[j-nsp] What does AS path attribute problem mean?

[Clay Haynes]

On Fri, Sep 9, 2011 at 1:07 PM, Jared Mauch <jared at puck.nether.net> wrote:

>        Well, the update is well formatted and proper, the handling in JunOS
> is buggy.  You don't want to just blackhole unkown items like this as you
> can
> create a significant problem for others similar to the bogon problems
> that exist.
>
>        This type of a fix is ONLY a short term fix to workaround your buggy
> software.
>
>        - Jared
>
> On Fri, Sep 09, 2011 at 12:58:36PM -0400, Andrew Parnell wrote:
> > We noticed this as well on a couple of our M7i running 9.x series
> > code, but not on others running 10.x.  This is being caused by a
> > particular prefix (212.118.142.0/24):
> >
> > rpd[5239]: xx.xx.253.192 (Internal AS xx) Received BAD update for
> > family inet-unicast(1), prefix 212.118.142.0/24
> >
> > The easy solution is to simply filter out the offending prefix.  There
> > are many ways this can be done, but the following did the trick for
> > us:
> >
> > policy-options {
> >     prefix-list bad-prefixes {
> >         212.118.142.0/24;
> >     }
> >     policy-statement BGP-Import {
> >         term block-bad-prefixes {
> >             from {
> >                 prefix-list bad-prefixes;
> >             }
> >             then reject;
> >         }
> > }
> >
> > Apply something like this to your BGP import and/or export policy as
> > appropriate and you should be fine.
> >
> > Andrew
> >
> > On Fri, Sep 9, 2011 at 11:41 AM, Markus <universe at truemetal.org> wrote:
> > > All of a sudden without changing anything in the config I'm getting the
> > > following on a M7i running 8.0R2.8:
> > >
> > > rpd[3019]: bgp_read_v4_update: NOTIFICATION sent to 89.146.xx.49
> (External
> > > AS xxxx): code 3 (Update Message Error) subcode 11 (AS path attribute
> > > problem)
> > >
> > > The other end (Cisco) is getting:
> > >
> > > %BGP-3-NOTIFICATION: received from neighbor 89.146.xx.50 3/11 (invalid
> or
> > > corrupt AS path) 0 bytes
> > >
> > > This is causing the BGP session to flap. It happens at arbitrary
> intervals,
> > > sometimes once a minute, sometimes just once in an hour. CFEB and RE
> CPU are
> > > at steady 100% when it happens.
> > >
> > > What can I do about this and what could be the cause? Help! :)
> > >
> > > Thanks!
> > > Markus
> > >
> > > _______________________________________________
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> > >
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> --
> Jared Mauch  | pgp key available via finger from jared at puck.nether.net
> clue++;      | http://puck.nether.net/~jared/  My statements are only
> mine.
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>


I have a case open with TAC on this. They recommended temporarily filtering
out the bad prefix (as others have mentioned in this thread), and upgrading
to JUNOS 10.2 or later which doesn't appear to have the issue. In the
meantime they're looking for the root cause of the flap and seeing if
there's a different way to fix it for older supported versions of JUNOS.


Regards,
Clay