Strange BGP announcement.

Mon Nov 9 16:11:07 UTC 1998

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 at netcom.com)
> 
>---------------------------------------------------------------------------
---
>                               ... Coming soon to a      | Brett
Frankenberger
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> 
>