Cisco BGP-4 Command and Configuration Handbook

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.

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.