Friday, April 1, 2011

Lab 93 - IBGP Route-Reflector

Prerequisites: CCNP level skills.


Use the Lab 92 configuration.

Pic. 1 - Topology Diagram.
Icons designed by: Andrzej Szoblik -

Task 1
Ensure reachability between and

Lab Solution

Task 1
Ensure reachability between and

Since IBGP Split-Horizon rule forbids to advertise prefixes learned from IBGP peer to another IBGP peer, R1 does not forward to R5 and to R2. There are two solutions to this problem:
  • Route-Reflector configuration on R1 (disabling IBGP Split-Horizon)
  • Configure BGP Confederations
Pic. 2 - R3's BGP Table.
R3 does not receive from R1.

Pic. 3 - R4's BGP Table.
R4 does not receive from R1.

R1 Configuration:
router bgp 134
 no synchronization
 bgp router-id
 bgp log-neighbor-changes
 network mask
 neighbor remote-as 134
 neighbor route-reflector-client
 neighbor remote-as 134
 neighbor route-reflector-client
 no auto-summary

Pic. 4 - Ping Test.

The rules with route-reflectors are as in below:

Pic.5 - Route-Reflector-Rules

Prefixes are getting propagated this time since R1 receives them from route-reflector-clients and passes them to other clients.

Pic. 6 - Prefixes from Route-Reflector-Clients.

Once Route-Reflectors are configured, two additional attributes begin to play a major role when Route-Reflector Clusters are in place (multiple route-reflectors for redundancy purposes).

Pic. 7 - Route Originator and Cluster List.
If the design is not done correctly a router can receive the prefix it originated itself. The originator address will help discover this and reject the update. Also, if route-reflector receives the prefix with its own address in the cluster list it will ignore it.