If BGP PEER is in idle state, then it could be due to physical CONNECTIVITY failure or the neighbor is not DEFINED properly with respective AS. In CONNECT state, BGP tries to establish a TCP session over port number 179; if it fails to establish the connection, then it goes to active state, where it tries again to establish a TCP connection. By using “debug ip bgp” and “debug ip tcp transactions” commands, we can LEARN the exact cause of TCP connection failure. Lack of the “update-source” or “ebgp-multihop” command can also be a reason of neighbor active state.

If BGP peer is in idle state, then it could be due to physical connectivity failure or the neighbor is not defined properly with respective AS. In connect state, BGP tries to establish a TCP session over port number 179; if it fails to establish the connection, then it goes to active state, where it tries again to establish a TCP connection. By using “debug ip bgp” and “debug ip tcp transactions” commands, we can learn the exact cause of TCP connection failure. Lack of the “update-source” or “ebgp-multihop” command can also be a reason of neighbor active state.