3-5 bgp client-to-client reflection

3-5 bgp client-to-client reflection

Syntax Description:

This command has no arguments.

Purpose: When a router is configured as a route reflector, client-to-client reflection is enabled by default. If the route reflector's clients are fully meshed, client-to-client reflection can be disabled on the route reflector using the no form of the command.

Cisco IOS Software Release: 11.1

Configuration Example: Route Reflectors and Peer Groups

An obvious question is why use a route reflector if the clients have a full IBGP mesh? If client-to-client reflection is enabled, the clients cannot be part of a peer group. Figure 3-5 demonstrates a situation in which we want to scale the IBGP connections using route reflectors, but we also want Routers A, B, and C to be part of the same peer group . Therefore, client-to-client reflection needs to be disabled on Router B. The total number of IBGP connections is still reduced, even though the clients are fully meshed. Routers B and D need to be configured as route reflectors. If B and D were not route reflectors, a full mesh would be required between all five routers. A route reflector is set up by configuring Routers A and C as route reflector clients on Router B. But because the clients are fully meshed, route reflection can be disabled on Router B.

Figure 3-5. Route Reflectors and Peer Groups

 Router A  interface Serial0   ip address 193.16.0.2 255.255.255.252    !   router eigrp 1   network 193.16.0.0   no auto-summary   !   router bgp 1   neighbor 193.16.0.1 remote-as 1   ___________________________________________________________________________  Router B  interface Ethernet1/0   ip address 172.16.0.1 255.255.255.252   !   interface Ethernet1/2   ip address 172.16.0.17 255.255.255.252   !   interface Serial2/0   ip address 193.16.0.1 255.255.255.252   clockrate 64000   !   router eigrp 1   network 172.16.0.0   network 193.16.0.0   no auto-summary   !   router bgp 1   neighbor 172.16.0.18 remote-as 1   no bgp client-to-client reflection   neighbor group1 peer-group   neighbor group1 remote-as 1    neighbor group1 route-reflector-client    neighbor 172.16.0.2 peer-group group1   neighbor 193.16.0.2 peer-group group1   ___________________________________________________________________________  Router C  interface Ethernet1/0   ip address 172.16.0.2 255.255.255.252   !   router eigrp 1   network 172.16.0.0   no auto-summary   !   router bgp 1   neighbor 172.16.0.1 remote-as 1   neighbor 193.16.0.2 remote-as 1   ___________________________________________________________________________  Router D  interface Ethernet1/0   ip address 172.16.0.14 255.255.255.252   !   interface Ethernet1/2   ip address 172.16.0.18 255.255.255.252   !   router eigrp 1   network 172.16.0.0   network 193.16.0.0   no auto-summary   !   router bgp 1   neighbor 172.16.0.13 remote-as 1    neighbor 172.16.0.13 route-reflector-client    neighbor 172.16.0.17 remote-as 1   ___________________________________________________________________________  Router E  interface Ethernet2/1   ip address 172.16.0.13 255.255.255.252   !   router eigrp 1   network 172.16.0.0   no auto-summary   !   router bgp 1   neighbor 172.16.0.14 remote-as 1  

Verification

Verify that the neighbors have been configured in the proper peer group and that the route reflector is enabled:

 rtrB#  show ip bgp n  BGP neighbor is 172.16.0.2,  remote AS 1, internal link  Member of peer-group group1 for session parameters   BGP version 4, remote router ID 172.16.88.3   BGP state = Established, up for 00:11:33   Last read 00:00:34, hold time is 180, keepalive interval is 60 seconds   Neighbor capabilities:     Route refresh: advertised and received     Address family IPv4 Unicast: advertised and received   Received 115 messages, 0 notifications, 0 in queue   Sent 110 messages, 0 notifications, 0 in queue   Route refresh request: received 0, sent 0   Minimum time between advertisement runs is 5 seconds  For address family: IPv4 Unicast   BGP table version 4, neighbor version 4   Index 1, Offset 0, Mask 0x2  Route-Reflector Client   group1 peer-group member  BGP neighbor is 193.16.0.2,  remote AS 1, internal link  Member of peer-group group1 for session parameters   BGP version 4, remote router ID 193.16.0.2   BGP state = Established, up for 00:12:07   Last read 00:00:08, hold time is 180, keepalive interval is 60 seconds   Neighbor capabilities:     Route refresh: advertised     Address family IPv4 Unicast: advertised and received   Received 108 messages, 0 notifications, 0 in queue   Sent 108 messages, 0 notifications, 0 in queue   Route refresh request: received 0, sent 0   Minimum time between advertisement runs is 5 seconds  For address family: IPv4 Unicast   BGP table version 4, neighbor version 4   Index 1, Offset 0, Mask 0x2  Route-Reflector Client   group1 peer-group member  0 accepted prefixes consume 0 bytes   Prefix advertised 0, suppressed 0, withdrawn 0 

Troubleshooting

Step 1. Verify that the BGP neighbors are in the Established state using the show ip bgp neighbors command.

If the neighbor relationship is not in the Established state, see section 8-23. For IBGP and loopbacks, see section 8-33.

Step 2. Verify that the IBGP neighbors have been configured as route reflector clients and that they are in the proper peer group using the show ip bgp neighbors command.

Step 3. Verify that BGP client-to-client reflection has been disabled.