Re: Strange BGP announcement.

[George Matey <gmatey () BayNetworks COM>]

At 07:30 AM 11/9/98 -0600, Brett Frankenberger wrote:
> :: Scott Gifford writes ::
> > > > > Bays don't crash (at least not in the general case ... for example,
> > > > > mine stayed up this time and the last time this happened), but
they do
> > > > > send a NOTIFY and bring down the BGP session, as required by the
RFC. 
> > > > > (I believe gated does this also.)
> >
> >   In case any Bay Networks users didn't already know this, reasonably new 
> > version of the system software have a switch to turn off this behavior:
> >
> > 1:TN]$g wfBgpPeerEntry.41.*
> > wfBgpPeerEntry.wfBgpPeerASLoopDetect.157.130.101.182.157.130.101.181 = 2
> > wfBgpPeerEntry.wfBgpPeerASLoopDetect.204.70.16.38.204.70.16.37 = 1
> > wfBgpPeerEntry.wfBgpPeerASLoopDetect.204.70.100.66.204.70.100.65 = 1
> > wfBgpPeerEntry.wfBgpPeerASLoopDetect.209.54.51.230.209.54.51.229 = 2
> > wfBgpPeerEntry.wfBgpPeerASLoopDetect.209.54.101.238.209.54.101.237 = 2
> >
> > [1:TN]$set
wfBgpPeerEntry.wfBgpPeerASLoopDetect.204.70.100.66.204.70.100.65 2
> >                           (41)                  (interface)
> > [1:TN]$commit
> >
> >   Set this flag to '2' for each interface to keep your router from tearing
> > down BGP sessions when it finds a loop.  Don't forget to commit 
> > afterwards, and then to do a "save config config" so it will take after 
> > you reboot.  
>
> This wasn't a loop.  This was a malformed AS path.  The length of the
> entire AS Path attribute was 14 bytes, and the length of the first AS
> Sequence segment was 7 AS's, even though there wasn't room to fit that
> many in 14 bytes.  (7AS's * 2 bytes each + 2 bytes for the segment
> header, gives a minimum of 16 bytes needed.)
>
> Does this attribute also disable detection of malformed AS Paths? 

No.

--
George

 
>          - Brett  (brettf () netcom com)
>
> ---------------------------------------------------------------------------
---
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Frankenberger
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