Monthly Archives: June 2015

OSPF Route Summarization

June 18, 2015Cisco IOS, OSPFExternal Route, Inter-Area Route, OSPF, Route SummarizationAmolak

Consolidation of multiple routes into one single advertisement is called Route Summarization. In a nut shell, route summarization is the process of summarizing subnets into a larger subnet to be advertised to upstream routers for ease of management/troubleshooting and resource conservation.

There are two types of route summarization in OSPF.

1. Inter-Area Route Summarization

Although summarization could be configured between any two areas, it is better to summarize in the direction of the backbone. This way the backbone receives all the aggregate addresses and in turn will injects them, already summarized, into other areas.

Inter-Area route summarization can only be done on the Area Boarder Router (ABR) and summarize routes from one particular area into the another Area.

To specify an address range, perform the following task in router configuration mode:

area area-id range address mask

Where the “area-id” is the area containing networks to be summarized. The “address” and “mask” will specify the range of addresses to be summarized in one range.

2. External Route Summarization

External route summarization is specific to external routes that are injected into OSPF via redistribution.
Summarization is done via the following router ospf subcommand:

summary-address ip-address mask

This command is effective only on ASBRs doing redistribution into OSPF.

We will use following network topology for our discussion.

Pre-Configuration

R1:

interface FastEthernet0/0
 ip address 10.10.123.1 255.255.255.0
!
interface FastEthernet0/1
 ip address 192.168.16.1 255.255.255.0
!
router eigrp 100
 redistribute ospf 1
 network 192.168.16.1 0.0.0.0
 default-metric 10000 100 255 1 1500
 no auto-summary
!
router ospf 1
 router-id 1.1.1.1
 summary-address 192.168.0.0 255.255.0.0
 redistribute eigrp 100 subnets
 network 10.0.0.0 0.255.255.255 area 0


R2:

interface FastEthernet0/0
 ip address 10.10.123.2 255.255.255.0
!
interface FastEthernet0/1
 ip address 10.10.24.2 255.255.255.0
 ip ospf network point-to-point
!
router ospf 1
 router-id 2.2.2.2
 network 10.10.24.2 0.0.0.0 area 1
 network 10.10.123.2 0.0.0.0 area 0


R3:

interface FastEthernet0/0
 ip address 10.10.123.3 255.255.255.0
!
interface FastEthernet0/1
 ip address 10.10.35.3 255.255.255.0
 ip ospf network point-to-point
!
router ospf 1
 router-id 3.3.3.3
 network 10.10.35.3 0.0.0.0 area 2
 network 10.10.123.3 0.0.0.0 area 0


R4:

interface Loopback4
 ip address 10.4.4.1 255.255.255.0
 ip ospf network point-to-point
!
interface Loopback5
 ip address 10.4.5.1 255.255.255.0
 ip ospf network point-to-point
!
interface Loopback6
 ip address 10.4.6.1 255.255.255.0
 ip ospf network point-to-point
!         
interface Loopback7
 ip address 10.4.7.1 255.255.255.0
 ip ospf network point-to-point
!
interface FastEthernet0/0
 ip address 10.10.24.4 255.255.255.0
 ip ospf network point-to-point
!
router ospf 1
 router-id 4.4.4.4
 network 10.0.0.0 0.255.255.255 area 1

R5:

interface Loopback0
 ip address 10.5.0.1 255.255.255.0
 ip ospf network point-to-point
!
interface Loopback1
 ip address 10.5.1.1 255.255.255.0
 ip ospf network point-to-point
!
interface Loopback2
 ip address 10.5.2.1 255.255.255.0
 ip ospf network point-to-point
!
interface Loopback3
 ip address 10.5.3.1 255.255.255.0
 ip ospf network point-to-point
!
interface FastEthernet0/0
 ip address 10.10.35.5 255.255.255.0
 ip ospf network point-to-point
!
router ospf 1
 router-id 5.5.5.5
 network 10.0.0.0 0.255.255.255 area 2

R6:

interface Loopback0
 ip address 192.168.0.1 255.255.255.0
!
interface Loopback1
 ip address 192.168.1.1 255.255.255.0
!
interface Loopback2
 ip address 192.168.2.1 255.255.255.0
!
interface Loopback3
 ip address 192.168.3.1 255.255.255.0
!         
interface FastEthernet0/0
 ip address 192.168.16.6 255.255.255.0
!
router eigrp 100
 network 192.168.0.0 0.0.255.255
 no auto-summary

Note: Loopback Interfaces are used to simulate different networks connected to routers.

OSPF neighborships are UP and all routers have end-to-end network reachability.

R1#sh ip ospf neighbor

Neighbor ID     Pri   State           Dead Time   Address         Interface
2.2.2.2           1   FULL/BDR        00:00:34    10.10.123.2     FastEthernet0/0
3.3.3.3           1   FULL/DR         00:00:31    10.10.123.3     FastEthernet0/0

R2#sh ip ospf neighbor

Neighbor ID     Pri   State           Dead Time   Address         Interface
1.1.1.1           1   FULL/DROTHER    00:00:31    10.10.123.1     FastEthernet0/0
3.3.3.3           1   FULL/DR         00:00:31    10.10.123.3     FastEthernet0/0
4.4.4.4           0   FULL/  -        00:00:34    10.10.24.4      FastEthernet0/1

R3#sh ip ospf neighbor

Neighbor ID     Pri   State           Dead Time   Address         Interface
1.1.1.1           1   FULL/DROTHER    00:00:31    10.10.123.1     FastEthernet0/0
2.2.2.2           1   FULL/BDR        00:00:34    10.10.123.2     FastEthernet0/0
5.5.5.5           0   FULL/  -        00:00:33    10.10.35.5      FastEthernet0/1

R4#sh ip ospf neighbor

Neighbor ID     Pri   State           Dead Time   Address         Interface
2.2.2.2           0   FULL/  -        00:00:32    10.10.24.2      FastEthernet0/0

R5#sh ip ospf neighbor

Neighbor ID     Pri   State           Dead Time   Address         Interface
3.3.3.3           0   FULL/  -        00:00:38    10.10.35.3      FastEthernet0/0

R6#sh ip eigrp neighbors 
IP-EIGRP neighbors for process 100
H   Address                 Interface       Hold Uptime   SRTT   RTO  Q  Seq
                                            (sec)         (ms)       Cnt Num
0   192.168.16.1            Fa0/0             13 02:30:57   28   675  0  50

Routing Tables:

R1#show ip route | b Gateway
Gateway of last resort is not set

     10.0.0.0/24 is subnetted, 11 subnets
O IA    10.4.6.0 [110/3] via 10.10.123.2, 00:29:13, FastEthernet0/0
O IA    10.4.7.0 [110/3] via 10.10.123.2, 00:29:13, FastEthernet0/0
O IA    10.4.4.0 [110/3] via 10.10.123.2, 00:29:08, FastEthernet0/0
O IA    10.4.5.0 [110/3] via 10.10.123.2, 00:29:13, FastEthernet0/0
O IA    10.5.3.0 [110/3] via 10.10.123.3, 00:28:53, FastEthernet0/0
O IA    10.5.2.0 [110/3] via 10.10.123.3, 00:27:46, FastEthernet0/0
O IA    10.5.1.0 [110/3] via 10.10.123.3, 00:27:46, FastEthernet0/0
O IA    10.5.0.0 [110/3] via 10.10.123.3, 00:27:56, FastEthernet0/0
O IA    10.10.24.0 [110/2] via 10.10.123.2, 00:30:27, FastEthernet0/0
O IA    10.10.35.0 [110/2] via 10.10.123.3, 00:30:27, FastEthernet0/0
C       10.10.123.0 is directly connected, FastEthernet0/0
D    192.168.0.0/24 [90/156160] via 192.168.16.6, 02:30:25, FastEthernet0/1
C    192.168.16.0/24 is directly connected, FastEthernet0/1
D    192.168.1.0/24 [90/156160] via 192.168.16.6, 02:30:26, FastEthernet0/1
D    192.168.2.0/24 [90/156160] via 192.168.16.6, 02:30:26, FastEthernet0/1
D    192.168.3.0/24 [90/156160] via 192.168.16.6, 01:06:06, FastEthernet0/1

R2#show ip route | b Gateway
Gateway of last resort is not set

     10.0.0.0/24 is subnetted, 11 subnets
O       10.4.6.0 [110/2] via 10.10.24.4, 00:29:13, FastEthernet0/1
O       10.4.7.0 [110/2] via 10.10.24.4, 00:29:13, FastEthernet0/1
O       10.4.4.0 [110/2] via 10.10.24.4, 00:29:13, FastEthernet0/1
O       10.4.5.0 [110/2] via 10.10.24.4, 00:29:13, FastEthernet0/1
O IA    10.5.3.0 [110/3] via 10.10.123.3, 00:28:53, FastEthernet0/0
O IA    10.5.2.0 [110/3] via 10.10.123.3, 00:27:46, FastEthernet0/0
O IA    10.5.1.0 [110/3] via 10.10.123.3, 00:27:46, FastEthernet0/0
O IA    10.5.0.0 [110/3] via 10.10.123.3, 00:27:56, FastEthernet0/0
C       10.10.24.0 is directly connected, FastEthernet0/1
O IA    10.10.35.0 [110/2] via 10.10.123.3, 00:29:13, FastEthernet0/0
C       10.10.123.0 is directly connected, FastEthernet0/0
O E2 192.168.0.0/24 [110/20] via 10.10.123.1, 00:29:13, FastEthernet0/0
O E2 192.168.16.0/24 [110/20] via 10.10.123.1, 00:29:13, FastEthernet0/0
O E2 192.168.1.0/24 [110/20] via 10.10.123.1, 00:29:13, FastEthernet0/0
O E2 192.168.2.0/24 [110/20] via 10.10.123.1, 00:29:14, FastEthernet0/0
O E2 192.168.3.0/24 [110/20] via 10.10.123.1, 00:29:14, FastEthernet0/0


R3#show ip route | b Gateway
Gateway of last resort is not set

     10.0.0.0/24 is subnetted, 11 subnets
O IA    10.4.6.0 [110/3] via 10.10.123.2, 00:28:53, FastEthernet0/0
O IA    10.4.7.0 [110/3] via 10.10.123.2, 00:28:53, FastEthernet0/0
O IA    10.4.4.0 [110/3] via 10.10.123.2, 00:28:53, FastEthernet0/0
O IA    10.4.5.0 [110/3] via 10.10.123.2, 00:28:53, FastEthernet0/0
O       10.5.3.0 [110/2] via 10.10.35.5, 00:28:53, FastEthernet0/1
O       10.5.2.0 [110/2] via 10.10.35.5, 00:27:46, FastEthernet0/1
O       10.5.1.0 [110/2] via 10.10.35.5, 00:27:46, FastEthernet0/1
O       10.5.0.0 [110/2] via 10.10.35.5, 00:27:56, FastEthernet0/1
O IA    10.10.24.0 [110/2] via 10.10.123.2, 00:28:53, FastEthernet0/0
C       10.10.35.0 is directly connected, FastEthernet0/1
C       10.10.123.0 is directly connected, FastEthernet0/0
O E2 192.168.0.0/24 [110/20] via 10.10.123.1, 00:28:53, FastEthernet0/0
O E2 192.168.16.0/24 [110/20] via 10.10.123.1, 00:28:53, FastEthernet0/0
O E2 192.168.1.0/24 [110/20] via 10.10.123.1, 00:28:53, FastEthernet0/0
O E2 192.168.2.0/24 [110/20] via 10.10.123.1, 00:28:54, FastEthernet0/0
O E2 192.168.3.0/24 [110/20] via 10.10.123.1, 00:28:54, FastEthernet0/0

R4#show ip route | b Gateway
Gateway of last resort is not set

     10.0.0.0/24 is subnetted, 11 subnets
C       10.4.6.0 is directly connected, Loopback6
C       10.4.7.0 is directly connected, Loopback7
C       10.4.4.0 is directly connected, Loopback4
C       10.4.5.0 is directly connected, Loopback5
O IA    10.5.3.0 [110/4] via 10.10.24.2, 00:28:53, FastEthernet0/0
O IA    10.5.2.0 [110/4] via 10.10.24.2, 00:27:46, FastEthernet0/0
O IA    10.5.1.0 [110/4] via 10.10.24.2, 00:27:46, FastEthernet0/0
O IA    10.5.0.0 [110/4] via 10.10.24.2, 00:27:56, FastEthernet0/0
C       10.10.24.0 is directly connected, FastEthernet0/0
O IA    10.10.35.0 [110/3] via 10.10.24.2, 00:30:27, FastEthernet0/0
O IA    10.10.123.0 [110/2] via 10.10.24.2, 00:30:57, FastEthernet0/0
O E2 192.168.0.0/24 [110/20] via 10.10.24.2, 00:29:24, FastEthernet0/0
O E2 192.168.16.0/24 [110/20] via 10.10.24.2, 00:29:29, FastEthernet0/0
O E2 192.168.1.0/24 [110/20] via 10.10.24.2, 00:29:29, FastEthernet0/0
O E2 192.168.2.0/24 [110/20] via 10.10.24.2, 00:29:29, FastEthernet0/0
O E2 192.168.3.0/24 [110/20] via 10.10.24.2, 00:29:31, FastEthernet0/0

R5#show ip route | b Gateway
Gateway of last resort is not set

     10.0.0.0/24 is subnetted, 11 subnets
O IA    10.4.6.0 [110/4] via 10.10.35.3, 00:29:12, FastEthernet0/0
O IA    10.4.7.0 [110/4] via 10.10.35.3, 00:29:12, FastEthernet0/0
O IA    10.4.4.0 [110/4] via 10.10.35.3, 00:29:03, FastEthernet0/0
O IA    10.4.5.0 [110/4] via 10.10.35.3, 00:29:12, FastEthernet0/0
C       10.5.3.0 is directly connected, Loopback3
C       10.5.2.0 is directly connected, Loopback2
C       10.5.1.0 is directly connected, Loopback1
C       10.5.0.0 is directly connected, Loopback0
O IA    10.10.24.0 [110/3] via 10.10.35.3, 00:30:27, FastEthernet0/0
C       10.10.35.0 is directly connected, FastEthernet0/0
O IA    10.10.123.0 [110/2] via 10.10.35.3, 00:30:57, FastEthernet0/0
O E2 192.168.0.0/24 [110/20] via 10.10.35.3, 00:29:24, FastEthernet0/0
O E2 192.168.16.0/24 [110/20] via 10.10.35.3, 00:29:29, FastEthernet0/0
O E2 192.168.1.0/24 [110/20] via 10.10.35.3, 00:29:29, FastEthernet0/0
O E2 192.168.2.0/24 [110/20] via 10.10.35.3, 00:29:29, FastEthernet0/0
O E2 192.168.3.0/24 [110/20] via 10.10.35.3, 00:29:31, FastEthernet0/0

R6#show ip route | b Gateway
Gateway of last resort is not set

     10.0.0.0/24 is subnetted, 11 subnets
D EX    10.4.6.0 [170/284160] via 192.168.16.1, 00:29:12, FastEthernet0/0
D EX    10.4.7.0 [170/284160] via 192.168.16.1, 00:29:12, FastEthernet0/0
D EX    10.4.4.0 [170/284160] via 192.168.16.1, 00:29:08, FastEthernet0/0
D EX    10.4.5.0 [170/284160] via 192.168.16.1, 00:29:12, FastEthernet0/0
D EX    10.5.3.0 [170/284160] via 192.168.16.1, 00:28:53, FastEthernet0/0
D EX    10.5.2.0 [170/284160] via 192.168.16.1, 00:27:46, FastEthernet0/0
D EX    10.5.1.0 [170/284160] via 192.168.16.1, 00:27:46, FastEthernet0/0
D EX    10.5.0.0 [170/284160] via 192.168.16.1, 00:27:56, FastEthernet0/0
D EX    10.10.24.0 [170/284160] via 192.168.16.1, 00:30:27, FastEthernet0/0
D EX    10.10.35.0 [170/284160] via 192.168.16.1, 00:30:27, FastEthernet0/0
D EX    10.10.123.0 [170/284160] via 192.168.16.1, 02:12:11, FastEthernet0/0
C    192.168.0.0/24 is directly connected, Loopback0
C    192.168.16.0/24 is directly connected, FastEthernet0/0
C    192.168.1.0/24 is directly connected, Loopback1
C    192.168.2.0/24 is directly connected, Loopback2
C    192.168.3.0/24 is directly connected, Loopback3

First we want to summarize Area 1 routes. R2 is the ABR (Area Border Router), connecting Area1 to Backbone Area (Area 0). Here, R2 will do the inter-area route summarization and send summary advertisement into Area 0.

These four IP subnets can be summarized as follows:

10.4.4.0/24
10.4.5.0/24
10.4.6.0/24
10.4.7.0/24

Summary Network: 10.4.4.0
Mask: 255.255.252.0

R2#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
R2(config)#router ospf 1
R2(config-router)#area 1 range 10.4.4.0 255.255.252.0
R2(config-router)#end
R2#

Let’s see the changes in routing tables on other routers

R1 Before Route Summarization:

R1#show ip route | b Gateway
Gateway of last resort is not set

     10.0.0.0/24 is subnetted, 11 subnets
O IA    10.4.6.0 [110/3] via 10.10.123.2, 00:29:13, FastEthernet0/0
O IA    10.4.7.0 [110/3] via 10.10.123.2, 00:29:13, FastEthernet0/0
O IA    10.4.4.0 [110/3] via 10.10.123.2, 00:29:08, FastEthernet0/0
O IA    10.4.5.0 [110/3] via 10.10.123.2, 00:29:13, FastEthernet0/0
O IA    10.5.3.0 [110/3] via 10.10.123.3, 00:28:53, FastEthernet0/0
O IA    10.5.2.0 [110/3] via 10.10.123.3, 00:27:46, FastEthernet0/0
O IA    10.5.1.0 [110/3] via 10.10.123.3, 00:27:46, FastEthernet0/0
O IA    10.5.0.0 [110/3] via 10.10.123.3, 00:27:56, FastEthernet0/0
O IA    10.10.24.0 [110/2] via 10.10.123.2, 00:30:27, FastEthernet0/0
O IA    10.10.35.0 [110/2] via 10.10.123.3, 00:30:27, FastEthernet0/0
C       10.10.123.0 is directly connected, FastEthernet0/0
D    192.168.0.0/24 [90/156160] via 192.168.16.6, 02:30:25, FastEthernet0/1
C    192.168.16.0/24 is directly connected, FastEthernet0/1
D    192.168.1.0/24 [90/156160] via 192.168.16.6, 02:30:26, FastEthernet0/1
D    192.168.2.0/24 [90/156160] via 192.168.16.6, 02:30:26, FastEthernet0/1
D    192.168.3.0/24 [90/156160] via 192.168.16.6, 01:06:06, FastEthernet0/1

R1 After Route Summarization:

R1#show ip route | b Gateway
Gateway of last resort is not set

     10.0.0.0/8 is variably subnetted, 8 subnets, 2 masks
O IA    10.4.4.0/22 [110/3] via 10.10.123.2, 00:01:47, FastEthernet0/0
O IA    10.5.3.0/24 [110/3] via 10.10.123.3, 00:56:18, FastEthernet0/0
O IA    10.5.2.0/24 [110/3] via 10.10.123.3, 00:55:11, FastEthernet0/0
O IA    10.5.1.0/24 [110/3] via 10.10.123.3, 00:55:11, FastEthernet0/0
O IA    10.5.0.0/24 [110/3] via 10.10.123.3, 00:55:21, FastEthernet0/0
O IA    10.10.24.0/24 [110/2] via 10.10.123.2, 00:57:52, FastEthernet0/0
O IA    10.10.35.0/24 [110/2] via 10.10.123.3, 00:57:52, FastEthernet0/0
C       10.10.123.0/24 is directly connected, FastEthernet0/0
D    192.168.0.0/24 [90/156160] via 192.168.16.6, 02:57:50, FastEthernet0/1
C    192.168.16.0/24 is directly connected, FastEthernet0/1
D    192.168.1.0/24 [90/156160] via 192.168.16.6, 02:57:49, FastEthernet0/1
D    192.168.2.0/24 [90/156160] via 192.168.16.6, 02:57:49, FastEthernet0/1
D    192.168.3.0/24 [90/156160] via 192.168.16.6, 01:33:29, FastEthernet0/1

R5 Before Route Summarization:

R5#show ip route | b Gateway
Gateway of last resort is not set

     10.0.0.0/24 is subnetted, 11 subnets
O IA    10.4.6.0 [110/4] via 10.10.35.3, 00:29:12, FastEthernet0/0
O IA    10.4.7.0 [110/4] via 10.10.35.3, 00:29:12, FastEthernet0/0
O IA    10.4.4.0 [110/4] via 10.10.35.3, 00:29:03, FastEthernet0/0
O IA    10.4.5.0 [110/4] via 10.10.35.3, 00:29:12, FastEthernet0/0
C       10.5.3.0 is directly connected, Loopback3
C       10.5.2.0 is directly connected, Loopback2
C       10.5.1.0 is directly connected, Loopback1
C       10.5.0.0 is directly connected, Loopback0
O IA    10.10.24.0 [110/3] via 10.10.35.3, 00:30:27, FastEthernet0/0
C       10.10.35.0 is directly connected, FastEthernet0/0
O IA    10.10.123.0 [110/2] via 10.10.35.3, 00:30:57, FastEthernet0/0
O E2 192.168.0.0/24 [110/20] via 10.10.35.3, 00:29:24, FastEthernet0/0
O E2 192.168.16.0/24 [110/20] via 10.10.35.3, 00:29:29, FastEthernet0/0
O E2 192.168.1.0/24 [110/20] via 10.10.35.3, 00:29:29, FastEthernet0/0
O E2 192.168.2.0/24 [110/20] via 10.10.35.3, 00:29:29, FastEthernet0/0
O E2 192.168.3.0/24 [110/20] via 10.10.35.3, 00:29:31, FastEthernet0/0

R5 After Route Summarization:

R5#show ip route | b Gateway
Gateway of last resort is not set

     10.0.0.0/8 is variably subnetted, 8 subnets, 2 masks
O IA    10.4.4.0/22 [110/4] via 10.10.35.3, 00:06:30, FastEthernet0/0
C       10.5.3.0/24 is directly connected, Loopback3
C       10.5.2.0/24 is directly connected, Loopback2
C       10.5.1.0/24 is directly connected, Loopback1
C       10.5.0.0/24 is directly connected, Loopback0
O IA    10.10.24.0/24 [110/3] via 10.10.35.3, 01:02:34, FastEthernet0/0
C       10.10.35.0/24 is directly connected, FastEthernet0/0
O IA    10.10.123.0/24 [110/2] via 10.10.35.3, 01:03:04, FastEthernet0/0
O E2 192.168.0.0/24 [110/20] via 10.10.35.3, 01:01:32, FastEthernet0/0
O E2 192.168.16.0/24 [110/20] via 10.10.35.3, 01:01:36, FastEthernet0/0
O E2 192.168.1.0/24 [110/20] via 10.10.35.3, 01:01:36, FastEthernet0/0
O E2 192.168.2.0/24 [110/20] via 10.10.35.3, 01:01:36, FastEthernet0/0
O E2 192.168.3.0/24 [110/20] via 10.10.35.3, 01:01:36, FastEthernet0/0

Let’s do the same for Area 2. R3 is the ABR here and doing the route summarization for following networks.

10.5.0.0/24
10.5.1.0/24
10.5.2.0/24
10.5.3.0/24

Summary Network: 10.5.0.0
Mask: 255.255.252.0

R3#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
R3(config)#router ospf 1
R3(config-router)#area 2 range 10.5.0.0 255.255.252.0
R3(config-router)#end
R3#

Let’s see the changes in routing tables on other routers

Before Route Summarization:

R1#show ip route | b Gateway
Gateway of last resort is not set

     10.0.0.0/8 is variably subnetted, 8 subnets, 2 masks
O IA    10.4.4.0/22 [110/3] via 10.10.123.2, 00:01:47, FastEthernet0/0
O IA    10.5.3.0/24 [110/3] via 10.10.123.3, 00:56:18, FastEthernet0/0
O IA    10.5.2.0/24 [110/3] via 10.10.123.3, 00:55:11, FastEthernet0/0
O IA    10.5.1.0/24 [110/3] via 10.10.123.3, 00:55:11, FastEthernet0/0
O IA    10.5.0.0/24 [110/3] via 10.10.123.3, 00:55:21, FastEthernet0/0
O IA    10.10.24.0/24 [110/2] via 10.10.123.2, 00:57:52, FastEthernet0/0
O IA    10.10.35.0/24 [110/2] via 10.10.123.3, 00:57:52, FastEthernet0/0
C       10.10.123.0/24 is directly connected, FastEthernet0/0
D    192.168.0.0/24 [90/156160] via 192.168.16.6, 02:57:50, FastEthernet0/1
C    192.168.16.0/24 is directly connected, FastEthernet0/1
D    192.168.1.0/24 [90/156160] via 192.168.16.6, 02:57:49, FastEthernet0/1
D    192.168.2.0/24 [90/156160] via 192.168.16.6, 02:57:49, FastEthernet0/1
D    192.168.3.0/24 [90/156160] via 192.168.16.6, 01:33:29, FastEthernet0/1
R1#

After Route Summarization:

R1#show ip route | b Gateway
Gateway of last resort is not set

     10.0.0.0/8 is variably subnetted, 5 subnets, 2 masks
O IA    10.4.4.0/22 [110/3] via 10.10.123.2, 00:35:14, FastEthernet0/0
O IA    10.5.0.0/22 [110/3] via 10.10.123.3, 00:01:40, FastEthernet0/0
O IA    10.10.24.0/24 [110/2] via 10.10.123.2, 01:31:19, FastEthernet0/0
O IA    10.10.35.0/24 [110/2] via 10.10.123.3, 01:31:19, FastEthernet0/0
C       10.10.123.0/24 is directly connected, FastEthernet0/0
D    192.168.0.0/24 [90/156160] via 192.168.16.6, 03:31:17, FastEthernet0/1
C    192.168.16.0/24 is directly connected, FastEthernet0/1
D    192.168.1.0/24 [90/156160] via 192.168.16.6, 03:31:16, FastEthernet0/1
D    192.168.2.0/24 [90/156160] via 192.168.16.6, 03:31:16, FastEthernet0/1
D    192.168.3.0/24 [90/156160] via 192.168.16.6, 02:06:56, FastEthernet0/1

Let’s summarize external routes now. Router R1 is the ASBR connected to both EIGRP and OSPF domains and doing route redistribution between EIGRP and OSPF.

R1 (ASBR) will do the route summarization for external routes into OSPF.

These four IP subnets can be summarized as follows:

192.168.0.0/24
192.168.1.0/24
192.168.2.0/24
192.168.3.0/24

Summary Network: 192.168.0.0
Mask: 255.255.252.0

R1#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
R1(config)#router ospf 1
R1(config-router)#summary-address 192.168.0.0 255.255.252.0
R1(config-router)#end
R1#

Let’s see the changes in routing tables on other routers

Before Route Summarization:

R2#show ip route | b Gateway
Gateway of last resort is not set

     10.0.0.0/8 is variably subnetted, 12 subnets, 2 masks
O       10.4.6.0/24 [110/2] via 10.10.24.4, 00:03:02, FastEthernet0/1
O       10.4.7.0/24 [110/2] via 10.10.24.4, 00:03:02, FastEthernet0/1
O       10.4.4.0/24 [110/2] via 10.10.24.4, 00:03:02, FastEthernet0/1
O       10.4.4.0/22 is a summary, 00:03:02, Null0
O       10.4.5.0/24 [110/2] via 10.10.24.4, 00:03:02, FastEthernet0/1
O IA    10.5.3.0/24 [110/3] via 10.10.123.3, 00:03:02, FastEthernet0/0
O IA    10.5.2.0/24 [110/3] via 10.10.123.3, 00:03:02, FastEthernet0/0
O IA    10.5.1.0/24 [110/3] via 10.10.123.3, 00:03:02, FastEthernet0/0
O IA    10.5.0.0/24 [110/3] via 10.10.123.3, 00:03:02, FastEthernet0/0
C       10.10.24.0/24 is directly connected, FastEthernet0/1
O IA    10.10.35.0/24 [110/2] via 10.10.123.3, 00:03:02, FastEthernet0/0
C       10.10.123.0/24 is directly connected, FastEthernet0/0
O E2 192.168.0.0/24 [110/20] via 10.10.123.1, 00:03:02, FastEthernet0/0
O E2 192.168.16.0/24 [110/20] via 10.10.123.1, 00:03:03, FastEthernet0/0
O E2 192.168.1.0/24 [110/20] via 10.10.123.1, 00:03:03, FastEthernet0/0
O E2 192.168.2.0/24 [110/20] via 10.10.123.1, 00:03:03, FastEthernet0/0
O E2 192.168.3.0/24 [110/20] via 10.10.123.1, 00:03:03, FastEthernet0/0

After Route Summarization:

R2#show ip route | b Gateway
Gateway of last resort is not set

     10.0.0.0/8 is variably subnetted, 9 subnets, 2 masks
O       10.4.6.0/24 [110/2] via 10.10.24.4, 00:43:59, FastEthernet0/1
O       10.4.7.0/24 [110/2] via 10.10.24.4, 00:43:59, FastEthernet0/1
O       10.4.4.0/24 [110/2] via 10.10.24.4, 00:43:59, FastEthernet0/1
O       10.4.4.0/22 is a summary, 00:43:59, Null0
O       10.4.5.0/24 [110/2] via 10.10.24.4, 00:43:59, FastEthernet0/1
O IA    10.5.0.0/22 [110/3] via 10.10.123.3, 00:10:24, FastEthernet0/0
C       10.10.24.0/24 is directly connected, FastEthernet0/1
O IA    10.10.35.0/24 [110/2] via 10.10.123.3, 00:43:59, FastEthernet0/0
C       10.10.123.0/24 is directly connected, FastEthernet0/0
O E2 192.168.16.0/24 [110/20] via 10.10.123.1, 00:43:59, FastEthernet0/0
O E2 192.168.0.0/22 [110/20] via 10.10.123.1, 00:00:57, FastEthernet0/0
R2#

Let’s see the routing tables on R4 and verify end-to-end connectivity.

Before Route Summarization:

R4#show ip route | b Gateway
Gateway of last resort is not set

     10.0.0.0/24 is subnetted, 11 subnets
C       10.4.6.0 is directly connected, Loopback6
C       10.4.7.0 is directly connected, Loopback7
C       10.4.4.0 is directly connected, Loopback4
C       10.4.5.0 is directly connected, Loopback5
O IA    10.5.3.0 [110/4] via 10.10.24.2, 00:28:53, FastEthernet0/0
O IA    10.5.2.0 [110/4] via 10.10.24.2, 00:27:46, FastEthernet0/0
O IA    10.5.1.0 [110/4] via 10.10.24.2, 00:27:46, FastEthernet0/0
O IA    10.5.0.0 [110/4] via 10.10.24.2, 00:27:56, FastEthernet0/0
C       10.10.24.0 is directly connected, FastEthernet0/0
O IA    10.10.35.0 [110/3] via 10.10.24.2, 00:30:27, FastEthernet0/0
O IA    10.10.123.0 [110/2] via 10.10.24.2, 00:30:57, FastEthernet0/0
O E2 192.168.0.0/24 [110/20] via 10.10.24.2, 00:29:24, FastEthernet0/0
O E2 192.168.16.0/24 [110/20] via 10.10.24.2, 00:29:29, FastEthernet0/0
O E2 192.168.1.0/24 [110/20] via 10.10.24.2, 00:29:29, FastEthernet0/0
O E2 192.168.2.0/24 [110/20] via 10.10.24.2, 00:29:29, FastEthernet0/0
O E2 192.168.3.0/24 [110/20] via 10.10.24.2, 00:29:31, FastEthernet0/0

After Route Summarization:

R4#show ip route | b Gateway
Gateway of last resort is not set

     10.0.0.0/8 is variably subnetted, 8 subnets, 2 masks
C       10.4.6.0/24 is directly connected, Loopback6
C       10.4.7.0/24 is directly connected, Loopback7
C       10.4.4.0/24 is directly connected, Loopback4
C       10.4.5.0/24 is directly connected, Loopback5
O IA    10.5.0.0/22 [110/4] via 10.10.24.2, 00:12:19, FastEthernet0/0
C       10.10.24.0/24 is directly connected, FastEthernet0/0
O IA    10.10.35.0/24 [110/3] via 10.10.24.2, 01:41:58, FastEthernet0/0
O IA    10.10.123.0/24 [110/2] via 10.10.24.2, 01:42:28, FastEthernet0/0
O E2 192.168.16.0/24 [110/20] via 10.10.24.2, 01:41:00, FastEthernet0/0
O E2 192.168.0.0/22 [110/20] via 10.10.24.2, 00:02:51, FastEthernet0/0
R4#

R4#ping 192.168.1.1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.1.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 60/64/84 ms

R4#ping 10.5.1.1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.5.1.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 52/64/88 ms

So far we have seen that when route summarization is configured , either type inter-area or external, it advertise summary route and suppress advertisement of specific network advertisements.

Another point to note is, OSPF router advertise summary routes only if it is receiving advertisement for atleast one route, which falls within the summary network range.

R5 is sending LSA advertisements for networks (10.5.0.0/24, 10.5.1.0/24, 10.5.2.0/24 and 10.5.3.0/24) and R3 is sending a single summary route (10.5.0.0/22) advertisement for those networks.

These Loopback interfaces are simulating different 10.5.x.x networks connected to R5.

R5#sh ip int brief
Interface                  IP-Address      OK? Method Status                Protocol
FastEthernet0/0            10.10.35.5      YES manual up                    up      
FastEthernet0/1            unassigned      YES unset  up                    up      
Loopback0                  10.5.0.1        YES manual up                    up      
Loopback1                  10.5.1.1        YES manual up                    up      
Loopback2                  10.5.2.1        YES manual up                    up      
Loopback3                  10.5.3.1        YES manual up                    up      
R5#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
R5(config)#int l0
R5(config-if)#shut
R5(config-if)#int l1
R5(config-if)#
*Mar  1 04:36:28.214: %LINK-5-CHANGED: Interface Loopback0, changed state to administratively down
*Mar  1 04:36:29.214: %LINEPROTO-5-UPDOWN: Line protocol on Interface Loopback0, changed state to down
R5(config-if)#shut  
R5(config-if)#int l2
R5(config-if)#
*Mar  1 04:36:33.582: %LINK-5-CHANGED: Interface Loopback1, changed state to administratively down
*Mar  1 04:36:34.582: %LINEPROTO-5-UPDOWN: Line protocol on Interface Loopback1, changed state to down
R5(config-if)#shut  
R5(config-if)#
*Mar  1 04:36:37.922: %LINK-5-CHANGED: Interface Loopback2, changed state to administratively down
*Mar  1 04:36:38.922: %LINEPROTO-5-UPDOWN: Line protocol on Interface Loopback2, changed state to down
R5(config-if)#

Loopback 0,1 and 2 are shutdown now.

See routing table on R3, It has route for 10.5.3.0/24 only now, but still sending advertisement for summary route 10.5.0.0/22.

R3#show ip route | b Gateway
Gateway of last resort is not set

     10.0.0.0/8 is variably subnetted, 6 subnets, 2 masks
O IA    10.4.4.0/22 [110/3] via 10.10.123.2, 01:24:03, FastEthernet0/0
O       10.5.3.0/24 [110/2] via 10.10.35.5, 01:24:03, FastEthernet0/1
O       10.5.0.0/22 is a summary, 01:24:03, Null0
O IA    10.10.24.0/24 [110/2] via 10.10.123.2, 01:24:03, FastEthernet0/0
C       10.10.35.0/24 is directly connected, FastEthernet0/1
C       10.10.123.0/24 is directly connected, FastEthernet0/0
O E2 192.168.16.0/24 [110/20] via 10.10.123.1, 01:24:03, FastEthernet0/0
O E2 192.168.0.0/22 [110/20] via 10.10.123.1, 01:14:35, FastEthernet0/0

Routing table on R2, it is still receiving summary advertisement from R3.

R2#show ip route | b Gateway
Gateway of last resort is not set

     10.0.0.0/8 is variably subnetted, 9 subnets, 2 masks
O       10.4.6.0/24 [110/2] via 10.10.24.4, 02:00:05, FastEthernet0/1
O       10.4.7.0/24 [110/2] via 10.10.24.4, 02:00:05, FastEthernet0/1
O       10.4.4.0/24 [110/2] via 10.10.24.4, 02:00:05, FastEthernet0/1
O       10.4.4.0/22 is a summary, 02:00:05, Null0
O       10.4.5.0/24 [110/2] via 10.10.24.4, 02:00:05, FastEthernet0/1
O IA    10.5.0.0/22 [110/3] via 10.10.123.3, 01:26:30, FastEthernet0/0
C       10.10.24.0/24 is directly connected, FastEthernet0/1
O IA    10.10.35.0/24 [110/2] via 10.10.123.3, 02:00:05, FastEthernet0/0
C       10.10.123.0/24 is directly connected, FastEthernet0/0
O E2 192.168.16.0/24 [110/20] via 10.10.123.1, 02:00:05, FastEthernet0/0
O E2 192.168.0.0/22 [110/20] via 10.10.123.1, 01:17:02, FastEthernet0/0

Let’s shutdown interface loopback 3 also on R5.

R5(config-if)#int l3
R5(config-if)#shut
R5(config-if)#
*Mar  1 05:09:59.566: %LINK-5-CHANGED: Interface Loopback3, changed state to administratively down
*Mar  1 05:10:00.566: %LINEPROTO-5-UPDOWN: Line protocol on Interface Loopback3, changed state to down
R5(config-if)#

If we see routing table on R3.It has lost all routes for 10.5.x.x networks, and now it will not send advertisement for summary route.

R3#show ip route | b Gateway
Gateway of last resort is not set

     10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
O IA    10.4.4.0/22 [110/3] via 10.10.123.2, 01:36:57, FastEthernet0/0
O IA    10.10.24.0/24 [110/2] via 10.10.123.2, 01:36:57, FastEthernet0/0
C       10.10.35.0/24 is directly connected, FastEthernet0/1
C       10.10.123.0/24 is directly connected, FastEthernet0/0
O E2 192.168.16.0/24 [110/20] via 10.10.123.1, 01:36:57, FastEthernet0/0
O E2 192.168.0.0/22 [110/20] via 10.10.123.1, 01:27:30, FastEthernet0/0

R2#show ip route | b Gateway
Gateway of last resort is not set

     10.0.0.0/8 is variably subnetted, 8 subnets, 2 masks
O       10.4.6.0/24 [110/2] via 10.10.24.4, 02:11:46, FastEthernet0/1
O       10.4.7.0/24 [110/2] via 10.10.24.4, 02:11:46, FastEthernet0/1
O       10.4.4.0/24 [110/2] via 10.10.24.4, 02:11:46, FastEthernet0/1
O       10.4.4.0/22 is a summary, 02:11:46, Null0
O       10.4.5.0/24 [110/2] via 10.10.24.4, 02:11:46, FastEthernet0/1
C       10.10.24.0/24 is directly connected, FastEthernet0/1
O IA    10.10.35.0/24 [110/2] via 10.10.123.3, 02:11:46, FastEthernet0/0
C       10.10.123.0/24 is directly connected, FastEthernet0/0
O E2 192.168.16.0/24 [110/20] via 10.10.123.1, 02:11:46, FastEthernet0/0
O E2 192.168.0.0/22 [110/20] via 10.10.123.1, 01:28:43, FastEthernet0/0
R2#show ip route 10.5.0.0
% Subnet not in table
R2#

Enable all Loopback interfaces on R5.

R5(config-if)#int l0
R5(config-if)#no shut
R5(config-if)#int l1
R5(config-if)#no shut
R5(config-if)#
*Mar  1 05:20:26.106: %LINK-3-UPDOWN: Interface Loopback0, changed state to up
*Mar  1 05:20:27.106: %LINEPROTO-5-UPDOWN: Line protocol on Interface Loopback0, changed state to up
R5(config-if)#int l2
R5(config-if)#no shu
*Mar  1 05:20:28.898: %LINK-3-UPDOWN: Interface Loopback1, changed state to up
*Mar  1 05:20:29.898: %LINEPROTO-5-UPDOWN: Line protocol on Interface Loopback1, changed state to up
R5(config-if)#no shut
R5(config-if)#int l3
R5(config-if)#no shut
R5(config-if)#
*Mar  1 05:20:32.470: %LINK-3-UPDOWN: Interface Loopback2, changed state to up
*Mar  1 05:20:33.470: %LINEPROTO-5-UPDOWN: Line protocol on Interface Loopback2, changed state to up
R5(config-if)#
*Mar  1 05:20:35.922: %LINK-3-UPDOWN: Interface Loopback3, changed state to up
*Mar  1 05:20:36.922: %LINEPROTO-5-UPDOWN: Line protocol on Interface Loopback3, changed state to up
R5(config-if)#do sh ip int brief
Interface                  IP-Address      OK? Method Status                Protocol
FastEthernet0/0            10.10.35.5      YES manual up                    up      
FastEthernet0/1            unassigned      YES unset  up                    up      
Loopback0                  10.5.0.1        YES manual up                    up      
Loopback1                  10.5.1.1        YES manual up                    up      
Loopback2                  10.5.2.1        YES manual up                    up      
Loopback3                  10.5.3.1        YES manual up                    up      
R5(config-if)#

Now R3 has routes for all those networks and sending advertisement for summary address into Backbone Area.

R3#show ip route | b Gateway
Gateway of last resort is not set

     10.0.0.0/8 is variably subnetted, 9 subnets, 2 masks
O IA    10.4.4.0/22 [110/3] via 10.10.123.2, 01:46:59, FastEthernet0/0
O       10.5.3.0/24 [110/2] via 10.10.35.5, 00:00:31, FastEthernet0/1
O       10.5.2.0/24 [110/2] via 10.10.35.5, 00:00:31, FastEthernet0/1
O       10.5.1.0/24 [110/2] via 10.10.35.5, 00:00:31, FastEthernet0/1
O       10.5.0.0/24 [110/2] via 10.10.35.5, 00:00:41, FastEthernet0/1
O       10.5.0.0/22 is a summary, 00:00:41, Null0
O IA    10.10.24.0/24 [110/2] via 10.10.123.2, 01:46:59, FastEthernet0/0
C       10.10.35.0/24 is directly connected, FastEthernet0/1
C       10.10.123.0/24 is directly connected, FastEthernet0/0
O E2 192.168.16.0/24 [110/20] via 10.10.123.1, 01:46:59, FastEthernet0/0
O E2 192.168.0.0/22 [110/20] via 10.10.123.1, 01:37:31, FastEthernet0/0
R3#

Did you notice this route on R3?

O       10.5.0.0/22 is a summary, 00:00:41, Null0

This is called a discard route.

Prior to Cisco IOS Software Release 12.1(6), it was recommended to manually configure, on the ABR, a discard static route for the summary address in order to prevent possible routing loops. For the summary route shown above, you can use this command:

ip route 10.5.0.0 255.255.252.0 null0

In IOS 12.1(6) and higher, the discard route is automatically generated by default. If for any reason you don’t want to use this discard route, you can configure the following commands under router ospf:

[no] discard-route internal
or
[no] discard-route external

Route Leak between VRFs with Import MAP

June 4, 2015MPLS, Service Providerimport-map, MPLS, VRFAmolak

We will discuss route-leaking between VRFs using different import-map techniques in this session.

Here is the network topology for our discussion.

Task requirement: On R1, VRF AAA should import prefix 10.4.2.0/24 from ASN 444 and 10.6.1.0/24 from ASN 666.

Pre-Configuration of devices:

R1:

hostname R1
!
vrf definition AAA
 rd 333:3
 !
 address-family ipv4
 route-target export 333:3
 route-target import 333:3
 exit-address-family
!
interface Loopback0
 ip address 172.16.0.1 255.255.255.255
 ip ospf 1 area 0
!
interface FastEthernet0/0
 ip address 172.16.12.1 255.255.255.0
 ip ospf network point-to-point
 ip ospf 1 area 0
 mpls ip
!
interface FastEthernet1/0
 vrf forwarding AAA
 ip address 172.16.13.1 255.255.255.0
!
router ospf 1
 log-adjacency-changes
!
router bgp 100
 bgp router-id 172.16.0.1
 no bgp default ipv4-unicast
 no bgp default route-target filter
 bgp log-neighbor-changes
 neighbor 172.16.0.2 remote-as 100
 neighbor 172.16.0.2 update-source Loopback0
 !
 address-family ipv4
  no synchronization
  no auto-summary
 exit-address-family
 !
 address-family vpnv4
  neighbor 172.16.0.2 activate
  neighbor 172.16.0.2 send-community extended
 exit-address-family
 !
 address-family ipv4 vrf AAA
  no synchronization
  redistribute connected
  neighbor 172.16.13.3 remote-as 333
  neighbor 172.16.13.3 activate
 exit-address-family
!
end



R2:


hostname R2
!
vrf definition BBB
 rd 444:4
 !
 address-family ipv4
 route-target export 444:4
 route-target import 444:4
 exit-address-family
!
vrf definition CCC
 rd 666:6
 !
 address-family ipv4
 route-target export 666:6
 route-target import 666:6
 exit-address-family
!
interface Loopback0
 ip address 172.16.0.2 255.255.255.255
 ip ospf 1 area 0
!
interface FastEthernet0/0
 ip address 172.16.12.2 255.255.255.0
 ip ospf network point-to-point
 ip ospf 1 area 0
 mpls ip
!
interface FastEthernet1/0
 vrf forwarding BBB
 ip address 172.16.24.2 255.255.255.0
!
interface FastEthernet1/1
 vrf forwarding CCC
 ip address 172.16.26.2 255.255.255.0
!
router ospf 1
 log-adjacency-changes
!
router bgp 100
 bgp router-id 172.16.0.2
 no bgp default ipv4-unicast
 no bgp default route-target filter
 bgp log-neighbor-changes
 neighbor 172.16.0.1 remote-as 100
 neighbor 172.16.0.1 update-source Loopback0
 !
 address-family ipv4
  no synchronization
  no auto-summary
 exit-address-family
 !
 address-family vpnv4
  neighbor 172.16.0.1 activate
  neighbor 172.16.0.1 send-community extended
 exit-address-family
 !
 address-family ipv4 vrf BBB
  no synchronization
  redistribute connected
  neighbor 172.16.24.4 remote-as 444
  neighbor 172.16.24.4 activate
 exit-address-family
 !
 address-family ipv4 vrf CCC
  no synchronization
  redistribute connected
  neighbor 172.16.26.6 remote-as 666
  neighbor 172.16.26.6 activate
 exit-address-family
!


R3:

hostname R3
!
interface Loopback1
 ip address 10.3.1.1 255.255.255.0
!
interface Loopback2
 ip address 10.3.2.1 255.255.255.0
!
interface FastEthernet0/0
 ip address 172.16.13.3 255.255.255.0
!
router bgp 333
 no synchronization
 bgp router-id 172.16.13.3
 bgp log-neighbor-changes
 network 10.3.1.0 mask 255.255.255.0
 network 10.3.2.0 mask 255.255.255.0
 neighbor 172.16.13.1 remote-as 100
 no auto-summary
!

R4:

hostname R4
!
interface Loopback1
 ip address 10.4.1.1 255.255.255.0
!
interface Loopback2
 ip address 10.4.2.1 255.255.255.0
!
interface Loopback192
 ip address 192.168.1.1 255.255.255.0
!
interface FastEthernet0/0
 ip address 172.16.24.4 255.255.255.0
!
router bgp 444
 no synchronization
 bgp router-id 172.16.24.4
 bgp log-neighbor-changes
 network 10.4.1.0 mask 255.255.255.0
 network 10.4.2.0 mask 255.255.255.0
 network 192.168.1.0
 neighbor 172.16.24.2 remote-as 100
 no auto-summary
!


R6:

hostname R6
!
interface Loopback1
 ip address 10.6.1.1 255.255.255.0
!
interface Loopback2
 ip address 10.6.2.1 255.255.255.0
!
interface Loopback192
 ip address 192.168.1.1 255.255.255.0
!
interface FastEthernet0/0
 ip address 172.16.26.6 255.255.255.0
!
router bgp 666
 no synchronization
 bgp router-id 172.16.26.6
 bgp log-neighbor-changes
 network 10.6.1.0 mask 255.255.255.0
 network 10.6.2.0 mask 255.255.255.0
 network 192.168.1.0
 neighbor 172.16.26.2 remote-as 100
 no auto-summary
!

All BGP neighborships are UP and Routers are advertising their respective prefixes into BGP.

R1#sh bgp all summary 
For address family: VPNv4 Unicast
BGP router identifier 172.16.0.1, local AS number 100
BGP table version is 4, main routing table version 4
3 network entries using 456 bytes of memory
3 path entries using 156 bytes of memory
5/2 BGP path/bestpath attribute entries using 660 bytes of memory
1 BGP AS-PATH entries using 24 bytes of memory
3 BGP extended community entries using 72 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 1368 total bytes of memory
BGP activity 6/3 prefixes, 6/3 paths, scan interval 60 secs

Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
172.16.0.2      4          100       8       4        4    0    0 00:01:15        0
172.16.13.3     4          333       6       3        4    0    0 00:01:15        2

R1#sh bgp vpnv4 unicast all 
BGP table version is 12, local router ID is 172.16.0.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, x best-external
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
Route Distinguisher: 333:3 (default for vrf AAA)
*> 10.3.1.0/24      172.16.13.3              0             0 333 i
*> 10.3.2.0/24      172.16.13.3              0             0 333 i
*> 172.16.13.0/24   0.0.0.0                  0         32768 ?
Route Distinguisher: 444:4
*>i10.4.1.0/24      172.16.0.2               0    100      0 444 i
*>i10.4.2.0/24      172.16.0.2               0    100      0 444 i
*>i172.16.24.0/24   172.16.0.2               0    100      0 ?
*>i192.168.1.0      172.16.0.2               0    100      0 444 i
Route Distinguisher: 666:6
*>i10.6.1.0/24      172.16.0.2               0    100      0 666 i
*>i10.6.2.0/24      172.16.0.2               0    100      0 666 i
*>i172.16.26.0/24   172.16.0.2               0    100      0 ?
*>i192.168.1.0      172.16.0.2               0    100      0 666 i



R2#sh bgp all summary 
For address family: VPNv4 Unicast
BGP router identifier 172.16.0.2, local AS number 100
BGP table version is 9, main routing table version 9
8 network entries using 1216 bytes of memory
8 path entries using 416 bytes of memory
6/4 BGP path/bestpath attribute entries using 792 bytes of memory
2 BGP AS-PATH entries using 48 bytes of memory
2 BGP extended community entries using 48 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 2520 total bytes of memory
BGP activity 22/14 prefixes, 22/14 paths, scan interval 60 secs

Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
172.16.0.1      4          100       6       9        9    0    0 00:01:40        0
172.16.24.4     4          444       6       6        9    0    0 00:01:45        3
172.16.26.6     4          666       6       6        9    0    0 00:01:45        3

R2#sh bgp vpnv4 unicast all 
BGP table version is 12, local router ID is 172.16.0.2
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, x best-external
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
Route Distinguisher: 333:3
*>i10.3.1.0/24      172.16.0.1               0    100      0 333 i
*>i10.3.2.0/24      172.16.0.1               0    100      0 333 i
*>i172.16.13.0/24   172.16.0.1               0    100      0 ?
Route Distinguisher: 444:4 (default for vrf BBB)
*> 10.4.1.0/24      172.16.24.4              0             0 444 i
*> 10.4.2.0/24      172.16.24.4              0             0 444 i
*> 172.16.24.0/24   0.0.0.0                  0         32768 ?
*> 192.168.1.0      172.16.24.4              0             0 444 i
Route Distinguisher: 666:6 (default for vrf CCC)
*> 10.6.1.0/24      172.16.26.6              0             0 666 i
*> 10.6.2.0/24      172.16.26.6              0             0 666 i
*> 172.16.26.0/24   0.0.0.0                  0         32768 ?
*> 192.168.1.0      172.16.26.6              0             0 666 i



R3#sh ip bgp summary 
BGP router identifier 172.16.13.3, local AS number 333
BGP table version is 29, main routing table version 29
3 network entries using 384 bytes of memory
3 path entries using 156 bytes of memory
2/2 BGP path/bestpath attribute entries using 248 bytes of memory
1 BGP AS-PATH 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 812 total bytes of memory
BGP activity 14/11 prefixes, 15/12 paths, scan interval 60 secs

Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
172.16.13.1     4          100      11      12       29    0    0 00:07:10        1

R3#sh ip bgp 
BGP table version is 29, local router ID is 172.16.13.3
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, x best-external
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*> 10.3.1.0/24      0.0.0.0                  0         32768 i
*> 10.3.2.0/24      0.0.0.0                  0         32768 i
r> 172.16.13.0/24   172.16.13.1              0             0 100 ?


R3#sh 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
       + - replicated route, % - next hop override

Gateway of last resort is not set

      10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
C        10.3.1.0/24 is directly connected, Loopback1
L        10.3.1.1/32 is directly connected, Loopback1
C        10.3.2.0/24 is directly connected, Loopback2
L        10.3.2.1/32 is directly connected, Loopback2
      172.16.0.0/16 is variably subnetted, 2 subnets, 2 masks
C        172.16.13.0/24 is directly connected, FastEthernet0/0
L        172.16.13.3/32 is directly connected, FastEthernet0/0



R4#sh ip bgp sum
BGP router identifier 172.16.24.4, local AS number 444
BGP table version is 31, main routing table version 31
4 network entries using 512 bytes of memory
4 path entries using 208 bytes of memory
2/2 BGP path/bestpath attribute entries using 248 bytes of memory
1 BGP AS-PATH 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 992 total bytes of memory
BGP activity 14/10 prefixes, 17/13 paths, scan interval 60 secs

Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
172.16.24.2     4          100      13      14       31    0    0 00:08:25        1

R4#sh ip bgp
BGP table version is 31, local router ID is 172.16.24.4
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, x best-external
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*> 10.4.1.0/24      0.0.0.0                  0         32768 i
*> 10.4.2.0/24      0.0.0.0                  0         32768 i
r> 172.16.24.0/24   172.16.24.2              0             0 100 ?
*> 192.168.1.0      0.0.0.0                  0         32768 i

R4#sh 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
       + - replicated route, % - next hop override

Gateway of last resort is not set

      10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
C        10.4.1.0/24 is directly connected, Loopback1
L        10.4.1.1/32 is directly connected, Loopback1
C        10.4.2.0/24 is directly connected, Loopback2
L        10.4.2.1/32 is directly connected, Loopback2
      172.16.0.0/16 is variably subnetted, 2 subnets, 2 masks
C        172.16.24.0/24 is directly connected, FastEthernet0/0
L        172.16.24.4/32 is directly connected, FastEthernet0/0
      192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks
C        192.168.1.0/24 is directly connected, Loopback192
L        192.168.1.1/32 is directly connected, Loopback192




R6#sh ip bgp sum
BGP router identifier 172.16.26.6, local AS number 666
BGP table version is 33, main routing table version 33
4 network entries using 512 bytes of memory
4 path entries using 208 bytes of memory
2/2 BGP path/bestpath attribute entries using 248 bytes of memory
1 BGP AS-PATH 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 992 total bytes of memory
BGP activity 13/9 prefixes, 18/14 paths, scan interval 60 secs

Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
172.16.26.2     4          100      14      14       33    0    0 00:09:03        1

R6#sh ip bgp
BGP table version is 33, local router ID is 172.16.26.6
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, x best-external
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*> 10.6.1.0/24      0.0.0.0                  0         32768 i
*> 10.6.2.0/24      0.0.0.0                  0         32768 i
r> 172.16.26.0/24   172.16.26.2              0             0 100 ?
*> 192.168.1.0      0.0.0.0                  0         32768 i

R6#sh 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
       + - replicated route, % - next hop override

Gateway of last resort is not set

      10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
C        10.6.1.0/24 is directly connected, Loopback1
L        10.6.1.1/32 is directly connected, Loopback1
C        10.6.2.0/24 is directly connected, Loopback2
L        10.6.2.1/32 is directly connected, Loopback2
      172.16.0.0/16 is variably subnetted, 2 subnets, 2 masks
C        172.16.26.0/24 is directly connected, FastEthernet0/0
L        172.16.26.6/32 is directly connected, FastEthernet0/0
      192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks
C        192.168.1.0/24 is directly connected, Loopback192
L        192.168.1.1/32 is directly connected, Loopback192

If we see the configuration on R2 ASN 444 prefixes are exported with route-target value 444:4. This is extended community attached to all prefixes exported into BGP table from VRF BBB.

We can verify the same with show output on R2 for any route of VRF BBB.

R2#sh bgp vpnv4 unicast vrf BBB 10.4.2.0
BGP routing table entry for 444:4:10.4.2.0/24, version 3
Paths: (1 available, best #1, table BBB)
  Advertised to update-groups:
     7         
  444
    172.16.24.4 from 172.16.24.4 (172.16.24.4)
      Origin IGP, metric 0, localpref 100, valid, external, best
      Extended Community: RT:444:4
      mpls labels in/out 34/nolabel

Let’s import prefix from ASN 444 into VRF AAA on router R1.

R1#conf t
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)#vrf definition AAA
R1(config-vrf)#address-family ipv4
R1(config-vrf-af)#route-target import ?
 ASN:nn or IP-address:nn Target VPN Extended Community

R1(config-vrf-af)#route-target import 444:4
R1(config-vrf-af)#end
R1#

We can see the prefixes with extended community value 444:4 are imported into VRF AAA now. And the same would be advertised to BGP Peer R3.

R1#sh bgp vpnv4 unicast all 
BGP table version is 16, local router ID is 172.16.0.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
 r RIB-failure, S Stale, m multipath, b backup-path, x best-external
Origin codes: i - IGP, e - EGP, ? - incomplete

 Network Next Hop Metric LocPrf Weight Path
Route Distinguisher: 333:3 (default for vrf AAA)
*> 10.3.1.0/24 172.16.13.3 0 0 333 i
*> 10.3.2.0/24 172.16.13.3 0 0 333 i
*>i10.4.1.0/24 172.16.0.2 0 100 0 444 i
*>i10.4.2.0/24 172.16.0.2 0 100 0 444 i
*> 172.16.13.0/24 0.0.0.0 0 32768 ?
*>i172.16.24.0/24 172.16.0.2 0 100 0 ?
*>i192.168.1.0 172.16.0.2 0 100 0 444 i
Route Distinguisher: 444:4
*>i10.4.1.0/24 172.16.0.2 0 100 0 444 i
*>i10.4.2.0/24 172.16.0.2 0 100 0 444 i
*>i172.16.24.0/24 172.16.0.2 0 100 0 ?
*>i192.168.1.0 172.16.0.2 0 100 0 444 i
Route Distinguisher: 666:6
*>i10.6.1.0/24 172.16.0.2 0 100 0 666 i
 Network Next Hop Metric LocPrf Weight Path
*>i10.6.2.0/24 172.16.0.2 0 100 0 666 i
*>i172.16.26.0/24 172.16.0.2 0 100 0 ?
*>i192.168.1.0 172.16.0.2 0 100 0 666 i

BGP Table and Route table on R3:

R3#sh ip bgp sum
BGP router identifier 172.16.13.3, local AS number 333
BGP table version is 33, main routing table version 33
7 network entries using 896 bytes of memory
7 path entries using 364 bytes of memory
4/4 BGP path/bestpath attribute entries using 496 bytes of memory
2 BGP AS-PATH entries using 48 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 1804 total bytes of memory
BGP activity 18/11 prefixes, 19/12 paths, scan interval 60 secs

Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
172.16.13.1     4          100      44      44       33    0    0 00:35:47        5

R3#sh ip bgp
BGP table version is 33, local router ID is 172.16.13.3
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, x best-external
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*> 10.3.1.0/24      0.0.0.0                  0         32768 i
*> 10.3.2.0/24      0.0.0.0                  0         32768 i
*> 10.4.1.0/24      172.16.13.1                            0 100 444 i
*> 10.4.2.0/24      172.16.13.1                            0 100 444 i
r> 172.16.13.0/24   172.16.13.1              0             0 100 ?
*> 172.16.24.0/24   172.16.13.1                            0 100 ?
*> 192.168.1.0      172.16.13.1                            0 100 444 i

R3#sh ip route bgp 
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
       + - replicated route, % - next hop override

Gateway of last resort is not set

      10.0.0.0/8 is variably subnetted, 6 subnets, 2 masks
B        10.4.1.0/24 [20/0] via 172.16.13.1, 00:02:43
B        10.4.2.0/24 [20/0] via 172.16.13.1, 00:02:43
      172.16.0.0/16 is variably subnetted, 3 subnets, 2 masks
B        172.16.24.0/24 [20/0] via 172.16.13.1, 00:02:43
B     192.168.1.0/24 [20/0] via 172.16.13.1, 00:02:43

But we are receiving more prefix (all prefix advertised by R4) than our requirement.
We can use route-map with import-map under VRF to filter prefix as per our requirement.

R1#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
R1(config)#ip prefix-list R4-SELECTIVE-PREFIX seq 5 permit 10.4.2.0/24
R1(config)#
R1(config)#route-map AAA-VRF-IMPORT permit 10
R1(config-route-map)#match ip address prefix-list R4-SELECTIVE-PREFIX
R1(config-route-map)#exit
R1(config)#
R1(config)#vrf definition AAA
R1(config-vrf)#address-family ipv4
R1(config-vrf-af)#import map AAA-VRF-IMPORT
R1(config-vrf-af)#end
R1#
R1#clear bgp vpnv4 unicast * soft

Let’s do the same for import prefix from VRF CCC.

R1#
R1#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
R1(config)#ip prefix-list R6-SELECTIVE-PREFIX seq 5 permit 10.6.1.0/24
R1(config)#
R1(config)#route-map AAA-VRF-IMPORT permit 20
R1(config-route-map)#match ip address prefix-list R6-SELECTIVE-PREFIX
R1(config-route-map)#
R1(config-route-map)#vrf definition AAA
R1(config-vrf)#address-family ipv4
R1(config-vrf-af)#route-target import 666:6
R1(config-vrf-af)#end
R1#
R1#clear bgp vpnv4 unicast * soft 
R1#

Verify BGP table for VRF AAA on R1. Now it has imported only specific routes which are permitted by route-map.

R1#sh bgp vpnv4 unicast vrf AAA 
BGP table version is 20, local router ID is 172.16.0.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, x best-external
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
Route Distinguisher: 333:3 (default for vrf AAA)
*> 10.3.1.0/24      172.16.13.3              0             0 333 i
*> 10.3.2.0/24      172.16.13.3              0             0 333 i
*>i10.4.2.0/24      172.16.0.2               0    100      0 444 i
*>i10.6.1.0/24      172.16.0.2               0    100      0 666 i
*> 172.16.13.0/24   0.0.0.0                  0         32768 ?

Verify BGP table and Routing table on R3:

R3#sh ip bgp
BGP table version is 37, local router ID is 172.16.13.3
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, x best-external
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*> 10.3.1.0/24      0.0.0.0                  0         32768 i
*> 10.3.2.0/24      0.0.0.0                  0         32768 i
*> 10.4.2.0/24      172.16.13.1                            0 100 444 i
*> 10.6.1.0/24      172.16.13.1                            0 100 666 i
r> 172.16.13.0/24   172.16.13.1              0             0 100 ?

R3#sh ip route bgp 
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
       + - replicated route, % - next hop override

Gateway of last resort is not set

      10.0.0.0/8 is variably subnetted, 6 subnets, 2 masks
B        10.4.2.0/24 [20/0] via 172.16.13.1, 00:17:51
B        10.6.1.0/24 [20/0] via 172.16.13.1, 00:02:51

We have the route to reach remote networks of R4 and R6. Can we ping them?

R3#ping 10.4.2.1 source 10.3.1.1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.4.2.1, timeout is 2 seconds:
Packet sent with a source address of 10.3.1.1 
.....
Success rate is 0 percent (0/5)

No, WHY?
Because R4 and R6 don’t have route for R3’s networks to sent traffic back to R3.

R4#sh ip route 10.3.1.0
% Subnet not in table

We have to import VRF AAA’s routes into VRF BBB and CCC to get end-to-end reachability for these networks.
Apply below configuration on R2:

R2#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
R2(config)#vrf definition BBB
R2(config-vrf)#address-family ipv4
R2(config-vrf-af)#route-target import 333:3
R2(config-vrf-af)#
R2(config-vrf-af)#vrf definition CCC
R2(config-vrf)#address-family ipv4
R2(config-vrf-af)#route-target import 333:3
R2(config-vrf-af)#end
R2#
R2#clear bgp vpnv4 unicast * soft 
R2#
R2#

R2 is showing prefixes of VRF AAA imported into vrf BBB and CCC.

R2#sh bgp vpnv4 unicast all         
BGP table version is 18, local router ID is 172.16.0.2
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, x best-external
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
Route Distinguisher: 333:3
*>i10.3.1.0/24      172.16.0.1               0    100      0 333 i
*>i10.3.2.0/24      172.16.0.1               0    100      0 333 i
*>i172.16.13.0/24   172.16.0.1               0    100      0 ?
Route Distinguisher: 444:4 (default for vrf BBB)
*>i10.3.1.0/24      172.16.0.1               0    100      0 333 i
*>i10.3.2.0/24      172.16.0.1               0    100      0 333 i
*> 10.4.1.0/24      172.16.24.4              0             0 444 i
*> 10.4.2.0/24      172.16.24.4              0             0 444 i
*>i172.16.13.0/24   172.16.0.1               0    100      0 ?
*> 172.16.24.0/24   0.0.0.0                  0         32768 ?
*> 192.168.1.0      172.16.24.4              0             0 444 i
Route Distinguisher: 666:6 (default for vrf CCC)
*>i10.3.1.0/24      172.16.0.1               0    100      0 333 i
*>i10.3.2.0/24      172.16.0.1               0    100      0 333 i
   Network          Next Hop            Metric LocPrf Weight Path
*> 10.6.1.0/24      172.16.26.6              0             0 666 i
*> 10.6.2.0/24      172.16.26.6              0             0 666 i
*>i172.16.13.0/24   172.16.0.1               0    100      0 ?
*> 172.16.26.0/24   0.0.0.0                  0         32768 ?
*> 192.168.1.0      172.16.26.6              0             0 666 i
R2#

Let’s verify BGP table and Route table of R4 and R6.

R4#sh ip bgp
BGP table version is 34, local router ID is 172.16.24.4
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, x best-external
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*> 10.3.1.0/24      172.16.24.2                            0 100 333 i
*> 10.3.2.0/24      172.16.24.2                            0 100 333 i
*> 10.4.1.0/24      0.0.0.0                  0         32768 i
*> 10.4.2.0/24      0.0.0.0                  0         32768 i
*> 172.16.13.0/24   172.16.24.2                            0 100 ?
r> 172.16.24.0/24   172.16.24.2              0             0 100 ?
*> 192.168.1.0      0.0.0.0                  0         32768 i
R4#sh ip route bgp
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
       + - replicated route, % - next hop override

Gateway of last resort is not set

      10.0.0.0/8 is variably subnetted, 6 subnets, 2 masks
B        10.3.1.0/24 [20/0] via 172.16.24.2, 00:01:59
B        10.3.2.0/24 [20/0] via 172.16.24.2, 00:01:59
      172.16.0.0/16 is variably subnetted, 3 subnets, 2 masks
B        172.16.13.0/24 [20/0] via 172.16.24.2, 00:01:59
R4#sh ip route 10.3.1.0
Routing entry for 10.3.1.0/24
  Known via "bgp 444", distance 20, metric 0
  Tag 100, type external
  Last update from 172.16.24.2 00:02:05 ago
  Routing Descriptor Blocks:
  * 172.16.24.2, from 172.16.24.2, 00:02:05 ago
      Route metric is 0, traffic share count is 1
      AS Hops 2
      Route tag 100
      MPLS label: none
R4#


R6#sh ip bgp
BGP table version is 36, local router ID is 172.16.26.6
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, x best-external
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*> 10.3.1.0/24      172.16.26.2                            0 100 333 i
*> 10.3.2.0/24      172.16.26.2                            0 100 333 i
*> 10.6.1.0/24      0.0.0.0                  0         32768 i
*> 10.6.2.0/24      0.0.0.0                  0         32768 i
*> 172.16.13.0/24   172.16.26.2                            0 100 ?
r> 172.16.26.0/24   172.16.26.2              0             0 100 ?
*> 192.168.1.0      0.0.0.0                  0         32768 i
R6#
R6#sh ip route bgp
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
       + - replicated route, % - next hop override

Gateway of last resort is not set

      10.0.0.0/8 is variably subnetted, 6 subnets, 2 masks
B        10.3.1.0/24 [20/0] via 172.16.26.2, 00:02:29
B        10.3.2.0/24 [20/0] via 172.16.26.2, 00:02:29
      172.16.0.0/16 is variably subnetted, 3 subnets, 2 masks
B        172.16.13.0/24 [20/0] via 172.16.26.2, 00:02:29
R6#

Now check end-to-end connectivity with Ping from R3 to R4 and R6 networks.

R3#ping 10.4.2.1 source 10.3.1.1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.4.2.1, timeout is 2 seconds:
Packet sent with a source address of 10.3.1.1 
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 32/51/76 ms

R3#ping 10.6.1.1 source 10.3.1.1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.6.1.1, timeout is 2 seconds:
Packet sent with a source address of 10.3.1.1 
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 44/52/64 ms

Everything looks fine so far.

We got another requirement. On Router R1, VRF AAA has to import prefix 192.168.1.0/24 from VRF BBB.

Currently we are using below prefix-list and route-map:

R1#sh run | s prefix-list|route-map
ip prefix-list R4-SELECTIVE-PREFIX seq 5 permit 10.4.2.0/24
ip prefix-list R6-SELECTIVE-PREFIX seq 5 permit 10.6.1.0/24
route-map AAA-VRF-IMPORT permit 10
 match ip address prefix-list R4-SELECTIVE-PREFIX
route-map AAA-VRF-IMPORT permit 20
 match ip address prefix-list R6-SELECTIVE-PREFIX

If we create another prefix list entry to permit 192.168.1.0/24, We should be all set.

R1#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
R1(config)#ip prefix-list R4-SELECTIVE-PREFIX seq 10 permit 192.168.1.0/24
R1(config)#end
R1#

Let’s verify routing table on R3. We have route for 192.168.1.0/24 now.

R3#sh ip route bgp 
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
       + - replicated route, % - next hop override

Gateway of last resort is not set

      10.0.0.0/8 is variably subnetted, 6 subnets, 2 masks
B        10.4.2.0/24 [20/0] via 172.16.13.1, 00:41:07
B        10.6.1.0/24 [20/0] via 172.16.13.1, 00:26:07
B     192.168.1.0/24 [20/0] via 172.16.13.1, 00:00:06

And we can ping remote network also.

R3#ping 192.168.1.1 source 10.3.1.1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.1.1, timeout is 2 seconds:
Packet sent with a source address of 10.3.1.1 
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 16/39/56 ms

Everything looks fine.

Let’s goto Router R4 and shutdown interface Loopback 192 which is used for network 192.168.1.0/24

R4#sh run int l192
Building configuration...

Current configuration : 67 bytes
!
interface Loopback192
 ip address 192.168.1.1 255.255.255.0
end

R4#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
R4(config)#int l192
R4(config-if)#shut
R4(config-if)#
R4(config-if)#
*Jun  4 19:29:03.474: %LINK-5-CHANGED: Interface Loopback192, changed state to administratively down
*Jun  4 19:29:04.474: %LINEPROTO-5-UPDOWN: Line protocol on Interface Loopback192, changed state to down
R4(config-if)#

Now goto Router R3 and try to ping 192.168.1.1 again. It should not be working, right?
But it can still ping it 🙂

Let’s see who is this 192.168.1.1 device.

R3#192.168.1.1
Trying 192.168.1.1 ... Open


User Access Verification

Password: 
R6#

Hmm..we are receiving 192.168.1.0/24 prefix from R6(VRF CCC).

Let’s enable interface loopback192 on R4.

R4(config-if)#no shut
R4(config-if)#end
R4#
*Jun  4 19:31:05.626: %LINK-3-UPDOWN: Interface Loopback192, changed state to up
*Jun  4 19:31:06.490: %SYS-5-CONFIG_I: Configured from console by console
R4#
*Jun  4 19:31:06.626: %LINEPROTO-5-UPDOWN: Line protocol on Interface Loopback192, changed state to up
R4#

Let’s see what is happening on Router R1 for importing routes from other VRFs.

R1#sh bgp vpnv4 unicast all    
BGP table version is 24, local router ID is 172.16.0.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, x best-external
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
Route Distinguisher: 333:3 (default for vrf AAA)
*> 10.3.1.0/24      172.16.13.3              0             0 333 i
*> 10.3.2.0/24      172.16.13.3              0             0 333 i
*>i10.4.2.0/24      172.16.0.2               0    100      0 444 i
*>i10.6.1.0/24      172.16.0.2               0    100      0 666 i
*> 172.16.13.0/24   0.0.0.0                  0         32768 ?
* i192.168.1.0      172.16.0.2               0    100      0 444 i
*>i                 172.16.0.2               0    100      0 666 i
Route Distinguisher: 444:4
*>i10.4.1.0/24      172.16.0.2               0    100      0 444 i
*>i10.4.2.0/24      172.16.0.2               0    100      0 444 i
*>i172.16.24.0/24   172.16.0.2               0    100      0 ?
*>i192.168.1.0      172.16.0.2               0    100      0 444 i
Route Distinguisher: 666:6
*>i10.6.1.0/24      172.16.0.2               0    100      0 666 i
   Network          Next Hop            Metric LocPrf Weight Path
*>i10.6.2.0/24      172.16.0.2               0    100      0 666 i
*>i172.16.26.0/24   172.16.0.2               0    100      0 ?
*>i192.168.1.0      172.16.0.2               0    100      0 666 i
R1#

It has imported this route from two different VRFs (BBB and CCC)

R1#sh bgp vpnv4 unicast vrf AAA 192.168.1.0
BGP routing table entry for 333:3:192.168.1.0/24, version 23
Paths: (2 available, best #2, table AAA)
  Advertised to update-groups:
     5         
  444, imported path from 444:4:192.168.1.0/24
    172.16.0.2 (metric 2) from 172.16.0.2 (172.16.0.2)
      Origin IGP, metric 0, localpref 100, valid, internal
      Extended Community: RT:444:4
      mpls labels in/out nolabel/21
  666, imported path from 666:6:192.168.1.0/24
    172.16.0.2 (metric 2) from 172.16.0.2 (172.16.0.2)
      Origin IGP, metric 0, localpref 100, valid, internal, best
      Extended Community: RT:666:6
      mpls labels in/out nolabel/38

This is not our requirement. We want to import it only from VRF BBB.

We have to match prefix along with extended community value to achieve this goal.

Create extended-community list and match it inside route-map.

R1#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
R1(config)#ip extcommunity-list standard FROM-R4 permit rt 444:4
R1(config)#ip extcommunity-list standard FROM-R6 permit rt 666:6
R1(config)#
R1(config)#route-map AAA-VRF-IMPORT permit 10
R1(config-route-map)#match extcommunity FROM-R4
R1(config-route-map)#route-map AAA-VRF-IMPORT permit 20
R1(config-route-map)#match extcommunity FROM-R6        
R1(config-route-map)#end
R1#

We have this configuration now:

R1#sh run | s prefix|extcommunity-list|route-map
ip extcommunity-list standard FROM-R4 permit rt 444:4
ip extcommunity-list standard FROM-R6 permit rt 666:6
ip prefix-list R4-SELECTIVE-PREFIX seq 5 permit 10.4.2.0/24
ip prefix-list R4-SELECTIVE-PREFIX seq 10 permit 192.168.1.0/24
ip prefix-list R6-SELECTIVE-PREFIX seq 5 permit 10.6.1.0/24
route-map AAA-VRF-IMPORT permit 10
 match ip address prefix-list R4-SELECTIVE-PREFIX
 match extcommunity FROM-R4
route-map AAA-VRF-IMPORT permit 20
 match ip address prefix-list R6-SELECTIVE-PREFIX
 match extcommunity FROM-R6
R1#

Here route-map would use Boolean AND logic and permit prefix if it is matched by BOTH conditions, prefix-list and extended-community value.

Route-map sequence #10 will match prefixes 10.4.2.0/24 and 192.168.1.0/24 if they have RT extended-community value 444:4 only.

Similarily Route-map sequence #20 will match prefixes 10.6.1.0/24 if it has RT extended-community value 666:6 only.

Verify VRF AAA BGP table now on Router R1.

R1#sh bgp vpnv4 unicast vrf AAA
BGP table version is 25, local router ID is 172.16.0.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, x best-external
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
Route Distinguisher: 333:3 (default for vrf AAA)
*> 10.3.1.0/24      172.16.13.3              0             0 333 i
*> 10.3.2.0/24      172.16.13.3              0             0 333 i
*>i10.4.2.0/24      172.16.0.2               0    100      0 444 i
*>i10.6.1.0/24      172.16.0.2               0    100      0 666 i
*> 172.16.13.0/24   0.0.0.0                  0         32768 ?
*>i192.168.1.0      172.16.0.2               0    100      0 444 i

R1#sh bgp vpnv4 unicast vrf AAA 192.168.1.0
BGP routing table entry for 333:3:192.168.1.0/24, version 25
Paths: (1 available, best #1, table AAA)
  Advertised to update-groups:
     5         
  444, imported path from 444:4:192.168.1.0/24
    172.16.0.2 (metric 2) from 172.16.0.2 (172.16.0.2)
      Origin IGP, metric 0, localpref 100, valid, internal, best
      Extended Community: RT:444:4
      mpls labels in/out nolabel/21

Verify BGP table, reachability from R3 for all remote networks.

R3#sh ip bgp
BGP table version is 40, local router ID is 172.16.13.3
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, x best-external
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*> 10.3.1.0/24      0.0.0.0                  0         32768 i
*> 10.3.2.0/24      0.0.0.0                  0         32768 i
*> 10.4.2.0/24      172.16.13.1                            0 100 444 i
*> 10.6.1.0/24      172.16.13.1                            0 100 666 i
r> 172.16.13.0/24   172.16.13.1              0             0 100 ?
*> 192.168.1.0      172.16.13.1                            0 100 444 i


R3#sh ip route bgp
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
       + - replicated route, % - next hop override

Gateway of last resort is not set

      10.0.0.0/8 is variably subnetted, 6 subnets, 2 masks
B        10.4.2.0/24 [20/0] via 172.16.13.1, 01:02:20
B        10.6.1.0/24 [20/0] via 172.16.13.1, 00:47:20
B     192.168.1.0/24 [20/0] via 172.16.13.1, 00:08:19


R3#ping 10.4.2.1 source 10.3.1.1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.4.2.1, timeout is 2 seconds:
Packet sent with a source address of 10.3.1.1 
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 40/48/60 ms

R3#ping 10.6.1.1 source 10.3.1.1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.6.1.1, timeout is 2 seconds:
Packet sent with a source address of 10.3.1.1 
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 40/49/64 ms

R3#ping 192.168.1.1 source 10.3.1.1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.1.1, timeout is 2 seconds:
Packet sent with a source address of 10.3.1.1 
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 24/45/72 ms

Final Configuration on R1 and R2.

R1:

vrf definition AAA
rd 333:3
!
address-family ipv4
import map AAA-VRF-IMPORT
route-target export 333:3
route-target import 333:3
route-target import 444:4
route-target import 666:6
exit-address-family
!
interface Loopback0
ip address 172.16.0.1 255.255.255.255
ip ospf 1 area 0
!
interface FastEthernet0/0
ip address 172.16.12.1 255.255.255.0
ip ospf network point-to-point
ip ospf 1 area 0
mpls ip
!
interface FastEthernet1/0
vrf forwarding AAA
ip address 172.16.13.1 255.255.255.0
speed 100
duplex full
!
router ospf 1
log-adjacency-changes
!
router bgp 100
bgp router-id 172.16.0.1
no bgp default ipv4-unicast
no bgp default route-target filter
bgp log-neighbor-changes
neighbor 172.16.0.2 remote-as 100
neighbor 172.16.0.2 update-source Loopback0
!
address-family ipv4
no synchronization
no auto-summary
exit-address-family
!
address-family vpnv4
neighbor 172.16.0.2 activate
neighbor 172.16.0.2 send-community extended
exit-address-family
!
address-family ipv4 vrf AAA
no synchronization
redistribute connected
neighbor 172.16.13.3 remote-as 333
neighbor 172.16.13.3 activate
exit-address-family
!
!
ip extcommunity-list standard FROM-R4 permit rt 444:4
ip extcommunity-list standard FROM-R6 permit rt 666:6
!
ip prefix-list R4-SELECTIVE-PREFIX seq 5 permit 10.4.2.0/24
ip prefix-list R4-SELECTIVE-PREFIX seq 10 permit 192.168.1.0/24
!
ip prefix-list R6-SELECTIVE-PREFIX seq 5 permit 10.6.1.0/24
!
route-map AAA-VRF-IMPORT permit 10
match ip address prefix-list R4-SELECTIVE-PREFIX
match extcommunity FROM-R4
!
route-map AAA-VRF-IMPORT permit 20
match ip address prefix-list R6-SELECTIVE-PREFIX
match extcommunity FROM-R6
!

R2:

vrf definition BBB
rd 444:4
!
address-family ipv4
route-target export 444:4
route-target import 444:4
route-target import 333:3
exit-address-family
!
vrf definition CCC
rd 666:6
!
address-family ipv4
route-target export 666:6
route-target import 666:6
route-target import 333:3
exit-address-family
!
interface Loopback0
ip address 172.16.0.2 255.255.255.255
ip ospf 1 area 0
!
interface FastEthernet0/0
ip address 172.16.12.2 255.255.255.0
ip ospf network point-to-point
ip ospf 1 area 0
mpls ip
!
interface FastEthernet1/0
vrf forwarding BBB
ip address 172.16.24.2 255.255.255.0
!
interface FastEthernet1/1
vrf forwarding CCC
ip address 172.16.26.2 255.255.255.0
!
router ospf 1
log-adjacency-changes
!
router bgp 100
bgp router-id 172.16.0.2
no bgp default ipv4-unicast
no bgp default route-target filter
bgp log-neighbor-changes
neighbor 172.16.0.1 remote-as 100
neighbor 172.16.0.1 update-source Loopback0
!
address-family ipv4
no synchronization
no auto-summary
exit-address-family
!
address-family vpnv4
neighbor 172.16.0.1 activate
neighbor 172.16.0.1 send-community extended
exit-address-family
!
address-family ipv4 vrf BBB
no synchronization
redistribute connected
neighbor 172.16.24.4 remote-as 444
neighbor 172.16.24.4 activate
exit-address-family
!
address-family ipv4 vrf CCC
no synchronization
redistribute connected
neighbor 172.16.26.6 remote-as 666
neighbor 172.16.26.6 activate
exit-address-family

Amolak Networks

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Monthly Archives: June 2015

OSPF Route Summarization

1. Inter-Area Route Summarization

2. External Route Summarization

Route Leak between VRFs with Import MAP