Troubleshooting guide

Troubleshooting BGP
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Missing Network Destination Advertisement
When BGP routers do not advertise routes, routing updates from those routers do not
contain information about certain network destinations that should be advertised.
Follow these steps to solve BGP advertising routing problems:
1. To view the router configuration, use the show running-config command in
Privileged EXEC mode.
2. Ensure that the network command entered in Router Configuration mode is
specified for every network that the BGP router should advertise (these networks
need not be directly connected). For example, if the BGP router needs to
advertise networks 10.168.52.0 and 10.168.0.0, enter the following commands to
have the router include those networks in its routing updates, as shown in the
series of commands below:
RDN(config)#router bgp
RDN(config-bgp)#network 10.168.52.0
RDN(config-bgp)#network 10.168.0.0
Handling BGP Peer Misconfigurations
Follow these steps to find and resolve a misconfigured or missing configuration for
BGP peers:
1. To verify that all the required BGP peers are configured with the correct IP
addresses and AS numbers, use the show ip bgp neighbors command in
Privileged EXEC mode, as shown in the following example:
RDN#show ip bgp neighbors
2. If some BGP peer routers are misconfigured or are not configured, configure
them with the proper IP addresses and AS numbers.
To add an entry to the BGP neighbor table, use the neighbor remote-as
command in Router Interface Configuration mode, as shown in the following
example. The BGP neighbor table identifies a router as a BGP peer and maps its
IP address to a specific AS.