Re: Nasty iBGP design issue...

From: Gert Doering (gert@greenie.muc.de)
Date: Tue Jul 03 2001 - 10:12:48 EDT


Hi,

On Tue, Jul 03, 2001 at 02:20:25PM +0100, Pegg Damon wrote:
> I have a serious problem with failover speeds within iBGP for dual-homed
> customers, from a carrier's perspective. [..]

Depending on *what* fails, you can speed it up significantly by setting
the BGP keepalive timers to a lower value in your neigbour configuration
- something like "neigh 1.2.3.4 timers 1 5" (from memory, can't check
from here), meaning "send a keepalive request every second, fail after
5 seconds without reply".

I use this on a BGP setup between to partner companies, no connection
to the Internet, "stability and robustness in the face of 100K routes"
is a non-issue here, but "fast fail-over" *is*. So use with care.

Also, you can decrease the default 60 seconds update interval between
neighbours to something like 5 seconds or so. I forgot what the command
was, but it works nicely. USE WITH CARE, don't do this on a router
with weak CPU and many routes!

[..]
> router connected as described above. Now, suppose my router A fails.

For router failurers, lowering the timers will work fine (see above).

It's prone to lead to flapping if some infrastructure in between is
unavaible for a few seconds, so the default is very defensive, and this
is a Good Thing (because long-term stability in the overall Internet
is such an important goal).

gert

-- 
Gert Doering
Mobile communications ... right now writing from *ICE to Frankfurt*
... mobile phone: +49 177 2160221 ... or mail me:  gert@greenie.muc.de



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