[96328] in North American Network Operators' Group
Re: BGP Session Timeout
daemon@ATHENA.MIT.EDU (Fergie)
Tue May 1 04:13:44 2007
From: "Fergie" <fergdawg@netzero.net>
Date: Tue, 1 May 2007 08:11:15 GMT
To: pascal.gloor@spale.com
Cc: msaqib@gmail.com, nanog@merit.edu
Errors-To: owner-nanog@merit.edu
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One could also presume that BFD should also be considered
dangerous, if enabled.
- - ferg
- -- Pascal Gloor <pascal.gloor@spale.com> wrote:
> 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 10.1.1.1 255.255.255.252
bfd neighbor 10.1.1.2
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 10.1.1.2 (or routed via 10.1.1.2 for the BGP case).
Pascal
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--
"Fergie", a.k.a. Paul Ferguson
Engineering Architecture for the Internet
fergdawg(at)netzero.net
ferg's tech blog: http://fergdawg.blogspot.com/
