spokes show static entries, static entry defined for hub

R1#show dmvpn
Legend: Attrb --> S - Static, D - Dynamic, I - Incomplete
        N - NATed, L - Local, X - No Socket
        # Ent --> Number of NHRP entries with same NBMA peer
        NHS Status: E --> Expecting Replies, R --> Responding, W --> Waiting
        UpDn Time --> Up or Down Time for a Tunnel
======================================================================
Interface: Tunnel0, IPv4 NHRP Details 
Type:Hub, NHRP Peers:2, 

 # Ent  Peer NBMA Addr Peer Tunnel Add State  UpDn Tm Attrb
 ----- --------------- --------------- ----- -------- -----
     1 1.1.24.2            192.168.1.2    UP 00:51:08     D
     1 1.1.34.3            192.168.1.3    UP 00:51:08     D

R2#show dmvpn
Legend: Attrb --> S - Static, D - Dynamic, I - Incomplete
        N - NATed, L - Local, X - No Socket
        # Ent --> Number of NHRP entries with same NBMA peer
        NHS Status: E --> Expecting Replies, R --> Responding, W --> Waiting
        UpDn Time --> Up or Down Time for a Tunnel
======================================================================
Interface: Tunnel0, IPv4 NHRP Details 
Type:Spoke, NHRP Peers:1, 

 # Ent  Peer NBMA Addr Peer Tunnel Add State  UpDn Tm Attrb
 ----- --------------- --------------- ----- -------- -----
     1 1.1.14.1            192.168.1.1    UP 00:51:28     S

R3#show dmvpn
Legend: Attrb --> S - Static, D - Dynamic, I - Incomplete
        N - NATed, L - Local, X - No Socket
        # Ent --> Number of NHRP entries with same NBMA peer
        NHS Status: E --> Expecting Replies, R --> Responding, W --> Waiting
        UpDn Time --> Up or Down Time for a Tunnel
======================================================================
Interface: Tunnel0, IPv4 NHRP Details 
Type:Spoke, NHRP Peers:1, 

 # Ent  Peer NBMA Addr Peer Tunnel Add State  UpDn Tm Attrb
 ----- --------------- --------------- ----- -------- -----
     1 1.1.14.1            192.168.1.1    UP 00:51:30     S

- Traffic between Spoke R2 and Spoke R3

Routing entry on R2 shows R3 subnet (10.10.3.0/24) is reachable via next-hop IP 192.168.1.3 (R3 Tunnel IP)

D        10.10.3.0/24 [90/3187456] via 192.168.1.3, 00:05:12, Tunnel0

Lets check CEF adjacency for next-hop IP 192.168.1.3

R2#show adjacency 192.168.1.3
Protocol Interface                 Address
IP       Tunnel0                   192.168.1.3(5) (incomplete)

The adjacency is showing incomplete. The incomplete adjacency triggers a CEF punt to the CPU for further processing (to resolve the address).

R2#show ip cef 192.168.1.3 internal 
192.168.1.0/24, epoch 0, flags attached, connected, cover dependents, need deagg, RIB[C], refcount 5, per-destination sharing
  sources: RIB 
  feature space:
   IPRM: 0x0003800C
  subblocks:
   gsb Connected chain head(1): 0x6A36ADFC
   Covered dependent prefixes: 3
     need deagg: 2
     notify cover updated: 1
  ifnums:
   Tunnel0(6)
  path 695C0994, path list 6A90BBB8, share 1/1, type connected prefix, for IPv4
  connected to Tunnel0, adjacency punt
  output chain: punt

This causes R2(Spoke) to send a resolution request to R1(Hub) for Spoke-R3’s NBMA address. The request gets forwarded from R1(Hub) to Spoke-R3. Spoke-R3 replies directly to Spoke-R2 with its mapping information. During this process, R2(Spoke) will send the actual data packet to R1(Hub) to be delivered to R3(Spoke) as a last-ditch effort to not drop the traffic. The first traceroute will look as below, the traffic traverse via hub.

R2#traceroute 10.10.3.3 so 10.10.2.2
Type escape sequence to abort.
Tracing the route to 10.10.3.3
VRF info: (vrf in name/id, vrf out name/id)
  1 192.168.1.1 180 msec 128 msec 152 msec    << Hub R1 Tunnel IP
  2 192.168.1.3 252 msec

- Debug nhrp packet shows following events:

Spoke-R2 sends resolution request via Tunnel0, it will reach to Hub-R1 as this is the only active tunnel on R2 at this moment. 
R2#
*Mar  1 00:29:49.567: NHRP: Send Resolution Request via Tunnel0 vrf 0, packet size: 88
*Mar  1 00:29:49.575:  src: 192.168.1.2, dst: 192.168.1.3
*Mar  1 00:29:49.583:  (F) afn: AF_IP(1), type: IP(800), hop: 255, ver: 1
*Mar  1 00:29:49.583:      shtl: 4(NSAP), sstl: 0(NSAP)
*Mar  1 00:29:49.587:      pktsz: 88 extoff: 52
*Mar  1 00:29:49.591:  (M) flags: "router auth src-stable nat ", reqid: 2 
*Mar  1 00:29:49.595:      src NBMA: 1.1.24.2
*Mar  1 00:29:49.595:      src protocol: 192.168.1.2, dst protocol: 192.168.1.3
*Mar  1 00:29:49.603:  (C-1) code: no error(0)
*Mar  1 00:29:49.603:        prefix: 32, mtu: 17870, hd_time: 7200
*Mar  1 00:29:49.603:        addr_len: 0(NSAP), subaddr_len: 0(NSAP), proto_len: 0, pref: 0

This request arrives at Hub-R1. Hub-R1 finds it is destined for destination IP 192.168.1.3 and Hub-R1 will forward it to Spoke-R3.  
R1#
*Mar  1 00:29:49.683: NHRP: Receive Resolution Request via Tunnel0 vrf 0, packet size: 88
*Mar  1 00:29:49.687:  (F) afn: AF_IP(1), type: IP(800), hop: 255, ver: 1
*Mar  1 00:29:49.691:      shtl: 4(NSAP), sstl: 0(NSAP)
*Mar  1 00:29:49.695:      pktsz: 88 extoff: 52
*Mar  1 00:29:49.695:  (M) flags: "router auth src-stable nat ", reqid: 2 
*Mar  1 00:29:49.699:      src NBMA: 1.1.24.2
*Mar  1 00:29:49.703:      src protocol: 192.168.1.2, dst protocol: 192.168.1.3
*Mar  1 00:29:49.707:  (C-1) code: no error(0)
*Mar  1 00:29:49.707:        prefix: 32, mtu: 17870, hd_time: 7200
*Mar  1 00:29:49.707:        addr_len: 0(NSAP), subaddr_len: 0(NSAP), proto_len: 0, pref: 0
*Mar  1 00:29:49.715: NHRP: Forwarding Resolution Request via Tunnel0 vrf 0, packet size: 108
*Mar  1 00:29:49.719:  src: 192.168.1.1, dst: 192.168.1.3
*Mar  1 00:29:49.723:  (F) afn: AF_IP(1), type: IP(800), hop: 254, ver: 1
*Mar  1 00:29:49.723:      shtl: 4(NSAP), sstl: 0(NSAP)
*Mar  1 00:29:49.723:     
R1# pktsz: 108 extoff: 52
*Mar  1 00:29:49.723:  (M) flags: "router auth src-stable nat ", reqid: 2 
*Mar  1 00:29:49.723:      src NBMA: 1.1.24.2
*Mar  1 00:29:49.723:      src protocol: 192.168.1.2, dst protocol: 192.168.1.3
*Mar  1 00:29:49.723:  (C-1) code: no error(0)
*Mar  1 00:29:49.723:        prefix: 32, mtu: 17870, hd_time: 7200
*Mar  1 00:29:49.723:        addr_len: 0(NSAP), subaddr_len: 0(NSAP), proto_len: 0, pref: 0

Then Spoke-R3 receives NHRP resolution request. This request contains Spoke-R2's details including NBMA and Tunnel IP of Spoke-R2. Spoke-R3 would initiate a direct DMVPN tunnel to R2 and send reply to R2.

R3#
*Mar  1 00:29:49.671: NHRP: Receive Resolution Request via Tunnel0 vrf 0, packet size: 108
*Mar  1 00:29:49.675:  (F) afn: AF_IP(1), type: IP(800), hop: 254, ver: 1
*Mar  1 00:29:49.675:      shtl: 4(NSAP), sstl: 0(NSAP)
*Mar  1 00:29:49.675:      pktsz: 108 extoff: 52
*Mar  1 00:29:49.675:  (M) flags: "router auth src-stable nat ", reqid: 2 
*Mar  1 00:29:49.675:      src NBMA: 1.1.24.2
*Mar  1 00:29:49.675:      src protocol: 192.168.1.2, dst protocol: 192.168.1.3
*Mar  1 00:29:49.675:  (C-1) code: no error(0)
*Mar  1 00:29:49.675:        prefix: 32, mtu: 17870, hd_time: 7200
*Mar  1 00:29:49.675:        addr_len: 0(NSAP), subaddr_len: 0(NSAP), proto_len: 0, pref: 0
*Mar  1 00:29:50.487: NHRP: Send Resolution Reply via Tunnel0 vrf 0, packet size: 136
*Mar  1 00:29:50.487:  src: 192.168.1.3, dst: 192.168.1.2
*Mar  1 00:29:50.487:  (F) afn: AF_IP(1), type: IP(800), hop: 255, ver: 1
*Mar  1 00:29:50.487:      shtl: 4(NSAP), sstl: 0(NSAP)
*Mar  1 00:29:50.487:      pktsz
R3#: 136 extoff: 60
*Mar  1 00:29:50.487:  (M) flags: "router auth dst-stable unique src-stable nat ", reqid: 2 
*Mar  1 00:29:50.487:      src NBMA: 1.1.24.2
*Mar  1 00:29:50.487:      src protocol: 192.168.1.2, dst protocol: 192.168.1.3
*Mar  1 00:29:50.487:  (C-1) code: no error(0)
*Mar  1 00:29:50.487:        prefix: 32, mtu: 17870, hd_time: 7200
*Mar  1 00:29:50.487:        addr_len: 4(NSAP), subaddr_len: 0(NSAP), proto_len: 4, pref: 0
*Mar  1 00:29:50.487:        client NBMA: 1.1.34.3
*Mar  1 00:29:50.487:        client protocol: 192.168.1.3

R2 receives reply and at this moment both R2 and R3 knows each other's NBMA IP and have direct dmvpn tunnel.

R2#
*Mar  1 00:29:50.635: NHRP: Receive Resolution Reply via Tunnel0 vrf 0, packet size: 136
*Mar  1 00:29:50.643:  (F) afn: AF_IP(1), type: IP(800), hop: 255, ver: 1
*Mar  1 00:29:50.647:      shtl: 4(NSAP), sstl: 0(NSAP)
*Mar  1 00:29:50.647:      pktsz: 136 extoff: 60
*Mar  1 00:29:50.651:  (M) flags: "router auth dst-stable unique src-stable nat ", reqid: 2 
*Mar  1 00:29:50.655:      src NBMA: 1.1.24.2
*Mar  1 00:29:50.655:      src protocol: 192.168.1.2, dst protocol: 192.168.1.3
*Mar  1 00:29:50.663:  (C-1) code: no error(0)
*Mar  1 00:29:50.663:        prefix: 32, mtu: 17870, hd_time: 7200
*Mar  1 00:29:50.663:        addr_len: 4(NSAP), subaddr_len: 0(NSAP), proto_len: 4, pref: 0
*Mar  1 00:29:50.663:        client NBMA: 1.1.34.3
*Mar  1 00:29:50.663:        client protocol: 192.168.1.3 *  140 msec

- Check DMVPN status now

R1#show dmvpn
Legend: Attrb --> S - Static, D - Dynamic, I - Incomplete
        N - NATed, L - Local, X - No Socket
        # Ent --> Number of NHRP entries with same NBMA peer
        NHS Status: E --> Expecting Replies, R --> Responding, W --> Waiting
        UpDn Time --> Up or Down Time for a Tunnel
=====================================================================
Interface: Tunnel0, IPv4 NHRP Details 
Type:Hub, NHRP Peers:2, 

 # Ent  Peer NBMA Addr Peer Tunnel Add State  UpDn Tm Attrb
 ----- --------------- --------------- ----- -------- -----
     1 1.1.24.2            192.168.1.2    UP 05:15:09     D
     1 1.1.34.3            192.168.1.3    UP 05:15:19     D

R2#show dmvpn
Legend: Attrb --> S - Static, D - Dynamic, I - Incomplete
        N - NATed, L - Local, X - No Socket
        # Ent --> Number of NHRP entries with same NBMA peer
        NHS Status: E --> Expecting Replies, R --> Responding, W --> Waiting
        UpDn Time --> Up or Down Time for a Tunnel
======================================================================
Interface: Tunnel0, IPv4 NHRP Details 
Type:Spoke, NHRP Peers:2, 

 # Ent  Peer NBMA Addr Peer Tunnel Add State  UpDn Tm Attrb
 ----- --------------- --------------- ----- -------- -----
     1 1.1.14.1            192.168.1.1    UP 05:15:26     S
     1 1.1.34.3            192.168.1.3    UP 00:34:02     D

R3#show dmvpn
Legend: Attrb --> S - Static, D - Dynamic, I - Incomplete
        N - NATed, L - Local, X - No Socket
        # Ent --> Number of NHRP entries with same NBMA peer
        NHS Status: E --> Expecting Replies, R --> Responding, W --> Waiting
        UpDn Time --> Up or Down Time for a Tunnel
======================================================================
Interface: Tunnel0, IPv4 NHRP Details 
Type:Spoke, NHRP Peers:2, 

 # Ent  Peer NBMA Addr Peer Tunnel Add State  UpDn Tm Attrb
 ----- --------------- --------------- ----- -------- -----
     1 1.1.14.1            192.168.1.1    UP 05:15:51     S
     1 1.1.24.2            192.168.1.2    UP 00:34:17     D

- NHRP State

R1#show ip nhrp
192.168.1.2/32 via 192.168.1.2
   Tunnel0 created 05:16:06, expire 01:23:19
   Type: dynamic, Flags: unique registered used 
   NBMA address: 1.1.24.2 
192.168.1.3/32 via 192.168.1.3
   Tunnel0 created 05:16:16, expire 01:23:19
   Type: dynamic, Flags: unique registered used 
   NBMA address: 1.1.34.3 

R2#show ip nhrp               
192.168.1.1/32 via 192.168.1.1
   Tunnel0 created 05:17:28, never expire 
   Type: static, Flags: used 
   NBMA address: 1.1.14.1 
192.168.1.2/32 via 192.168.1.2
   Tunnel0 created 00:35:19, expire 01:24:40
   Type: dynamic, Flags: router unique local 
   NBMA address: 1.1.24.2 
    (no-socket) 
192.168.1.3/32 via 192.168.1.3
   Tunnel0 created 00:35:20, expire 01:24:40
   Type: dynamic, Flags: router used 
   NBMA address: 1.1.34.3 

R3#show ip nhrp
192.168.1.1/32 via 192.168.1.1
   Tunnel0 created 05:17:14, never expire 
   Type: static, Flags: used 
   NBMA address: 1.1.14.1 
192.168.1.2/32 via 192.168.1.2
   Tunnel0 created 00:35:06, expire 01:24:34
   Type: dynamic, Flags: router used 
   NBMA address: 1.1.24.2 
192.168.1.3/32 via 192.168.1.3
   Tunnel0 created 00:35:05, expire 01:24:34
   Type: dynamic, Flags: router unique local 
   NBMA address: 1.1.34.3 
    (no-socket)

- Ping and traceroute between Spoke-R2 and Spoke-R3
- Now traffic is going through direct spoke-to-spoke tunnel

R2#ping 10.10.3.3 so 10.10.2.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.10.3.3, timeout is 2 seconds:
Packet sent with a source address of 10.10.2.2 
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 116/128/136 ms

R2#trace 10.10.3.3 so 10.10.2.2
Type escape sequence to abort.
Tracing the route to 10.10.3.3
VRF info: (vrf in name/id, vrf out name/id)
  1 192.168.1.3 156 msec *  144 msec         << R3 Tunnel0 IP

- CEF would look as below after direct spoke-to-spoke DMVPN tunnel creation

R2#show adjacency 192.168.1.3
Protocol Interface                 Address
IP       Tunnel0                   192.168.1.3(11)

R2#show ip cef 192.168.1.3 internal
192.168.1.3/32, epoch 0, flags attached, refcount 5, per-destination sharing
  sources: Adj 
  subblocks:
   Adj source: IP midchain out of Tunnel0, addr 192.168.1.3 6AFD37A0
    Dependent covered prefix type adjfib, cover 192.168.1.0/24
  ifnums:
   Tunnel0(6): 192.168.1.3
  path 6AFD6068, path list 6AFD78A0, share 1/1, type adjacency prefix, for IPv4
  attached to Tunnel0, adjacency IP midchain out of Tunnel0, addr 192.168.1.3 6AFD37A0
  output chain: IP midchain out of Tunnel0, addr 192.168.1.3 6AFD37A0 IP adj out of FastEthernet0/0, addr 1.1.24.4 69237240
R2#

DMVPN Phase 2 configuration with OSPF

Configure Hub router as DR. If there is 2nd hub for redundancy, 2nd hub will be BDR.
Configure Spokes routers with ospf priority as ZERO so that they should not participate in DR election and always act as DROTHER.
All spoke routers will have OSPF adjacencies with DR and BDR only.

Configuration:

---------
R1 - Hub:
---------

hostname R1
!
ip cef
!
crypto isakmp policy 10
 encr aes
 authentication pre-share
 group 2
crypto isakmp key DmVpNpR3$h@r3dK3Y address 0.0.0.0        
!
!
crypto ipsec transform-set TRANSFORM-SET esp-aes esp-sha-hmac 
 mode transport
!
crypto ipsec profile PROTECT-GRE
 set transform-set TRANSFORM-SET 
!
interface Tunnel0
 bandwidth 4096
 ip address 192.168.1.1 255.255.255.0
 no ip redirects
 ip mtu 1400
 ip nhrp authentication NhRp@UtH
 ip nhrp map multicast dynamic
 ip nhrp network-id 100
 ip tcp adjust-mss 1360
 ip ospf network broadcast
 ip ospf priority 255
 tunnel source FastEthernet0/0
 tunnel mode gre multipoint
 tunnel key 123
 tunnel protection ipsec profile PROTECT-GRE
!
interface FastEthernet0/0
 ip address 1.1.14.1 255.255.255.0
!
interface FastEthernet0/1
 ip address 10.10.1.1 255.255.255.0
!
router ospf 1
 network 10.10.1.1 0.0.0.0 area 0
 network 192.168.1.1 0.0.0.0 area 0
!
ip route 0.0.0.0 0.0.0.0 1.1.14.4

------------
R2 - Spoke:
------------

hostname R2
!
ip cef
!
crypto isakmp policy 10
 encr aes
 authentication pre-share
 group 2
crypto isakmp key DmVpNpR3$h@r3dK3Y address 0.0.0.0        
!
!
crypto ipsec transform-set TRANSFORM-SET esp-aes esp-sha-hmac 
 mode transport
!
crypto ipsec profile PROTECT-GRE
 set transform-set TRANSFORM-SET 
!
interface Tunnel0
 bandwidth 4096
 ip address 192.168.1.2 255.255.255.0
 no ip redirects
 ip mtu 1400
 ip nhrp authentication NhRp@UtH
 ip nhrp map multicast 1.1.14.1
 ip nhrp map 192.168.1.1 1.1.14.1
 ip nhrp network-id 100
 ip nhrp nhs 192.168.1.1
 ip tcp adjust-mss 1360
 ip ospf network broadcast
 ip ospf priority 0
 tunnel source FastEthernet0/0
 tunnel mode gre multipoint
 tunnel key 123
 tunnel protection ipsec profile PROTECT-GRE
!
interface FastEthernet0/0
 ip address 1.1.24.2 255.255.255.0
!
interface FastEthernet0/1
 ip address 10.10.2.2 255.255.255.0
!
router ospf 1
 network 10.10.2.2 0.0.0.0 area 0
 network 192.168.1.2 0.0.0.0 area 0
!
ip route 0.0.0.0 0.0.0.0 1.1.24.4

------------
R3 - Spoke:
------------

hostname R3
!
ip cef
!
crypto isakmp policy 10
 encr aes
 authentication pre-share
 group 2
crypto isakmp key DmVpNpR3$h@r3dK3Y address 0.0.0.0        
!
!
crypto ipsec transform-set TRANSFORM-SET esp-aes esp-sha-hmac 
 mode transport
!
crypto ipsec profile PROTECT-GRE
 set transform-set TRANSFORM-SET 
!
interface Tunnel0
 bandwidth 4096
 ip address 192.168.1.3 255.255.255.0
 no ip redirects
 ip mtu 1400
 ip nhrp authentication NhRp@UtH
 ip nhrp map multicast 1.1.14.1
 ip nhrp map 192.168.1.1 1.1.14.1
 ip nhrp network-id 100
 ip nhrp nhs 192.168.1.1
 ip tcp adjust-mss 1360
 ip ospf network broadcast
 ip ospf priority 0
 tunnel source FastEthernet0/0
 tunnel mode gre multipoint
 tunnel key 123
 tunnel protection ipsec profile PROTECT-GRE
!
interface FastEthernet0/0
 ip address 1.1.34.3 255.255.255.0
!
interface FastEthernet0/1
 ip address 10.10.3.3 255.255.255.0
!
router ospf 1
 network 10.10.3.3 0.0.0.0 area 0
 network 192.168.1.3 0.0.0.0 area 0
!
ip route 0.0.0.0 0.0.0.0 1.1.34.4
!

Verification:

- OSPF Tunnel Network Type

R1#show ip ospf int t0
Tunnel0 is up, line protocol is up 
  Internet Address 192.168.1.1/24, Area 0, Attached via Network Statement
  Process ID 1, Router ID 192.168.1.1, Network Type BROADCAST, Cost: 24
  Topology-MTID    Cost    Disabled    Shutdown      Topology Name
        0           24        no          no            Base
  Transmit Delay is 1 sec, State DR, Priority 255
  Designated Router (ID) 192.168.1.1, Interface address 192.168.1.1
  No backup designated router on this network
  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
    oob-resync timeout 40
    Hello due in 00:00:04
  Supports Link-local Signaling (LLS)
  Cisco NSF helper support enabled
  IETF NSF helper support enabled
  Index 2/2, flood queue length 0
  Next 0x0(0)/0x0(0)
  Last flood scan length is 1, maximum is 1
  Last flood scan time is 4 msec, maximum is 4 msec
  Neighbor Count is 2, Adjacent neighbor count is 2 
    Adjacent with neighbor 192.168.1.2
    Adjacent with neighbor 192.168.1.3
  Suppress hello for 0 neighbor(s)

R2#show ip ospf int t0
Tunnel0 is up, line protocol is up 
  Internet Address 192.168.1.2/24, Area 0, Attached via Network Statement
  Process ID 1, Router ID 192.168.1.2, Network Type BROADCAST, Cost: 24
  Topology-MTID    Cost    Disabled    Shutdown      Topology Name
        0           24        no          no            Base
  Transmit Delay is 1 sec, State DROTHER, Priority 0
  Designated Router (ID) 192.168.1.1, Interface address 192.168.1.1
  No backup designated router on this network
  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
    oob-resync timeout 40
    Hello due in 00:00:01
  Supports Link-local Signaling (LLS)
  Cisco NSF helper support enabled
  IETF NSF helper support enabled
  Index 2/2, flood queue length 0
  Next 0x0(0)/0x0(0)
  Last flood scan length is 1, maximum is 1
  Last flood scan time is 4 msec, maximum is 4 msec
  Neighbor Count is 1, Adjacent neighbor count is 1 
    Adjacent with neighbor 192.168.1.1  (Designated Router)
  Suppress hello for 0 neighbor(s)

R3#show ip ospf int t0
Tunnel0 is up, line protocol is up 
  Internet Address 192.168.1.3/24, Area 0, Attached via Network Statement
  Process ID 1, Router ID 192.168.1.3, Network Type BROADCAST, Cost: 24
  Topology-MTID    Cost    Disabled    Shutdown      Topology Name
        0           24        no          no            Base
  Transmit Delay is 1 sec, State DROTHER, Priority 0
  Designated Router (ID) 192.168.1.1, Interface address 192.168.1.1
  No backup designated router on this network
  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
    oob-resync timeout 40
    Hello due in 00:00:07
  Supports Link-local Signaling (LLS)
  Cisco NSF helper support enabled
  IETF NSF helper support enabled
  Index 2/2, flood queue length 0
  Next 0x0(0)/0x0(0)
  Last flood scan length is 1, maximum is 1
  Last flood scan time is 4 msec, maximum is 4 msec
  Neighbor Count is 1, Adjacent neighbor count is 1 
    Adjacent with neighbor 192.168.1.1  (Designated Router)
  Suppress hello for 0 neighbor(s)

- OSPF Adjacencies

R1#show ip ospf neighbor 
Neighbor ID     Pri   State           Dead Time   Address         Interface
192.168.1.2       0   FULL/DROTHER    00:00:32    192.168.1.2     Tunnel0
192.168.1.3       0   FULL/DROTHER    00:00:32    192.168.1.3     Tunnel0

R2#show ip ospf neighbor 
Neighbor ID     Pri   State           Dead Time   Address         Interface
192.168.1.1     255   FULL/DR         00:00:31    192.168.1.1     Tunnel0

R3#show ip ospf neighbor 
Neighbor ID     Pri   State           Dead Time   Address         Interface
192.168.1.1     255   FULL/DR         00:00:39    192.168.1.1     Tunnel0

- Routing Table

R1#show ip route ospf | beg Gate
Gateway of last resort is 1.1.14.4 to network 0.0.0.0

      10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
O        10.10.2.0/24 [110/25] via 192.168.1.2, 00:25:23, Tunnel0
O        10.10.3.0/24 [110/25] via 192.168.1.3, 00:25:23, Tunnel0

R2#show ip route ospf | beg Gate
Gateway of last resort is 1.1.24.4 to network 0.0.0.0

      10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
O        10.10.1.0/24 [110/25] via 192.168.1.1, 00:25:28, Tunnel0
O        10.10.3.0/24 [110/25] via 192.168.1.3, 00:25:18, Tunnel0

R3#show ip route ospf | beg Gate
Gateway of last resort is 1.1.34.4 to network 0.0.0.0

      10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
O        10.10.1.0/24 [110/25] via 192.168.1.1, 00:25:30, Tunnel0
O        10.10.2.0/24 [110/25] via 192.168.1.2, 00:25:30, Tunnel0

- Traffic between Spoke R2 and Spoke R3

R2#ping 10.10.3.3 so 10.10.2.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.10.3.3, timeout is 2 seconds:
Packet sent with a source address of 10.10.2.2 
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 116/123/128 ms

R2#trace 10.10.3.3 so 10.10.2.2
Type escape sequence to abort.
Tracing the route to 10.10.3.3
VRF info: (vrf in name/id, vrf out name/id)
  1 192.168.1.3 144 msec *  128 msec         << R3 Tunnel IP

DMVPN Phase 2 configuration with BGP

Hub router would be BGP Route-Reflector server
Spoke routers would be BGP Route-Reflector clients
All tunnels would be mGRE
You can use eBGP also, where Hub and Spoke routers could be configured in different autonomous system number (ASN). Here we will use iBGP only.

-----------
R1 - Hub:
-----------

hostname R1
!
ip cef
!
crypto isakmp policy 10
 encr aes
 authentication pre-share
 group 2
crypto isakmp key DmVpNpR3$h@r3dK3Y address 0.0.0.0        
!
!
crypto ipsec transform-set TRANSFORM-SET esp-aes esp-sha-hmac 
 mode transport
!
crypto ipsec profile PROTECT-GRE
 set transform-set TRANSFORM-SET 
!
interface Tunnel0
 bandwidth 4096
 ip address 192.168.1.1 255.255.255.0
 no ip redirects
 ip mtu 1400
 ip nhrp authentication NhRp@UtH
 ip nhrp map multicast dynamic
 ip nhrp network-id 100
 ip tcp adjust-mss 1360
 tunnel source FastEthernet0/0
 tunnel mode gre multipoint
 tunnel key 123
 tunnel protection ipsec profile PROTECT-GRE
!
interface FastEthernet0/0
 ip address 1.1.14.1 255.255.255.0
!
interface FastEthernet0/1
 ip address 10.10.1.1 255.255.255.0
!
router bgp 65001
 bgp router-id 192.168.1.1
 bgp log-neighbor-changes
 bgp listen range 192.168.1.0/24 peer-group DMVPN-SPOKES
 bgp listen limit 50
 network 10.10.1.0 mask 255.255.255.0
 neighbor DMVPN-SPOKES peer-group
 neighbor DMVPN-SPOKES remote-as 65001
 neighbor DMVPN-SPOKES route-reflector-client
!
ip route 0.0.0.0 0.0.0.0 1.1.14.4

------------
R2 - Spoke:
------------

hostname R2
!
ip cef
!
crypto isakmp policy 10
 encr aes
 authentication pre-share
 group 2
crypto isakmp key DmVpNpR3$h@r3dK3Y address 0.0.0.0        
!
!
crypto ipsec transform-set TRANSFORM-SET esp-aes esp-sha-hmac 
 mode transport
!
crypto ipsec profile PROTECT-GRE
 set transform-set TRANSFORM-SET 
!
interface Tunnel0
 bandwidth 4096
 ip address 192.168.1.2 255.255.255.0
 no ip redirects
 ip mtu 1400
 ip nhrp authentication NhRp@UtH
 ip nhrp map multicast 1.1.14.1
 ip nhrp map 192.168.1.1 1.1.14.1
 ip nhrp network-id 100
 ip nhrp nhs 192.168.1.1
 ip tcp adjust-mss 1360
 tunnel source FastEthernet0/0
 tunnel mode gre multipoint
 tunnel key 123
 tunnel protection ipsec profile PROTECT-GRE
!
interface FastEthernet0/0
 ip address 1.1.24.2 255.255.255.0
!
interface FastEthernet0/1
 ip address 10.10.2.2 255.255.255.0
!
router bgp 65001
 bgp router-id 192.168.1.2
 bgp log-neighbor-changes
 network 10.10.2.0 mask 255.255.255.0
 neighbor 192.168.1.1 remote-as 65001
!
ip route 0.0.0.0 0.0.0.0 1.1.24.4

------------
R3 - Spoke:
------------

hostname R3
!
ip cef
!
crypto isakmp policy 10
 encr aes
 authentication pre-share
 group 2
crypto isakmp key DmVpNpR3$h@r3dK3Y address 0.0.0.0        
!
!
crypto ipsec transform-set TRANSFORM-SET esp-aes esp-sha-hmac 
 mode transport
!
crypto ipsec profile PROTECT-GRE
 set transform-set TRANSFORM-SET 
!
interface Tunnel0
 bandwidth 4096
 ip address 192.168.1.3 255.255.255.0
 no ip redirects
 ip mtu 1400
 ip nhrp authentication NhRp@UtH
 ip nhrp map multicast 1.1.14.1
 ip nhrp map 192.168.1.1 1.1.14.1
 ip nhrp network-id 100
 ip nhrp nhs 192.168.1.1
 ip tcp adjust-mss 1360
 tunnel source FastEthernet0/0
 tunnel mode gre multipoint
 tunnel key 123
 tunnel protection ipsec profile PROTECT-GRE
!
interface FastEthernet0/0
 ip address 1.1.34.3 255.255.255.0
!
interface FastEthernet0/1
 ip address 10.10.3.3 255.255.255.0
!
router bgp 65001
 bgp router-id 192.168.1.3
 bgp log-neighbor-changes
 network 10.10.3.0 mask 255.255.255.0
 neighbor 192.168.1.1 remote-as 65001
!
ip route 0.0.0.0 0.0.0.0 1.1.34.4

Verification:

- BGP Neighborship between Hub and Spokes only

R1#show ip bgp sum
BGP router identifier 192.168.1.1, local AS number 65001
BGP table version is 4, main routing table version 4
3 network entries using 444 bytes of memory
3 path entries using 192 bytes of memory
2/2 BGP path/bestpath attribute entries using 272 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
BGP using 908 total bytes of memory
BGP activity 3/0 prefixes, 3/0 paths, scan interval 60 secs

Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
*192.168.1.2    4        65001      11      15        4    0    0 00:06:11        1
*192.168.1.3    4        65001      12      13        4    0    0 00:06:21        1
* Dynamically created based on a listen range command
Dynamically created neighbors: 2, Subnet ranges: 1

BGP peergroup DMVPN-SPOKES listen range group members: 
  192.168.1.0/24 

Total dynamically created neighbors: 2/(50 max), Subnet ranges: 1

R2#show ip bgp sum
BGP router identifier 192.168.1.2, local AS number 65001
BGP table version is 4, main routing table version 4
3 network entries using 444 bytes of memory
3 path entries using 192 bytes of memory
2/2 BGP path/bestpath attribute entries using 272 bytes of memory
1 BGP rrinfo entries using 24 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
BGP using 932 total bytes of memory
BGP activity 3/0 prefixes, 3/0 paths, scan interval 60 secs

Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
192.168.1.1     4        65001      15      11        4    0    0 00:06:17        2

R3#show ip bgp sum
BGP router identifier 192.168.1.3, local AS number 65001
BGP table version is 4, main routing table version 4
3 network entries using 444 bytes of memory
3 path entries using 192 bytes of memory
2/2 BGP path/bestpath attribute entries using 272 bytes of memory
1 BGP rrinfo entries using 24 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
BGP using 932 total bytes of memory
BGP activity 3/0 prefixes, 3/0 paths, scan interval 60 secs

Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
192.168.1.1     4        65001      13      12        4    0    0 00:06:29        2

- BGP Table

R1#show ip bgp
BGP table version is 4, local router ID is 192.168.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, 
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, 
              x best-external, a additional-path, c RIB-compressed, 
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>  10.10.1.0/24     0.0.0.0                  0         32768 i
 *>i 10.10.2.0/24     192.168.1.2              0    100      0 i
 *>i 10.10.3.0/24     192.168.1.3              0    100      0 i

R2#show ip bgp
BGP table version is 4, local router ID is 192.168.1.2
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, 
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, 
              x best-external, a additional-path, c RIB-compressed, 
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>i 10.10.1.0/24     192.168.1.1              0    100      0 i
 *>  10.10.2.0/24     0.0.0.0                  0         32768 i
 *>i 10.10.3.0/24     192.168.1.3              0    100      0 i

R3#show ip bgp
BGP table version is 4, local router ID is 192.168.1.3
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, 
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, 
              x best-external, a additional-path, c RIB-compressed, 
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>i 10.10.1.0/24     192.168.1.1              0    100      0 i
 *>i 10.10.2.0/24     192.168.1.2              0    100      0 i
 *>  10.10.3.0/24     0.0.0.0                  0         32768 i

- Routing Table

R1#show ip route bgp | beg Gate
Gateway of last resort is 1.1.14.4 to network 0.0.0.0

      10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
B        10.10.2.0/24 [200/0] via 192.168.1.2, 00:07:09
B        10.10.3.0/24 [200/0] via 192.168.1.3, 00:08:11

R2#show ip route bgp | beg Gate
Gateway of last resort is 1.1.24.4 to network 0.0.0.0

      10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
B        10.10.1.0/24 [200/0] via 192.168.1.1, 00:07:16
B        10.10.3.0/24 [200/0] via 192.168.1.3, 00:07:16

R3#show ip route bgp | beg Gate
Gateway of last resort is 1.1.34.4 to network 0.0.0.0

      10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
B        10.10.1.0/24 [200/0] via 192.168.1.1, 00:08:20
B        10.10.2.0/24 [200/0] via 192.168.1.2, 00:07:18

- Traffic between Spoke R2 and Spoke R3

R2#ping 10.10.3.3 so 10.10.2.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.10.3.3, timeout is 2 seconds:
Packet sent with a source address of 10.10.2.2 
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 108/120/128 ms

R2#trace 10.10.3.3 so 10.10.2.2
Type escape sequence to abort.
Tracing the route to 10.10.3.3
VRF info: (vrf in name/id, vrf out name/id)
  1 192.168.1.3 132 msec *  120 msec        << R3 Tunnel IP

DMVPN Phase 2 deployment provides direct spoke-to-spoke tunnels, but one of the limitations is maintaining full routing tables on the spokes. Each route for remote spoke networks needs to be a specific route with the next hop pointing to the remote spoke’s tunnel address. This prevents the hub from being able to send down a summarized route to the spokes for a more concise routing table. This limitation is addressed in DMVPN Phase 3 design, which we will discuss later.

DMVPN Phase 1

February 23, 2017Cisco, DMVPN, VPNBGP, DMVPN, EIGRP, GRE, IPSec VPN, mGRE, NHRP, OSPF, Phase 1, Route-reflector, VPNAmolak

DMVPN Phase 1 – Hub to Spoke Design

DMVPN Phase 1 provides Hub and Spoke tunnel deployment. It means GRE tunnels are only built between Hub and Spokes. There is no spoke-to-spoke tunnel. Traffic from one spoke site to another spoke site always traverse via hub.

Check this link for DMVPN basics – http://www.amolak.net/dmvpn-basics/

We will discuss DMVPN Phase 1 configuration with:

EIGRP
OSPF
BGP

Here is the network topology for our discussion and configuration.

Initial configuration on devices

Site-1 Router R1:

hostname R1
!
ip cef
!
crypto isakmp policy 10
 encr aes
 authentication pre-share
 group 2
crypto isakmp key DmVpNpR3$h@r3dK3Y address 0.0.0.0        
!
!
crypto ipsec transform-set TRANSFORM-SET esp-aes esp-sha-hmac 
 mode transport
!
crypto ipsec profile PROTECT-GRE
 set transform-set TRANSFORM-SET 
!
interface FastEthernet0/0
 ip address 1.1.14.1 255.255.255.0
!
interface FastEthernet0/1
 ip address 10.10.1.1 255.255.255.0
!
ip route 0.0.0.0 0.0.0.0 1.1.14.4
!

Site-2 Router R2:

hostname R2
!
ip cef
!
crypto isakmp policy 10
 encr aes
 authentication pre-share
 group 2
crypto isakmp key DmVpNpR3$h@r3dK3Y address 0.0.0.0        
!
crypto ipsec transform-set TRANSFORM-SET esp-aes esp-sha-hmac 
 mode transport
!
crypto ipsec profile PROTECT-GRE
 set transform-set TRANSFORM-SET 
!
interface FastEthernet0/0
 ip address 1.1.24.2 255.255.255.0
!
interface FastEthernet0/1
 ip address 10.10.2.2 255.255.255.0
!
ip route 0.0.0.0 0.0.0.0 1.1.24.4
!

Site-3 Router R3: 

hostname R3
!
ip cef
!
crypto isakmp policy 10
 encr aes
 authentication pre-share
 group 2
crypto isakmp key DmVpNpR3$h@r3dK3Y address 0.0.0.0        
!
!
crypto ipsec transform-set TRANSFORM-SET esp-aes esp-sha-hmac 
 mode transport
!
crypto ipsec profile PROTECT-GRE
 set transform-set TRANSFORM-SET 
!
interface FastEthernet0/0
 ip address 1.1.34.3 255.255.255.0
!
interface FastEthernet0/1
 ip address 10.10.3.3 255.255.255.0
!
ip route 0.0.0.0 0.0.0.0 1.1.34.4
!

Internet Router R4:

hostname R4
!
interface FastEthernet0/0
 ip address 1.1.14.4 255.255.255.0
!
interface FastEthernet0/1
 ip address 1.1.24.4 255.255.255.0
!
interface FastEthernet1/0
 ip address 1.1.34.4 255.255.255.0
!

DMVPN NBMA Network Behavior

DMVPN creates Non Broadcast Multi Access (NBMA) networks. By default, NBMA network do not support multicast traffic and multicast traffic is required to enable dynamic routing protocols.

“ip nhrp map multicast dynamic“ command is used under hub router tunnel interface to enable support of multicast traffic. This allows each spoke to register as a receiver of multicast traffic, causing the hub to replicate and forward multicast traffic to the spoke routers.

“ip nhrp map multicast <hub nbma ip>” command is used under spoke routers tunnel interface. It ensures multicast traffic is sent only from spokes to the hub and not from spoke to spoke.

With this set up, routing adjacencies are only formed between hub and spokes. Spokes do not form routing adjacencies with each other.

ip nhrp network-id

The NHRP network ID is used to define the NHRP domain for an NHRP interface and differentiate between multiple NHRP domains or networks, when two or more NHRP domains (GRE tunnel interfaces) are available on the same NHRP router. The NHRP network ID is used to help keep two NHRP networks (clouds) separate from each other when both are configured on the same router. NHRP network IDs are locally significant and can be different.

DMVPN Phase 1 configuration with EIGRP

----------
R1 - Hub:
----------

Since all spoke routers are configured with tunnel mode GRE (p2p GRE), they can send traffic via Hub only. So spoke routers do not require specific routes of each other. Hub router would advertise a single EIGRP summary route to all spoke routers. Basically Hub router is telling spokes if you want to reach any specific subnet from this summary route, send that traffic to me, I will forward it to actual destination spoke site.

interface Tunnel0
 bandwidth 4096
 ip address 192.168.1.1 255.255.255.0
 no ip redirects
 ip mtu 1400
 ip nhrp authentication NhRp@UtH
 ip nhrp map multicast dynamic
 ip nhrp network-id 100
 ip summary-address eigrp 100 10.10.0.0 255.255.0.0
 ip tcp adjust-mss 1360
 tunnel source FastEthernet0/0
 tunnel mode gre multipoint
 tunnel protection ipsec profile PROTECT-GRE
!
router eigrp 100
 network 10.10.1.1 0.0.0.0
 network 192.168.1.1 0.0.0.0

------------
R2 - Spoke: 
------------

interface Tunnel0
 bandwidth 4096
 ip address 192.168.1.2 255.255.255.0
 ip mtu 1400
 ip nhrp authentication NhRp@UtH
 ip nhrp map multicast 1.1.14.1
 ip nhrp map 192.168.1.1 1.1.14.1
 ip nhrp network-id 100
 ip nhrp nhs 192.168.1.1
 ip tcp adjust-mss 1360
 tunnel source FastEthernet0/0
 tunnel destination 1.1.14.1
 tunnel protection ipsec profile PROTECT-GRE
!
router eigrp 100
 network 10.10.2.2 0.0.0.0
 network 192.168.1.2 0.0.0.0

-----------
R3 - Spoke:
-----------

interface Tunnel0
 bandwidth 4096
 ip address 192.168.1.3 255.255.255.0
 ip mtu 1400
 ip nhrp authentication NhRp@UtH
 ip nhrp map multicast 1.1.14.1
 ip nhrp map 192.168.1.1 1.1.14.1
 ip nhrp network-id 100
 ip nhrp nhs 192.168.1.1
 ip tcp adjust-mss 1360
 tunnel source FastEthernet0/0
 tunnel destination 1.1.14.1
 tunnel protection ipsec profile PROTECT-GRE
!
router eigrp 100
 network 10.10.3.3 0.0.0.0
 network 192.168.1.3 0.0.0.0

Verification:

- Tunnel mode is mGRE on Hub Router.
- Tunnel mode is GRE (Point-to-Point GRE) on Spoke Routers.
 
 R1:
 
 R1#sh int t0
 Tunnel0 is up, line protocol is up 
   Hardware is Tunnel
   Internet address is 192.168.1.1/24
   MTU 17874 bytes, BW 4096 Kbit/sec, DLY 50000 usec, 
      reliability 255/255, txload 1/255, rxload 1/255
   Encapsulation TUNNEL, loopback not set
   Keepalive not set
   Tunnel source 1.1.14.1 (FastEthernet0/0)
    Tunnel Subblocks:
       src-track:
          Tunnel0 source tracking subblock associated with FastEthernet0/0
           Set of tunnels with source FastEthernet0/0, 1 member (includes iterators), on interface <OK>
   Tunnel protocol/transport multi-GRE/IP
     Key disabled, sequencing disabled
     Checksumming of packets disabled
   Tunnel TTL 255, Fast tunneling enabled
   Tunnel transport MTU 1434 bytes
   Tunnel transmit bandwidth 8000 (kbps)
   Tunnel receive bandwidth 8000 (kbps)
   Tunnel protection via IPSec (profile "PROTECT-GRE")
  <snip>
 
 R2:
 
 R2#sh int t0
 Tunnel0 is up, line protocol is up 
   Hardware is Tunnel
   Internet address is 192.168.1.2/24
   MTU 17874 bytes, BW 4096 Kbit/sec, DLY 50000 usec, 
      reliability 255/255, txload 1/255, rxload 1/255
   Encapsulation TUNNEL, loopback not set
   Keepalive not set
   Tunnel source 1.1.24.2 (FastEthernet0/0), destination 1.1.14.1
    Tunnel Subblocks:
       src-track:
          Tunnel0 source tracking subblock associated with FastEthernet0/0
           Set of tunnels with source FastEthernet0/0, 1 member (includes iterators), on interface <OK>
   Tunnel protocol/transport GRE/IP
     Key disabled, sequencing disabled
     Checksumming of packets disabled
   Tunnel TTL 255, Fast tunneling enabled
   Tunnel transport MTU 1434 bytes
   Tunnel transmit bandwidth 8000 (kbps)
   Tunnel receive bandwidth 8000 (kbps)
   Tunnel protection via IPSec (profile "PROTECT-GRE")
  <snip>
 
 R3:
 
 R3#sh int t0
 Tunnel0 is up, line protocol is up 
   Hardware is Tunnel
   Internet address is 192.168.1.3/24
   MTU 17874 bytes, BW 4096 Kbit/sec, DLY 50000 usec, 
      reliability 255/255, txload 1/255, rxload 1/255
   Encapsulation TUNNEL, loopback not set
   Keepalive not set
   Tunnel source 1.1.34.3 (FastEthernet0/0), destination 1.1.14.1
    Tunnel Subblocks:
       src-track:
          Tunnel0 source tracking subblock associated with FastEthernet0/0
           Set of tunnels with source FastEthernet0/0, 1 member (includes iterators), on interface <OK>
   Tunnel protocol/transport GRE/IP
     Key disabled, sequencing disabled
     Checksumming of packets disabled
   Tunnel TTL 255, Fast tunneling enabled
   Tunnel transport MTU 1434 bytes
   Tunnel transmit bandwidth 8000 (kbps)
   Tunnel receive bandwidth 8000 (kbps)
   Tunnel protection via IPSec (profile "PROTECT-GRE")
  <snip>
 
 
 - Routing adjacencies are Hub to Spokes only
 
 R1#show ip eigrp neighbors 
 EIGRP-IPv4 Neighbors for AS(100)
 H   Address                 Interface              Hold Uptime   SRTT   RTO  Q  Seq
                                                    (sec)         (ms)       Cnt Num
 1   192.168.1.3             Tu0                      11 00:19:56  191  1146  0  16
 0   192.168.1.2             Tu0                      14 00:19:56  178  1068  0  16
 
 R2#show ip eigrp neighbors
 EIGRP-IPv4 Neighbors for AS(100)
 H   Address                 Interface              Hold Uptime   SRTT   RTO  Q  Seq
                                                    (sec)         (ms)       Cnt Num
 0   192.168.1.1             Tu0                      11 00:20:37  779  4674  0  10
 
 R3#show ip eigrp neighbors
 EIGRP-IPv4 Neighbors for AS(100)
 H   Address                 Interface              Hold Uptime   SRTT   RTO  Q  Seq
                                                    (sec)         (ms)       Cnt Num
 0   192.168.1.1             Tu0                      14 00:20:39  183  1098  0  11 
 
 - Routing Table
 
 R1#show ip route eigrp | beg Gate
 Gateway of last resort is 1.1.14.4 to network 0.0.0.0
 
       10.0.0.0/8 is variably subnetted, 5 subnets, 3 masks
 D        10.10.0.0/16 is a summary, 00:14:48, Null0
 D        10.10.2.0/24 [90/1907456] via 192.168.1.2, 00:22:02, Tunnel0
 D        10.10.3.0/24 [90/1907456] via 192.168.1.3, 00:22:04, Tunnel0
 
 R2#show ip route eigrp | beg Gate
 Gateway of last resort is 1.1.24.4 to network 0.0.0.0
 
       10.0.0.0/8 is variably subnetted, 3 subnets, 3 masks
 D        10.10.0.0/16 [90/1907456] via 192.168.1.1, 00:15:06, Tunnel0
 
 R3#show ip route eigrp | beg Gate
 Gateway of last resort is 1.1.34.4 to network 0.0.0.0
 
       10.0.0.0/8 is variably subnetted, 3 subnets, 3 masks
 D        10.10.0.0/16 [90/1907456] via 192.168.1.1, 00:15:17, Tunnel0
 
 
 - Spoke (R2) to Spoke (R3) traffic traverse via Hub
 
 R2#ping 10.10.3.3 so 10.10.2.2
 Type escape sequence to abort.
 Sending 5, 100-byte ICMP Echos to 10.10.3.3, timeout is 2 seconds:
 Packet sent with a source address of 10.10.2.2 
 !!!!!
 Success rate is 100 percent (5/5), round-trip min/avg/max = 192/199/212 ms
 
 R2#trace 10.10.3.3 so 10.10.2.2
 Type escape sequence to abort.
 Tracing the route to 10.10.3.3
 VRF info: (vrf in name/id, vrf out name/id)
   1 192.168.1.1 144 msec 140 msec 136 msec   << Hub R1 Tunnel IP    
   2 192.168.1.3 204 msec *  196 msec         << Spoke R3 Tunnel IP

- DMVPN status on Hub
 
 R1#sh dmvpn
 Legend: Attrb --> S - Static, D - Dynamic, I - Incomplete
         N - NATed, L - Local, X - No Socket
         # Ent --> Number of NHRP entries with same NBMA peer
         NHS Status: E --> Expecting Replies, R --> Responding, W --> Waiting
         UpDn Time --> Up or Down Time for a Tunnel
 ======================================================================
 Interface: Tunnel0, IPv4 NHRP Details 
 Type:Hub, NHRP Peers:2, 
 
  # Ent  Peer NBMA Addr Peer Tunnel Add State  UpDn Tm Attrb
  ----- --------------- --------------- ----- -------- -----
      1 1.1.24.2            192.168.1.2    UP 01:21:07     D
      1 1.1.34.3            192.168.1.3    UP 01:21:11     D
 
R1#sh ip nhrp 
192.168.1.2/32 via 192.168.1.2
   Tunnel0 created 01:50:50, expire 01:29:09
   Type: dynamic, Flags: unique registered used 
   NBMA address: 1.1.24.2 
192.168.1.3/32 via 192.168.1.3
   Tunnel0 created 01:50:54, expire 01:29:05
   Type: dynamic, Flags: unique registered used 
   NBMA address: 1.1.34.3 

 - DMVPN status on Spoke Routers
 
 R2#sh dmvpn
 Legend: Attrb --> S - Static, D - Dynamic, I - Incomplete
         N - NATed, L - Local, X - No Socket
         # Ent --> Number of NHRP entries with same NBMA peer
         NHS Status: E --> Expecting Replies, R --> Responding, W --> Waiting
         UpDn Time --> Up or Down Time for a Tunnel
 =====================================================================
 Interface: Tunnel0, IPv4 NHRP Details 
 Type:Spoke, NHRP Peers:1, 
 
  # Ent  Peer NBMA Addr Peer Tunnel Add State  UpDn Tm Attrb
  ----- --------------- --------------- ----- -------- -----
      1 1.1.14.1            192.168.1.1    UP 01:22:47     S
 
R2#sh ip nhrp
192.168.1.1/32 via 192.168.1.1
   Tunnel0 created 01:53:57, never expire 
   Type: static, Flags: 
   NBMA address: 1.1.14.1 
 R3#sh dmvpn
 Legend: Attrb --> S - Static, D - Dynamic, I - Incomplete
         N - NATed, L - Local, X - No Socket
         # Ent --> Number of NHRP entries with same NBMA peer
         NHS Status: E --> Expecting Replies, R --> Responding, W --> Waiting
         UpDn Time --> Up or Down Time for a Tunnel
 ====================================================================
 Interface: Tunnel0, IPv4 NHRP Details 
 Type:Spoke, NHRP Peers:1, 
 
  # Ent  Peer NBMA Addr Peer Tunnel Add State  UpDn Tm Attrb
  ----- --------------- --------------- ----- -------- -----
      1 1.1.14.1            192.168.1.1    UP 01:23:09     S


R3#sh ip nhrp
192.168.1.1/32 via 192.168.1.1
   Tunnel0 created 01:54:39, never expire 
   Type: static, Flags: 
   NBMA address: 1.1.14.1

DMVPN Phase 1 configuration with OSPF

- Hub router tunnel would be OSPF network type point-to-multipoint
- Spoke routers tunnel would be OSPF network type point-to-point
- OSPF hello timers must match on tunnel interface on Hub and Spokes
- Route summarization is not feasible in single OSPF area

R1:

interface Tunnel0
 bandwidth 4096
 ip address 192.168.1.1 255.255.255.0
 no ip redirects
 ip mtu 1400
 ip nhrp authentication NhRp@UtH
 ip nhrp map multicast dynamic
 ip nhrp network-id 100
 ip tcp adjust-mss 1360
 ip ospf network point-to-multipoint
 ip ospf hello-interval 10
 tunnel source FastEthernet0/0
 tunnel mode gre multipoint
 tunnel protection ipsec profile PROTECT-GRE
!
router ospf 1
 network 10.10.1.1 0.0.0.0 area 0
 network 192.168.1.1 0.0.0.0 area 0

R2:

interface Tunnel0
 bandwidth 4096
 ip address 192.168.1.2 255.255.255.0
 ip mtu 1400
 ip nhrp authentication NhRp@UtH
 ip nhrp map multicast 1.1.14.1
 ip nhrp map 192.168.1.1 1.1.14.1
 ip nhrp network-id 100
 ip nhrp nhs 192.168.1.1
 ip tcp adjust-mss 1360
 tunnel source FastEthernet0/0
 tunnel destination 1.1.14.1
 tunnel protection ipsec profile PROTECT-GRE
!
router ospf 1
 network 10.10.2.2 0.0.0.0 area 0
 network 192.168.1.2 0.0.0.0 area 0

R3:

interface Tunnel0
 bandwidth 4096
 ip address 192.168.1.3 255.255.255.0
 ip mtu 1400
 ip nhrp authentication NhRp@UtH
 ip nhrp map multicast 1.1.14.1
 ip nhrp map 192.168.1.1 1.1.14.1
 ip nhrp network-id 100
 ip nhrp nhs 192.168.1.1
 ip tcp adjust-mss 1360
 tunnel source FastEthernet0/0
 tunnel destination 1.1.14.1
 tunnel protection ipsec profile PROTECT-GRE
!
router ospf 1
 network 10.10.3.3 0.0.0.0 area 0
 network 192.168.1.3 0.0.0.0 area 0

Verification

R1:

R1#show ip ospf int t0
Tunnel0 is up, line protocol is up 
  Internet Address 192.168.1.1/24, Area 0, Attached via Network Statement
  Process ID 1, Router ID 192.168.1.1, Network Type POINT_TO_MULTIPOINT, Cost: 24
  Topology-MTID    Cost    Disabled    Shutdown      Topology Name
        0           24        no          no            Base
  Transmit Delay is 1 sec, State POINT_TO_MULTIPOINT
  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
    oob-resync timeout 40
    Hello due in 00:00:05
  Supports Link-local Signaling (LLS)
  Cisco NSF helper support enabled
  IETF NSF helper support enabled
  Index 2/2, flood queue length 0
  Next 0x0(0)/0x0(0)
  Last flood scan length is 1, maximum is 1
  Last flood scan time is 4 msec, maximum is 4 msec
  Neighbor Count is 2, Adjacent neighbor count is 2 
    Adjacent with neighbor 192.168.1.3
    Adjacent with neighbor 192.168.1.2
  Suppress hello for 0 neighbor(s)

R1#show ip ospf ne

Neighbor ID     Pri   State           Dead Time   Address         Interface
192.168.1.3       0   FULL/  -        00:00:33    192.168.1.3     Tunnel0
192.168.1.2       0   FULL/  -        00:00:34    192.168.1.2     Tunnel0

R1#show ip route ospf | beg Gate
Gateway of last resort is 1.1.14.4 to network 0.0.0.0

      10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
O        10.10.2.0/24 [110/25] via 192.168.1.2, 00:04:05, Tunnel0
O        10.10.3.0/24 [110/25] via 192.168.1.3, 00:03:45, Tunnel0

R2:

R2#show ip ospf int t0
Tunnel0 is up, line protocol is up 
  Internet Address 192.168.1.2/24, Area 0, Attached via Network Statement
  Process ID 1, Router ID 192.168.1.2, Network Type POINT_TO_POINT, Cost: 24
  Topology-MTID    Cost    Disabled    Shutdown      Topology Name
        0           24        no          no            Base
  Transmit Delay is 1 sec, State POINT_TO_POINT
  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
    oob-resync timeout 40
    Hello due in 00:00:08
  Supports Link-local Signaling (LLS)
  Cisco NSF helper support enabled
  IETF NSF helper support enabled
  Index 2/2, flood queue length 0
  Next 0x0(0)/0x0(0)
  Last flood scan length is 1, maximum is 1
  Last flood scan time is 4 msec, maximum is 4 msec
  Neighbor Count is 1, Adjacent neighbor count is 1 
    Adjacent with neighbor 192.168.1.1
  Suppress hello for 0 neighbor(s)

R2#show ip ospf ne

Neighbor ID     Pri   State           Dead Time   Address         Interface
192.168.1.1       0   FULL/  -        00:00:31    192.168.1.1     Tunnel0

R2#show ip route ospf | beg Gate
Gateway of last resort is 1.1.24.4 to network 0.0.0.0

      10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
O        10.10.1.0/24 [110/25] via 192.168.1.1, 00:05:12, Tunnel0
O        10.10.3.0/24 [110/49] via 192.168.1.1, 00:04:35, Tunnel0
      192.168.1.0/24 is variably subnetted, 3 subnets, 2 masks
O        192.168.1.1/32 [110/24] via 192.168.1.1, 00:05:12, Tunnel0


R3:

R3#show ip ospf int t0
Tunnel0 is up, line protocol is up 
  Internet Address 192.168.1.3/24, Area 0, Attached via Network Statement
  Process ID 1, Router ID 192.168.1.3, Network Type POINT_TO_POINT, Cost: 24
  Topology-MTID    Cost    Disabled    Shutdown      Topology Name
        0           24        no          no            Base
  Transmit Delay is 1 sec, State POINT_TO_POINT
  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
    oob-resync timeout 40
    Hello due in 00:00:02
  Supports Link-local Signaling (LLS)
  Cisco NSF helper support enabled
  IETF NSF helper support enabled
  Index 2/2, flood queue length 0
  Next 0x0(0)/0x0(0)
  Last flood scan length is 1, maximum is 1
  Last flood scan time is 4 msec, maximum is 4 msec
  Neighbor Count is 1, Adjacent neighbor count is 1 
    Adjacent with neighbor 192.168.1.1
  Suppress hello for 0 neighbor(s)

R3#show ip ospf ne

Neighbor ID     Pri   State           Dead Time   Address         Interface
192.168.1.1       0   FULL/  -        00:00:31    192.168.1.1     Tunnel0

R3#show ip route ospf | beg Gate
Gateway of last resort is 1.1.34.4 to network 0.0.0.0

      10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
O        10.10.1.0/24 [110/25] via 192.168.1.1, 00:05:40, Tunnel0
O        10.10.2.0/24 [110/49] via 192.168.1.1, 00:05:40, Tunnel0
      192.168.1.0/24 is variably subnetted, 3 subnets, 2 masks
O        192.168.1.1/32 [110/24] via 192.168.1.1, 00:05:40, Tunnel0


Spoke to Spoke traffic:

R2#ping 10.10.3.3 so 10.10.2.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.10.3.3, timeout is 2 seconds:
Packet sent with a source address of 10.10.2.2 
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 196/201/208 ms

R2#trace 10.10.3.3 so 10.10.2.2
Type escape sequence to abort.
Tracing the route to 10.10.3.3
VRF info: (vrf in name/id, vrf out name/id)
  1 192.168.1.1 152 msec 120 msec 164 msec   << Hub Tunnel IP
  2 192.168.1.3 236 msec *  220 msec         << Spoke-3 Tunnel IP

DMVPN Phase 1 configuration with BGP

- "bgp listen range ....." command can be used to define a range of IP address of BGP neighbors on hub router
- "bgp listen limit xx" command can be used to set the limit of dynamic BGP neighbors
- Hub router would act as BGP Route-reflector server
- Spoke routers would be BGP route-reflector clients
- As spokes would communicate via hub only, it is inefficient to advertise all specific prefixes to spoke BGP peers
- Hub Router would advertise summary route to spokes

R1:

interface Tunnel0
 bandwidth 4096
 ip address 192.168.1.1 255.255.255.0
 no ip redirects
 ip mtu 1400
 ip nhrp authentication NhRp@UtH
 ip nhrp network-id 100
 ip tcp adjust-mss 1360
 tunnel source FastEthernet0/0
 tunnel mode gre multipoint
 tunnel protection ipsec profile PROTECT-GRE
!
router bgp 65001
 bgp router-id 192.168.1.1
 bgp log-neighbor-changes
 bgp listen range 192.168.1.0/24 peer-group DMVPN-SPOKES
 bgp listen limit 50
 network 10.10.1.0 mask 255.255.255.0
 aggregate-address 10.10.0.0 255.255.0.0 summary-only
 neighbor DMVPN-SPOKES peer-group
 neighbor DMVPN-SPOKES remote-as 65001
 neighbor DMVPN-SPOKES route-reflector-client

R2: 

interface Tunnel0
 bandwidth 4096
 ip address 192.168.1.2 255.255.255.0
 ip mtu 1400
 ip nhrp authentication NhRp@UtH
 ip nhrp map 192.168.1.1 1.1.14.1
 ip nhrp network-id 100
 ip nhrp nhs 192.168.1.1
 ip tcp adjust-mss 1360
 tunnel source FastEthernet0/0
 tunnel destination 1.1.14.1
 tunnel protection ipsec profile PROTECT-GRE
!
router bgp 65001
 bgp router-id 192.168.1.2
 bgp log-neighbor-changes
 network 10.10.2.0 mask 255.255.255.0
 neighbor 192.168.1.1 remote-as 65001

R3:

interface Tunnel0
 bandwidth 4096
 ip address 192.168.1.3 255.255.255.0
 ip mtu 1400
 ip nhrp authentication NhRp@UtH
 ip nhrp map 192.168.1.1 1.1.14.1
 ip nhrp network-id 100
 ip nhrp nhs 192.168.1.1
 ip tcp adjust-mss 1360
 tunnel source FastEthernet0/0
 tunnel destination 1.1.14.1
 tunnel protection ipsec profile PROTECT-GRE
!
router bgp 65001
 bgp router-id 192.168.1.3
 bgp log-neighbor-changes
 network 10.10.3.0 mask 255.255.255.0
 neighbor 192.168.1.1 remote-as 65001

Verification

R1:

R1#show ip bgp summary 
BGP router identifier 192.168.1.1, local AS number 65001
BGP table version is 8, main routing table version 8
4 network entries using 592 bytes of memory
4 path entries using 256 bytes of memory
3/3 BGP path/bestpath attribute entries using 408 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
BGP using 1256 total bytes of memory
BGP activity 4/0 prefixes, 4/0 paths, scan interval 60 secs

Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
*192.168.1.2    4        65001      38      40        8    0    0 00:30:25        1
*192.168.1.3    4        65001      37      39        8    0    0 00:30:09        1
* Dynamically created based on a listen range command
Dynamically created neighbors: 2, Subnet ranges: 1

BGP peergroup DMVPN-SPOKES listen range group members: 
  192.168.1.0/24 

Total dynamically created neighbors: 2/(50 max), Subnet ranges: 1

R1#show ip bgp
BGP table version is 8, local router ID is 192.168.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, 
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, 
              x best-external, a additional-path, c RIB-compressed, 
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>  10.10.0.0/16     0.0.0.0                            32768 i
 s>  10.10.1.0/24     0.0.0.0                  0         32768 i
 s>i 10.10.2.0/24     192.168.1.2              0    100      0 i
 s>i 10.10.3.0/24     192.168.1.3              0    100      0 i

R1#show ip route bgp | beg Gate
Gateway of last resort is 1.1.14.4 to network 0.0.0.0

      10.0.0.0/8 is variably subnetted, 5 subnets, 3 masks
B        10.10.0.0/16 [200/0] via 0.0.0.0, 00:30:49, Null0
B        10.10.2.0/24 [200/0] via 192.168.1.2, 00:30:49
B        10.10.3.0/24 [200/0] via 192.168.1.3, 00:29:46

R2:

R2#show ip bgp sum
BGP router identifier 192.168.1.2, local AS number 65001
BGP table version is 5, main routing table version 5
2 network entries using 296 bytes of memory
2 path entries using 128 bytes of memory
2/2 BGP path/bestpath attribute entries using 272 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
BGP using 696 total bytes of memory
BGP activity 3/1 prefixes, 3/1 paths, scan interval 60 secs

Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
192.168.1.1     4        65001      41      40        5    0    0 00:31:43        1

R2#show ip bgp
BGP table version is 5, local router ID is 192.168.1.2
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, 
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, 
              x best-external, a additional-path, c RIB-compressed, 
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>i 10.10.0.0/16     192.168.1.1              0    100      0 i
 *>  10.10.2.0/24     0.0.0.0                  0         32768 i

R2#show ip route bgp | beg Gate 
Gateway of last resort is 1.1.24.4 to network 0.0.0.0

      10.0.0.0/8 is variably subnetted, 3 subnets, 3 masks
B        10.10.0.0/16 [200/0] via 192.168.1.1, 00:31:53

R3:

R3#show ip bgp sum
BGP router identifier 192.168.1.3, local AS number 65001
BGP table version is 3, main routing table version 3
2 network entries using 296 bytes of memory
2 path entries using 128 bytes of memory
2/2 BGP path/bestpath attribute entries using 272 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
BGP using 696 total bytes of memory
BGP activity 2/0 prefixes, 2/0 paths, scan interval 60 secs

Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
192.168.1.1     4        65001      41      39        3    0    0 00:32:08        1

R3#show ip bgp
BGP table version is 3, local router ID is 192.168.1.3
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, 
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, 
              x best-external, a additional-path, c RIB-compressed, 
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>i 10.10.0.0/16     192.168.1.1              0    100      0 i
 *>  10.10.3.0/24     0.0.0.0                  0         32768 i

R3#show ip route bgp | beg Gate
Gateway of last resort is 1.1.34.4 to network 0.0.0.0

      10.0.0.0/8 is variably subnetted, 3 subnets, 3 masks
B        10.10.0.0/16 [200/0] via 192.168.1.1, 00:31:29

Spoke-to-Spoke traffic:

R2#ping 10.10.3.3 so 10.10.2.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.10.3.3, timeout is 2 seconds:
Packet sent with a source address of 10.10.2.2 
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 180/192/204 ms

R2#trace 10.10.3.3 so 10.10.2.2
Type escape sequence to abort.
Tracing the route to 10.10.3.3
VRF info: (vrf in name/id, vrf out name/id)
  1 192.168.1.1 140 msec 176 msec 140 msec   << Hub Tunnel IP
  2 192.168.1.3 224 msec *  220 msec         << Spoke-3 Tunnel IP

As we have seen that spoke-to-spoke traffic always traverse via hub in phase 1 design. In a large network, It increases overhead on hub router. Also spokes has to use sub-optimal routing path for traffic between spoke sites. The shortcomings of DMVPN phase 1 are addressed in Phase 2 design, which we will discuss in next blog.

BGP Outbound Route Filtering – ORF

April 8, 2016BGP, Cisco, Service ProviderBGP, ORF, Outbound Router FilteringAmolak

When a customer connects a CE router to provider PE router for BGP peering, there are limited options for what routes a CE can receive from PE via BGP. Usually Service provider give the customer option of sending Full BGP table, just a default route, or some specific prefix such as default route + service provider’s locally originated prefix. Normally service provider do not want to implement complex outbound route filter policy for the customer. And customer implement a inbound route filter policy to receive prefix whatever they required.

From administrative point of view service provider is happy as they don’t have to worry about the change request coming from customer to add or remove the prefix in provider to customer advertisements.

Similarly, customer don’t have to submit a change request to service provider and can modify inbound filter policy as per their requirements.

But from a resources usage point of view this is not a optimal design. Provider router is still sending full bgp table (around 500k prefix) and customer router also process all of the BGP updates and ultimately just wanted to accept a few prefixes (sometime 1-2%) and deny all others.

Here, BGP Outbound Route Filtering capability plays a significant role to optimize this design without increasing the administrative overhead for service provider to make frequent changes for filtering prefix advertisements to the customer.

With BGP ORF capability, CE router tells dynamically PE Routers what outbound filter PE should use to advertise prefix to the CE.

Let’s configure this feature and see how it works. We will use following network topology for this discussion.

Here is the initial BGP configuration and status on both routers:

PE Router

- BGP Peering is UP between PE and CE Router
- PE is advertising full bgp table to CE

R2#sh run | s bgp
router bgp 200
 bgp log-neighbor-changes
 network 0.0.0.0
 network 2.2.1.0 mask 255.255.255.0
 network 2.2.2.0 mask 255.255.255.0
 network 2.2.3.0 mask 255.255.255.0
 network 2.2.4.0 mask 255.255.255.0
 network 2.2.5.0 mask 255.255.255.0
 neighbor 1.1.1.1 remote-as 100

R2#sh ip bgp sum | b Nei
Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
1.1.1.1         4          100       5       6        7    0    0 00:01:39        0

R2#sh ip bgp
BGP table version is 7, local router ID is 2.2.5.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,
              x best-external, a additional-path, c RIB-compressed,
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>  0.0.0.0          0.0.0.0                  0         32768 i
 *>  2.2.1.0/24       0.0.0.0                  0         32768 i
 *>  2.2.2.0/24       0.0.0.0                  0         32768 i
 *>  2.2.3.0/24       0.0.0.0                  0         32768 i
 *>  2.2.4.0/24       0.0.0.0                  0         32768 i
 *>  2.2.5.0/24       0.0.0.0                  0         32768 i

R2#sh ip bgp neighbors 1.1.1.1 advertised-routes
BGP table version is 7, local router ID is 2.2.5.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,
              x best-external, a additional-path, c RIB-compressed,
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>  0.0.0.0          0.0.0.0                  0         32768 i
 *>  2.2.1.0/24       0.0.0.0                  0         32768 i
 *>  2.2.2.0/24       0.0.0.0                  0         32768 i
 *>  2.2.3.0/24       0.0.0.0                  0         32768 i
 *>  2.2.4.0/24       0.0.0.0                  0         32768 i
 *>  2.2.5.0/24       0.0.0.0                  0         32768 i

Total number of prefixes 6

CE Router

- BGP Peering is UP between CE and PE Router
- CE is receiving full bgp table from PE

R1#sh run | s bgp
router bgp 100
 bgp log-neighbor-changes
 neighbor 1.1.1.2 remote-as 200

R1#sh ip bgp sum | b Nei
Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
1.1.1.2         4          200      12      12       19    0    0 00:07:35        6

R1#sh ip bgp
BGP table version is 19, local router ID is 1.1.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,
              x best-external, a additional-path, c RIB-compressed,
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>  0.0.0.0          1.1.1.2                  0             0 200 i
 *>  2.2.1.0/24       1.1.1.2                  0             0 200 i
 *>  2.2.2.0/24       1.1.1.2                  0             0 200 i
 *>  2.2.3.0/24       1.1.1.2                  0             0 200 i
 *>  2.2.4.0/24       1.1.1.2                  0             0 200 i
 *>  2.2.5.0/24       1.1.1.2                  0             0 200 i

Let’s first apply inbound filter on CE Router. CE want to accept below prefix only:

Default route + 2 specific prefix
0.0.0.0/0
2.2.1.0/24
2.2.2.0/24

R1#
R1#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
R1(config)#ip prefix-list FILTER permit 0.0.0.0/0
R1(config)#ip prefix-list FILTER permit 2.2.1.0/24
R1(config)#ip prefix-list FILTER permit 2.2.2.0/24
R1(config)#
R1(config)#router bgp 100
R1(config-router)# neighbor 1.1.1.2 prefix-list FILTER in
R1(config-router)#
R1(config-router)#end
R1#
*Apr  8 12:09:58.667: %SYS-5-CONFIG_I: Configured from console by console
R1#clear ip bgp * soft
R1#sh ip bgp
BGP table version is 22, local router ID is 1.1.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,
              x best-external, a additional-path, c RIB-compressed,
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>  0.0.0.0          1.1.1.2                  0             0 200 i
 *>  2.2.1.0/24       1.1.1.2                  0             0 200 i
 *>  2.2.2.0/24       1.1.1.2                  0             0 200 i

it appears our requirement is fulfilled but there is something not optimal behind the scene. Let’s debug the BGP advertisements.

PE is still advertising full BGP table to CE.

R2#sh ip bgp neighbors 1.1.1.1 advertised-routes
BGP table version is 7, local router ID is 2.2.5.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,
              x best-external, a additional-path, c RIB-compressed,
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>  0.0.0.0          0.0.0.0                  0         32768 i
 *>  2.2.1.0/24       0.0.0.0                  0         32768 i
 *>  2.2.2.0/24       0.0.0.0                  0         32768 i
 *>  2.2.3.0/24       0.0.0.0                  0         32768 i
 *>  2.2.4.0/24       0.0.0.0                  0         32768 i
 *>  2.2.5.0/24       0.0.0.0                  0         32768 i

Total number of prefixes 6

We can see before accepting the required 3 prefixes in BGP table, CE router has processed all received prefixes from PE and denied the prefixes which are not permitted in the inbound prefix-list applied for neighbor 1.1.1.2 on CE router. Just imagine the resources usage if it was the actual full bgp table of 500K prefixes.

R1#debug ip bgp updates
BGP updates debugging is on for address family: IPv4 Unicast
R1#
R1#clear ip bgp 1.1.1.2
R1#
*Apr  8 12:15:10.551: BGP(0): no valid path for 0.0.0.0/0
*Apr  8 12:15:10.555: BGP(0): no valid path for 2.2.1.0/24
*Apr  8 12:15:10.559: BGP(0): no valid path for 2.2.2.0/24
*Apr  8 12:15:10.567: %BGP-5-ADJCHANGE: neighbor 1.1.1.2 Down User reset
*Apr  8 12:15:10.571: %BGP_SESSION-5-ADJCHANGE: neighbor 1.1.1.2 IPv4 Unicast topology base removed from session  User reset
*Apr  8 12:15:10.575: BGP: topo global:IPv4 Unicast:base Remove_fwdroute for 0.0.0.0/0
*Apr  8 12:15:10.583: BGP: topo global:IPv4 Unicast:base Remove_fwdroute for 2.2.1.0/24
*Apr  8 12:15:10.591: BGP: topo global:IPv4 Unicast:base Remove_fwdroute for 2.2.2.0/24
*Apr  8 12:15:10.883: %BGP-5-ADJCHANGE: neighbor 1.1.1.2 Up
*Apr  8 12:15:10.979: BGP(0): 1.1.1.2 rcvd UPDATE w/ attr: nexthop 1.1.1.2, origin i, metric 0, merged path 200, AS_PATH
*Apr  8 12:15:10.991: BGP(0): 1.1.1.2 rcvd 0.0.0.0/0
*Apr  8 12:15:10.995: BGP(0): 1.1.1.2 rcvd 2.2.1.0/24
*Apr  8 12:15:10.999: BGP(0): 1.1.1.2 rcvd 2.2.2.0/24
*Ap
R1#r  8 12:15:11.003: BGP(0): 1.1.1.2 rcvd 2.2.3.0/24 -- DENIED due to: distribute/prefix-list;
*Apr  8 12:15:11.007: BGP(0): 1.1.1.2 rcvd 2.2.4.0/24 -- DENIED due to: distribute/prefix-list;
*Apr  8 12:15:11.011: BGP(0): 1.1.1.2 rcvd 2.2.5.0/24 -- DENIED due to: distribute/prefix-list;
*Apr  8 12:15:11.015: BGP(0): Revise route installing 1 of 1 routes for 0.0.0.0/0 -> 1.1.1.2(global) to main IP table
*Apr  8 12:15:11.015: BGP(0): Revise route installing 1 of 1 routes for 2.2.1.0/24 -> 1.1.1.2(global) to main IP table
*Apr  8 12:15:11.019: BGP(0): Revise route installing 1 of 1 routes for 2.2.2.0/24 -> 1.1.1.2(global) to main IP table

R1#sh ip bgp
BGP table version is 34, local router ID is 1.1.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,
              x best-external, a additional-path, c RIB-compressed,
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>  0.0.0.0          1.1.1.2                  0             0 200 i
 *>  2.2.1.0/24       1.1.1.2                  0             0 200 i
 *>  2.2.2.0/24       1.1.1.2                  0             0 200 i

Let’s try BGP ORF feature now.

CE Router - R1

R1#
R1#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
R1(config)#ip prefix-list FILTER permit 0.0.0.0/0
R1(config)#ip prefix-list FILTER permit 2.2.1.0/24
R1(config)#ip prefix-list FILTER permit 2.2.2.0/24
R1(config)#
R1(config)#router bgp 100
R1(config-router)#neighbor 1.1.1.2 capability orf prefix-list send
R1(config-router)# neighbor 1.1.1.2 prefix-list FILTER in
R1(config-router)#end
*Apr  8 12:22:38.879: %BGP-5-ADJCHANGE: neighbor 1.1.1.2 Down Capability changed
*Apr  8 12:22:38.883: %BGP_SESSION-5-ADJCHANGE: neighbor 1.1.1.2 IPv4 Unicast topology base removed from session  Capability changed
*Apr  8 12:22:39.391: %BGP-5-ADJCHANGE: neighbor 1.1.1.2 Up


PE Router - R2

R2#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
R2(config)#router bgp 200
R2(config-router)#neighbor 1.1.1.1 capability orf prefix-list receive
R2(config-router)#
*Apr  8 12:26:25.267: %BGP-5-ADJCHANGE: neighbor 1.1.1.1 Down Capability changed
*Apr  8 12:26:25.271: %BGP_SESSION-5-ADJCHANGE: neighbor 1.1.1.1 IPv4 Unicast topology base removed from session  Capability changed
*Apr  8 12:26:25.955: %BGP-5-ADJCHANGE: neighbor 1.1.1.1 Up
R2(config-router)#
R2(config-router)#end
R2#

Verification:

CE Router (R1) has negotiated ORF capability with neighbor router (PE R2) and sent the prefix-list ORF to PE neighbor. 

R1#sh ip bgp neighbors 1.1.1.2

<snip>

 For address family: IPv4 Unicast
  Session: 1.1.1.2
  BGP table version 46, neighbor version 46/0
  Output queue size : 0
  Index 7, Advertise bit 0
  7 update-group member
  AF-dependant capabilities:
    Outbound Route Filter (ORF) type (128) Prefix-list:
      Send-mode: advertised
      Receive-mode: received
  Outbound Route Filter (ORF): sent;
  Incoming update prefix filter list is FILTER

<snip>

PE Router (R2) has negotiated ORF capability with neighbor router (CE R1) and received the prefix-list ORF from CE neighbor.

R2#sh ip bgp neighbors 1.1.1.1

<snip>

 For address family: IPv4 Unicast
  Session: 1.1.1.1
  BGP table version 7, neighbor version 7/0
  Output queue size : 0
  Index 7, Advertise bit 0
  7 update-group member
  AF-dependant capabilities:
    Outbound Route Filter (ORF) type (128) Prefix-list:
      Send-mode: received
      Receive-mode: advertised
  Outbound Route Filter (ORF): received (3 entries)

<snip> 


R2#sh ip bgp neighbors 1.1.1.1 received prefix-filter
Address family: IPv4 Unicast
ip prefix-list 1.1.1.1: 3 entries
   seq 5 permit 0.0.0.0/0
   seq 10 permit 2.2.1.0/24
   seq 15 permit 2.2.2.0/24
R2#

!! -- You can see there is no local prefix-list in running configuration of R2 --!!

R2#sh ip prefix-list
R2#

!! -- Now R2 is advertising only those prefixes to neighbor which are permitted in ORF prefix-list --!! 

R2#sh ip bgp neighbors 1.1.1.1 advertised-routes
BGP table version is 7, local router ID is 2.2.5.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,
              x best-external, a additional-path, c RIB-compressed,
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>  0.0.0.0          0.0.0.0                  0         32768 i
 *>  2.2.1.0/24       0.0.0.0                  0         32768 i
 *>  2.2.2.0/24       0.0.0.0                  0         32768 i

Total number of prefixes 3

Let's debug bgp updates on R1 to see what it is receiving.
It is receiving only required prefix from neighbor. There is no extra CPU resources used for processing unnecessary updates.

R1#debug ip bgp updates
BGP updates debugging is on for address family: IPv4 Unicast

R1#clear ip bgp 1.1.1.2
R1#
*Apr  8 13:10:36.119: BGP(0): no valid path for 0.0.0.0/0
*Apr  8 13:10:36.123: BGP(0): no valid path for 2.2.1.0/24
*Apr  8 13:10:36.123: BGP(0): no valid path for 2.2.2.0/24
*Apr  8 13:10:36.135: %BGP-5-ADJCHANGE: neighbor 1.1.1.2 Down User reset
*Apr  8 13:10:36.139: %BGP_SESSION-5-ADJCHANGE: neighbor 1.1.1.2 IPv4 Unicast topology base removed from session  User reset
*Apr  8 13:10:36.143: BGP: topo global:IPv4 Unicast:base Remove_fwdroute for 0.0.0.0/0
*Apr  8 13:10:36.147: BGP: topo global:IPv4 Unicast:base Remove_fwdroute for 2.2.1.0/24
*Apr  8 13:10:36.155: BGP: topo global:IPv4 Unicast:base Remove_fwdroute for 2.2.2.0/24
R1#
*Apr  8 13:10:37.291: %BGP-5-ADJCHANGE: neighbor 1.1.1.2 Up
*Apr  8 13:10:38.219: BGP(0): 1.1.1.2 rcvd UPDATE w/ attr: nexthop 1.1.1.2, origin i, metric 0, merged path 200, AS_PATH
*Apr  8 13:10:38.227: BGP(0): 1.1.1.2 rcvd 0.0.0.0/0
*Apr  8 13:10:38.231: BGP(0): 1.1.1.2 rcvd 2.2.1.0/24
*Apr  8 13:10:38.235: BGP(0): 1.1.1.2 rcvd 2.2.2.0/24
*Apr  8 13:10:38.239: BGP(0): Revise route installing 1 of 1 routes for 0.0.0.0/0 -> 1.1.1.2(global) to main IP table
*Apr  8 13:10:38.247: BGP(0): Revise route installing 1 of 1 routes for 2.2.1.0/24 -> 1.1.1.2(global) to main IP table
*Apr  8 13:10:38.247: BGP(0): Revise route installing 1 of 1 routes for 2.2.2.0/24 -> 1.1.1.2(global) to main IP table
R1#

In future, if CE want to receive one more prefix 2.2.3.0/24 from PE. CE just have to modify its prefix-list.

!!-- Existing prefix-list --!!
R1#sh ip prefix-list
ip prefix-list FILTER: 3 entries
   seq 5 permit 0.0.0.0/0
   seq 10 permit 2.2.1.0/24
   seq 15 permit 2.2.2.0/24
R1#
R1#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
R1(config)#ip prefix-list FILTER seq 20 permit 2.2.3.0/24
R1(config)#
R1(config)#end
R1#
*Apr  8 13:15:03.579: %SYS-5-CONFIG_I: Configured from console by console

!!-- New prefix-list --!!
R1#sh ip prefix-list
ip prefix-list FILTER: 4 entries
   seq 5 permit 0.0.0.0/0
   seq 10 permit 2.2.1.0/24
   seq 15 permit 2.2.2.0/24
   seq 20 permit 2.2.3.0/24
R1#

R1#clear ip bgp 1.1.1.2 in ?
  prefix-filter  Push out prefix-list ORF and do inbound soft reconfig
  <cr>
R1#clear ip bgp 1.1.1.2 in prefix-filter


R2 has the updated prefix-filter now.

R2#sh ip bgp neighbors 1.1.1.1 received prefix-filter
Address family: IPv4 Unicast
ip prefix-list 1.1.1.1: 4 entries
   seq 5 permit 0.0.0.0/0
   seq 10 permit 2.2.1.0/24
   seq 15 permit 2.2.2.0/24
   seq 20 permit 2.2.3.0/24

R2 advertised prefixes based on the updated prefix-filter

R2#sh ip bgp neighbors 1.1.1.1 advertised-routes
BGP table version is 7, local router ID is 2.2.5.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,
              x best-external, a additional-path, c RIB-compressed,
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>  0.0.0.0          0.0.0.0                  0         32768 i
 *>  2.2.1.0/24       0.0.0.0                  0         32768 i
 *>  2.2.2.0/24       0.0.0.0                  0         32768 i
 *>  2.2.3.0/24       0.0.0.0                  0         32768 i

Total number of prefixes 4

R1 has the required prefixes in its BGP table. 

R1#sh ip bgp
BGP table version is 59, local router ID is 1.1.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,
              x best-external, a additional-path, c RIB-compressed,
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>  0.0.0.0          1.1.1.2                  0             0 200 i
 *>  2.2.1.0/24       1.1.1.2                  0             0 200 i
 *>  2.2.2.0/24       1.1.1.2                  0             0 200 i
 *>  2.2.3.0/24       1.1.1.2                  0             0 200 i

BGP Default Route

March 24, 2016BGP, Cisco, Service ProviderBGP, Default RouteAmolak

We will discuss the different ways to advertise a default route in BGP. We will use following network topology for the same.

1. default-information originate

A default route can be injected into BGP with the command ‘default-information originate’. Following conditions must be fulfilled to use this method.

– A default route must be in the local routing table.
– The default route must be redistributed into the BGP
– Add ‘default-information originate’ under router bgp <ASN>

Here is the initial configuration and BGP status on all routers.

Let’s first try to add a static default route and redistribute it into BGP on R1.

R1#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
R1(config)#ip route 0.0.0.0 0.0.0.0 null0
R1(config)#router bgp 100
R1(config-router)#redistribute static
R1(config-router)#
R1(config-router)#do sh run | s bgp
router bgp 100
 bgp router-id 1.1.1.1
 bgp log-neighbor-changes
 network 1.1.1.0 mask 255.255.255.0
 redistribute static
 neighbor 12.12.12.2 remote-as 200
 neighbor 13.13.13.3 remote-as 300
 neighbor 14.14.14.4 remote-as 100
 neighbor 14.14.14.4 next-hop-self
R1(config-router)#do sh ip route 0.0.0.0
Routing entry for 0.0.0.0/0, supernet
  Known via "static", distance 1, metric 0 (connected), candidate default path
  Redistributing via bgp 100
  Routing Descriptor Blocks:
  * directly connected, via Null0
      Route metric is 0, traffic share count is 1
R1(config-router)#
R1(config-router)#do sh ip bgp
BGP table version is 10, local router ID is 1.1.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,
              x best-external, a additional-path, c RIB-compressed,
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>  1.1.1.0/24       0.0.0.0                  0         32768 i
 *>  2.2.2.0/24       12.12.12.2               0             0 200 i
 *>  3.3.3.0/24       13.13.13.3               0             0 300 i
 r>i 4.4.4.0/24       14.14.14.4               0    100      0 i
R1(config-router)#

R1 is not yet advertising default route into BGP. It shows that simply redistributing a default route into BGP would not help. Let’s add a ‘default-information originate’ under BGP.

R1(config-router)#router bgp 100
R1(config-router)#default-information originate
R1(config-router)#do sh run | s bgp
router bgp 100
 bgp router-id 1.1.1.1
 bgp log-neighbor-changes
 network 1.1.1.0 mask 255.255.255.0
 redistribute static
 neighbor 12.12.12.2 remote-as 200
 neighbor 13.13.13.3 remote-as 300
 neighbor 14.14.14.4 remote-as 100
 neighbor 14.14.14.4 next-hop-self
 default-information originate
R1(config-router)#do sh ip bgp
BGP table version is 11, local router ID is 1.1.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,
              x best-external, a additional-path, c RIB-compressed,
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>  0.0.0.0          0.0.0.0                  0         32768 ?
 *>  1.1.1.0/24       0.0.0.0                  0         32768 i
 *>  2.2.2.0/24       12.12.12.2               0             0 200 i
 *>  3.3.3.0/24       13.13.13.3               0             0 300 i
 r>i 4.4.4.0/24       14.14.14.4               0    100      0 i
R1(config-router)#

Now you can see all BGP peers (iBGP and eBGP) are receiving default route information from R1.

R2#sh ip bgp
BGP table version is 10, local router ID is 2.2.2.2
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,
              x best-external, a additional-path, c RIB-compressed,
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>  0.0.0.0          12.12.12.1               0             0 100 ?
 *>  1.1.1.0/24       12.12.12.1               0             0 100 i
 *>  2.2.2.0/24       0.0.0.0                  0         32768 i
 *>  3.3.3.0/24       12.12.12.1                             0 100 300 i
 *>  4.4.4.0/24       12.12.12.1                             0 100 i
R2#sh ip route 0.0.0.0
Routing entry for 0.0.0.0/0, supernet
  Known via "bgp 200", distance 20, metric 0, candidate default path
  Tag 100, type external
  Last update from 12.12.12.1 00:02:25 ago
  Routing Descriptor Blocks:
  * 12.12.12.1, from 12.12.12.1, 00:02:25 ago
      Route metric is 0, traffic share count is 1
      AS Hops 1
      Route tag 100
      MPLS label: none
R2#

R3#sh ip bgp
BGP table version is 8, local router ID is 3.3.3.3
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,
              x best-external, a additional-path, c RIB-compressed,
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>  0.0.0.0          13.13.13.1               0             0 100 ?
 *>  1.1.1.0/24       13.13.13.1               0             0 100 i
 *>  2.2.2.0/24       13.13.13.1                             0 100 200 i
 *>  3.3.3.0/24       0.0.0.0                  0         32768 i
 *>  4.4.4.0/24       13.13.13.1                             0 100 i
R3#sh ip route 0.0.0.0
Routing entry for 0.0.0.0/0, supernet
  Known via "bgp 300", distance 20, metric 0, candidate default path
  Tag 100, type external
  Last update from 13.13.13.1 00:04:36 ago
  Routing Descriptor Blocks:
  * 13.13.13.1, from 13.13.13.1, 00:04:36 ago
      Route metric is 0, traffic share count is 1
      AS Hops 1
      Route tag 100
      MPLS label: none
R3#

R4#sh ip bgp
BGP table version is 8, local router ID is 4.4.4.4
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,
              x best-external, a additional-path, c RIB-compressed,
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>i 0.0.0.0          14.14.14.1               0    100      0 ?
 r>i 1.1.1.0/24       14.14.14.1               0    100      0 i
 *>i 2.2.2.0/24       14.14.14.1               0    100      0 200 i
 *>i 3.3.3.0/24       14.14.14.1               0    100      0 300 i
 *>  4.4.4.0/24       0.0.0.0                  0         32768 i
R4#sh ip route 0.0.0.0
Routing entry for 0.0.0.0/0, supernet
  Known via "bgp 100", distance 200, metric 0, candidate default path, type internal
  Last update from 14.14.14.1 00:05:21 ago
  Routing Descriptor Blocks:
  * 14.14.14.1, from 14.14.14.1, 00:05:21 ago
      Route metric is 0, traffic share count is 1
      AS Hops 0
      MPLS label: none

2. network 0.0.0.0

A default route can be injected into BGP with configuration of ‘network 0.0.0.0’ under BGP if a default route is available in the local routing table of a router.

Following conditions must be fulfilled to use this method.

– A default route must be in the local routing table.
– Add ‘network 0.0.0.0’ under router bgp <ASN>

Let’s remove previously configured ‘default-information originate’ and ‘redistribute static’ commands and use ‘network 0.0.0.0’.

R1#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
R1(config)#router bgp 100
R1(config-router)#no default-information originate
R1(config-router)#no redistribute static
R1(config-router)#network 0.0.0.0
R1(config-router)#do sh run | s bgp
router bgp 100
 bgp router-id 1.1.1.1
 bgp log-neighbor-changes
 network 0.0.0.0
 network 1.1.1.0 mask 255.255.255.0
 neighbor 12.12.12.2 remote-as 200
 neighbor 13.13.13.3 remote-as 300
 neighbor 14.14.14.4 remote-as 100
 neighbor 14.14.14.4 next-hop-self
R1(config-router)#end
R1#sh ip
*Mar 24 11:42:36.623: %SYS-5-CONFIG_I: Configured from console by console
R1#sh ip bgp
BGP table version is 13, local router ID is 1.1.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,
              x best-external, a additional-path, c RIB-compressed,
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>  0.0.0.0          0.0.0.0                  0         32768 i
 *>  1.1.1.0/24       0.0.0.0                  0         32768 i
 *>  2.2.2.0/24       12.12.12.2               0             0 200 i
 *>  3.3.3.0/24       13.13.13.3               0             0 300 i
 r>i 4.4.4.0/24       14.14.14.4               0    100      0 i
R1#

Let’s verify BGP table and default route on peer routers.

R2#sh ip bgp
BGP table version is 12, local router ID is 2.2.2.2
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,
              x best-external, a additional-path, c RIB-compressed,
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>  0.0.0.0          12.12.12.1               0             0 100 i
 *>  1.1.1.0/24       12.12.12.1               0             0 100 i
 *>  2.2.2.0/24       0.0.0.0                  0         32768 i
 *>  3.3.3.0/24       12.12.12.1                             0 100 300 i
 *>  4.4.4.0/24       12.12.12.1                             0 100 i
R2#sh ip route 0.0.0.0
Routing entry for 0.0.0.0/0, supernet
  Known via "bgp 200", distance 20, metric 0, candidate default path
  Tag 100, type external
  Last update from 12.12.12.1 00:01:54 ago
  Routing Descriptor Blocks:
  * 12.12.12.1, from 12.12.12.1, 00:01:54 ago
      Route metric is 0, traffic share count is 1
      AS Hops 1
      Route tag 100
      MPLS label: none

R3#sh ip bgp
BGP table version is 10, local router ID is 3.3.3.3
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,
              x best-external, a additional-path, c RIB-compressed,
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>  0.0.0.0          13.13.13.1               0             0 100 i
 *>  1.1.1.0/24       13.13.13.1               0             0 100 i
 *>  2.2.2.0/24       13.13.13.1                             0 100 200 i
 *>  3.3.3.0/24       0.0.0.0                  0         32768 i
 *>  4.4.4.0/24       13.13.13.1                             0 100 i
R3#sh ip route 0.0.0.0
Routing entry for 0.0.0.0/0, supernet
  Known via "bgp 300", distance 20, metric 0, candidate default path
  Tag 100, type external
  Last update from 13.13.13.1 00:02:17 ago
  Routing Descriptor Blocks:
  * 13.13.13.1, from 13.13.13.1, 00:02:17 ago
      Route metric is 0, traffic share count is 1
      AS Hops 1
      Route tag 100
      MPLS label: none

R4#sh ip bgp
BGP table version is 10, local router ID is 4.4.4.4
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,
              x best-external, a additional-path, c RIB-compressed,
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>i 0.0.0.0          14.14.14.1               0    100      0 i
 r>i 1.1.1.0/24       14.14.14.1               0    100      0 i
 *>i 2.2.2.0/24       14.14.14.1               0    100      0 200 i
 *>i 3.3.3.0/24       14.14.14.1               0    100      0 300 i
 *>  4.4.4.0/24       0.0.0.0                  0         32768 i
R4#sh ip route 0.0.0.0
Routing entry for 0.0.0.0/0, supernet
  Known via "bgp 100", distance 200, metric 0, candidate default path, type internal
  Last update from 14.14.14.1 00:03:06 ago
  Routing Descriptor Blocks:
  * 14.14.14.1, from 14.14.14.1, 00:03:06 ago
      Route metric is 0, traffic share count is 1
      AS Hops 0
      MPLS label: none

3. neighbor x.x.x.x default-originate

If you want to advertise default route to a specific peer, this is the method for that requirement.

– Add ‘neighbor x.x.x.x default-originate’ under router bgp <ASN>
– It does not even check for the existence of a default route in the IP routing table
– The ‘default-information originate’ command should not be configured with the ‘neighbor x.x.x.x default-originate’ command on the same router

Let’s remove previously configured commands.

R1#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
R1(config)#no ip route 0.0.0.0 0.0.0.0 Null0
R1(config)#router bgp 100
R1(config-router)#no  network 0.0.0.0
R1(config-router)#end
R1#sh run
*Mar 24 11:50:22.479: %SYS-5-CONFIG_I: Configured from console by console
R1#sh run | s bgp
router bgp 100
 bgp router-id 1.1.1.1
 bgp log-neighbor-changes
 network 1.1.1.0 mask 255.255.255.0
 neighbor 12.12.12.2 remote-as 200
 neighbor 13.13.13.3 remote-as 300
 neighbor 14.14.14.4 remote-as 100
 neighbor 14.14.14.4 next-hop-self
R1#sh ip route 0.0.0.0
% Network not in table
R1#sh ip bgp
BGP table version is 14, local router ID is 1.1.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,
              x best-external, a additional-path, c RIB-compressed,
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>  1.1.1.0/24       0.0.0.0                  0         32768 i
 *>  2.2.2.0/24       12.12.12.2               0             0 200 i
 *>  3.3.3.0/24       13.13.13.3               0             0 300 i
 r>i 4.4.4.0/24       14.14.14.4               0    100      0 i

Now advertise default route only to R2.

R1#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
R1(config)#router bgp 100
R1(config-router)#neighbor 12.12.12.2 default-originate
R1(config-router)#end
R1#s
*Mar 24 11:53:46.471: %SYS-5-CONFIG_I: Configured from console by consoleh
R1#sh run | s bgp
router bgp 100
 bgp router-id 1.1.1.1
 bgp log-neighbor-changes
 network 1.1.1.0 mask 255.255.255.0
 neighbor 12.12.12.2 remote-as 200
 neighbor 12.12.12.2 default-originate
 neighbor 13.13.13.3 remote-as 300
 neighbor 14.14.14.4 remote-as 100
 neighbor 14.14.14.4 next-hop-self
R1#clear ip bgp 12.12.12.2 soft
R1#sh ip bgp
BGP table version is 15, local router ID is 1.1.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,
              x best-external, a additional-path, c RIB-compressed,
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
     0.0.0.0          0.0.0.0                                0 i
 *>  1.1.1.0/24       0.0.0.0                  0         32768 i
 *>  2.2.2.0/24       12.12.12.2               0             0 200 i
 *>  3.3.3.0/24       13.13.13.3               0             0 300 i
 r>i 4.4.4.0/24       14.14.14.4               0    100      0 i
R1#sh ip route 0.0.0.0
% Network not in table
R1#

Notice there is no default route available in local routing table of R1 and bgp table also shows there is no best route (no *> status) for 0.0.0.0 network.

Let’s verify what R1 is advertising to its peers.

R1#sh ip bgp neighbors 12.12.12.2 advertised-routes
BGP table version is 15, local router ID is 1.1.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,
              x best-external, a additional-path, c RIB-compressed,
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

Originating default network 0.0.0.0

     Network          Next Hop            Metric LocPrf Weight Path
 *>  1.1.1.0/24       0.0.0.0                  0         32768 i
 *>  3.3.3.0/24       13.13.13.3               0             0 300 i
 r>i 4.4.4.0/24       14.14.14.4               0    100      0 i

Total number of prefixes 3

R1#sh ip bgp neighbors 13.13.13.3 advertised-routes
BGP table version is 15, local router ID is 1.1.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,
              x best-external, a additional-path, c RIB-compressed,
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>  1.1.1.0/24       0.0.0.0                  0         32768 i
 *>  2.2.2.0/24       12.12.12.2               0             0 200 i
 *>  3.3.3.0/24       13.13.13.3               0             0 300 i
 r>i 4.4.4.0/24       14.14.14.4               0    100      0 i

Total number of prefixes 4

## No default route advertised to R3(13.13.13.3)

Finally, verify BGP table and routing table on all peer routers.

R2#sh ip bgp
BGP table version is 14, local router ID is 2.2.2.2
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,
              x best-external, a additional-path, c RIB-compressed,
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>  0.0.0.0          12.12.12.1                             0 100 i
 *>  1.1.1.0/24       12.12.12.1               0             0 100 i
 *>  2.2.2.0/24       0.0.0.0                  0         32768 i
 *>  3.3.3.0/24       12.12.12.1                             0 100 300 i
 *>  4.4.4.0/24       12.12.12.1                             0 100 i
R2#sh ip route 0.0.0.0
Routing entry for 0.0.0.0/0, supernet
  Known via "bgp 200", distance 20, metric 0, candidate default path
  Tag 100, type external
  Last update from 12.12.12.1 00:08:27 ago
  Routing Descriptor Blocks:
  * 12.12.12.1, from 12.12.12.1, 00:08:27 ago
      Route metric is 0, traffic share count is 1
      AS Hops 1
      Route tag 100
      MPLS label: none

R3#sh ip bgp
BGP table version is 11, local router ID is 3.3.3.3
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,
              x best-external, a additional-path, c RIB-compressed,
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>  1.1.1.0/24       13.13.13.1               0             0 100 i
 *>  2.2.2.0/24       13.13.13.1                             0 100 200 i
 *>  3.3.3.0/24       0.0.0.0                  0         32768 i
 *>  4.4.4.0/24       13.13.13.1                             0 100 i
R3#sh ip route 0.0.0.0
% Network not in table

R4#sh ip bgp
BGP table version is 11, local router ID is 4.4.4.4
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,
              x best-external, a additional-path, c RIB-compressed,
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 r>i 1.1.1.0/24       14.14.14.1               0    100      0 i
 *>i 2.2.2.0/24       14.14.14.1               0    100      0 200 i
 *>i 3.3.3.0/24       14.14.14.1               0    100      0 300 i
 *>  4.4.4.0/24       0.0.0.0                  0         32768 i
R4#sh ip route 0.0.0.0
% Network not in table

Amolak Networks

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Tag Archives: BGP

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