BGP Peering States
The command show ip bgp neighbors shows a list of peers, and the status
of their peering session. This status can include the following states:
�¡ Idle.No peering; router is looking for neighbor. Idle (admin) means
that the neighbor relationship has been administratively shut down.
�¡ Connect.TCP handshake completed.
�¡ OpenSent, or Active.An open message was sent to try to establish
the peering.
�¡ OpenConfirm.Router has received a reply to the open message.
�¡ Established.Routers have a BGP peering session. This is the desired
state.
You can troubleshoot session establishment with debug commands. Use
debug ip bgp events or debug ip bgp ipv4 unicast (in IOS versions 12.4
and up) to see where the process fails. Some common failure causes include
AS number misconfiguration, neighbor IP address misconfiguration, neighbor
with no neighbor statement for your router, and neighbor with no route
to the source address of your router�fs BGP messages.