[f-nsp] BGP Session "crash" while other bgp sessions are established or shutted down?

[Sven Michels]

Hi there,

i've a small issue here and would like to ask if somebody has or knows the problem
or if i should ivestigate a bit more by myself ;-)

I've two foundrys bigiron connected via gigE. No "special" setup at all, no rip,
no ospf, no vrrp or stuff like that. They run Version 07.8.02dT53 and i don't
see any "normal" problems, so the hardware should be fine.

>From time to time it happens, that a bgp session drops, because a customer did
a shutdown or a link went down etc. A few times it happened that other sessions
are dropping while one session goes up or down. For example:
router1:
3 BGP Sessions:
  1. Internal (router1 to router2)
  2. Uplink ISP1
  3. Customer 1

router2:
4 BGP Sessions:
  1. Internal (router2 to router1)
  2. Uplinks ISP2
  3. Peering ISP3
  4. Customer 2

Now, Session 4 on router2 goes down (Customer did a shut). A bit later, holdtime +
a few seconds, the session to ISP1 drops (hold timer expired, sometimes from lokal
sometimes the remote neighbor reports hold time expired).

As you can see, this is not "local" to the router, it also happens across the
routers. I'm nearly able to force this when i shutdown two bigger sessions at the
same time on two different routers.

The "real" world routers of course have a few more bgp neighbors, about 30
sessions across two routers, ~8 fulltable sessions, rest below 500 prefixes.
And sometimes its like some "ping pong" game, lost one session, lose another on
the other router, then you lose one more back on router1 etc. which, well, sucks.

CPU Load raises up to 80% in such cases, and we use route maps to filter in and
outgoing prefixes. Normally the load is below 20% on all routers, mostly below
10%.

So, if someone knows about that, or maybe can point me to a problem, please feel
free to do so :)

Thanks and regards,
Sven
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