BGP Session Timeout

Pascal Gloor pascal.gloor at
Tue May 1 07:58:23 UTC 2007

> Is it likely that BGP times out before underlying IP topology  
> reconvergences
> after a link/node failure? Do service providers ever set such low  
> values of
> BGP timeouts that BGP timeout will occur?
> If not, what else may cause a BGP session to time out?

Depending on your hardware, you can trigger your BGP and IGP to shut  
sessions when the peer is gone.

On some cisco, you can have BFD (Bidirectional Forwarding Detection).  
you have to enable this on both sides. If BFD notices the peer is  
down, it will notify OSPF,BGP,... (if configured so).

for example:

interface GigabitEthernet0/0
  ip address
  bfd neighbor
  bfd interval 250 min_rx 250 multiplier 3
  ip ospf bfd

This will send a BFD packet every 250ms, expect one every 250ms and  
if 3 packets are missed (after 750ms) it will tell OSPF to shut any  
session towards (or routed via for the BGP case).

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