16-1 debug ip bgp

Syntax Description: This command has no arguments.

Purpose: Use to debug the formation of the BGP neighbor relationship.

Cisco IOS Software Release: 10.0

Configuration Example

In Figure 16-1, Router B has been configured with the wrong AS number for Router A.

Figure 16-1. Use debug ip bgp to Determine Configuration Errors

 Router A  router bgp 1   neighbor 172.17.1.1 remote-as 2   ___________________________________________________________________________  Router B  router bgp 2   neighbor 172.17.1.2 remote-as 1  

Use debug ip bgp to identify the problem with the formation of the neighbor relationship between Routers A and B:

 rtrB#  debug ip bgp  rtrB#  clear ip bgp *  1d03h: BGP: 172.17.1.2 went from Idle to Active 1d03h: BGP: 172.17.1.2 open active, delay 5492ms 1d03h: BGP: 172.17.1.2 open active, local address 172.17.1.1 1d03h: BGP: 172.17.1.2 went from Active to OpenSent 1d03h: BGP: 172.17.1.2 sending OPEN, version 4, my as: 2 1d03h: BGP: 172.17.1.2 send message type 1, length (incl. header) 41 1d03h: BGP: 172.17.1.2 rcv message type 1, length (excl. header) 10 1d03h: BGP: 172.17.1.2 rcv OPEN, version 4 1d03h: BGP: 172.17.1.2 rcv OPEN w/ OPTION parameter len: 0  1d03h: BGP: 172.17.1.2 bad OPEN, remote AS is 1, expected 2  1d03h: BGP: 172.17.1.2 went from OpenSent to Closing  1d03h: BGP: 172.17.1.2 sending NOTIFICATION 2/2 (peer in wrong AS) 2 bytes 0001  1d03h: BGP: 172.17.1.2 local error close, erroneous BGP update received 1d03h: BGP: 172.17.1.2 went from Closing to Idle 1d03h: BGP: 172.17.1.2 closing 

Correct the remote AS number in the neighbor statement on Router B, but use an incorrect IP address for Router A:

 Router B  router bgp 2   neighbor 172.17.1.3 remote-as 1  

Clear the connection and observe the debug output:

 rtrB#  debug ip bgp  rtrB#  clear ip bgp *  1d04h: BGP: 172.17.1.3 open active, local address 172.17.1.1  1d04h: BGP: 172.17.1.3 open failed: Connection timed out; remote host not responding