BGP Session Timeout

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One could also presume that BFD should also be considered
dangerous, if enabled.

- - ferg

Is it likely that BGP times out before underlying IP topology
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).