Tuesday, May 3, 2011

Lab 119 - BGP Conditional Route Injection

Prerequisites: CCNP level skills.

Note!
Topology from Lab 118.

Topology

Pic. 1 - Topology Diagram.
Icons designed by: Andrzej Szoblik - http://www.newo.pl

Task 1
On R4 advertise into BGP two summary prefixes representing subnets 40.x.x.x/16 and 44.4.x.x/19.

Task 2
Configure R2 in such a way that apart from the two aggregates it BGP table also injects 40.2.0.0/16.

Solution

Task 1
On R4 advertise into BGP two summary prefixes representing subnets 40.x.x.x/16 and 44.4.x.x/19.

R4 Configuration:
!
router bgp 40
 no synchronization
 bgp router-id 172.16.104.4
 bgp log-neighbor-changes
 network 172.16.104.0 mask 255.255.255.0
 network 172.16.144.0 mask 255.255.255.0
 aggregate-address 44.4.0.0 255.255.128.0 summary-only
 aggregate-address 40.0.0.0 255.252.0.0 summary-only
 redistribute connected route-map CONN_TO_BGP
 neighbor 10.1.14.1 remote-as 10
 neighbor 10.1.24.2 remote-as 20
 no auto-summary
!

Verification:
Pic. 2 - R2's BGP table (aggregates).


Task 2
Configure R2 in such a way that apart from the two aggregates it BGP table also injects 40.2.0.0/16.

R2 Configuration:
!
ip prefix-list ADV_ROUTER seq 5 permit 10.1.24.4/32
!
ip prefix-list EXIST seq 5 permit 40.0.0.0/14
!
ip prefix-list INJECT_PFX seq 5 permit 40.2.0.0/16
!
route-map TO_BE_INJECTED permit 10
 set ip address prefix-list INJECT_PFX
!
route-map MUST_EXIST permit 10
 match ip address prefix-list EXIST
 match ip route-source prefix-list ADV_ROUTER
!
router bgp 20
 no synchronization
 bgp router-id 172.16.102.2
 bgp log-neighbor-changes
 bgp inject-map TO_BE_INJECTED exist-map MUST_EXIST
 network 172.16.102.0 mask 255.255.255.0
 neighbor 10.1.23.3 remote-as 30
 neighbor 10.1.24.4 remote-as 40
 no auto-summary
!

Verification:
Pic. 3 - R2 Injects the Prefix into BGP.

Notice!
After around a minute, the prefix gets injected. The route-map which specifies the condition for the prefix injection (here: EXIST) must refer to the advertising router's address. Otherwise the conditional route injections does not seem to work.