You might have been there before: the BGP neighbor becomes reachable after you fix a fault in the network, but the BGP session takes “forever” to be established (actually, the hold off is less than a minute, but time is running slower when you are waiting for the network to recover). However, when testing the BGP fast peering session deactivation, I made an interesting discovery: the restart time is improved as well; as soon as the path to the BGP neighbor appears in the IP routing table, the BGP session is established. The debugging printouts from my router are included below (I've used neighbor 10.0.3.3 fall-over configuration command):
03:28:42: RT: add 10.0.3.3/32 via 10.2.0.2, ospf metric [110/75]
03:28:42: RT: NET-RED 10.0.3.3/32
03:28:44: RT: Try lookup less specific 10.0.3.3/32, default 1
03:28:44: RT: Found subnet on less specific 10.0.3.3/32
03:28:44: %BGP-5-ADJCHANGE: neighbor 10.0.3.3 UpPosted to Cisco IOS Hints and Tricks by Ivan Pepelnjak
© Copyright Ivan Pepelnjak
