[j-nsp] Odd BGP Issue

Lee Hetherington lee.hetherington at redtechnology.com
Sat Jul 5 15:10:36 EDT 2008

Thanks Scott...

I am peering with interface addresses...

I have specific export statements which export a particular filter list, which only includes a /23 of addresses.  For some reason when showing what I am advertising to AS1200 i'm announcing the full route table.  I am surprised an ISP would accept such routes from me, I expect their network is going a bit mental every time I fire up the session again.


-----Original Message-----
From: Scott Morris [mailto:swm at emanon.com]
Sent: Sat 05/07/2008 20:02
To: Lee Hetherington; juniper-nsp at puck.nether.net
Subject: RE: [j-nsp] Odd BGP Issue
I've seen this type of thing before with the random dropping and "hold time
exceeded" message when a routing loop has been introduced.

Are you peering to a loopback on your peer's router, or to the directly
connected physical link?  Watch to be sure you aren't learning through BGP
the connected links or loopback interfaces you are connecting to as this may
be causing some issues.

Do you have traceoptions on your bgp sessions at all?  Perhaps that could
give you better details as the routes all come in and your router tries to
sort things all out, something is irritating it, so perhaps it will tell you

BGP sorts a number of things out with its series of bestpath selection
algorithms, but if you have done anything else to modify these or just
exactly how/where bgp fits into the rest of your routing scenario it may
cause issues.



-----Original Message-----
From: juniper-nsp-bounces at puck.nether.net
[mailto:juniper-nsp-bounces at puck.nether.net] On Behalf Of Lee Hetherington
Sent: Saturday, July 05, 2008 2:45 PM
To: juniper-nsp at puck.nether.net
Subject: [j-nsp] Odd BGP Issue

Hi All,

I have a very odd problem with a J Series router and wonder if anyone can
help, as neither our providers nor JTAC can shed any light on this one.

We have a J2320-JH, it has a Link to AS1200 over a 2meg serial x.21
connection and then a 100meg connection to AS1299 over ethernet.  I have bgp
from our as accepting ANY from them and announcing a single /23 network to

My original 2meg connection has been stable and running a BGP session with
no flapping for almost 3 weeks now.  As soon as I introduce the new peer,
the route table increases as you'd expect to around 500k routes, becomes
stable with 245k active routes and then the originally stable connection
starts to flap giving a Hold Timer Expired Error.  This then keeps flapping.

Whilst this first session is flapping there are no errors on the interfaces
to either AS1200 or AS1299.  However, whilst the session is flapping I note
that almost exactly 1mbits/sec is going out of our new AS1299 connection and
comming into our AS1200 connection.  This traffic however does not come onto
our LAN as the gig connection to our switch is showing none or very minimal

The guys at AS1200 havent got back to me yet, but the guys from AS1299 have
told me to check my prefix-limit, but I dont currently have this configured.
JTAC tell me my router is fine and my configuration is correct.

Anyone have an idea?  The providers seem to be stumped but this leaves me
with one peer disabled currently.



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