as_path question

[Arnold Nipper]

on 05.07.2011 14:21 Mikhail A. Grishin wrote:
> Matthew Walster wrote, 05.07.2011 16:07:
>> 2011/7/5 Mikhail A. Grishin<magr at ripn.net>:
>>> What purpose of  '{' and '}' at BGP.as_path output?
>>
>> It indicates an "AS Set" - some aggregation happened, the longer
>> routes of which were in the two ASNs in the brackets.
>>
>>> Why at 'show route' we see only '[i]'? (expected to see the first AS in
>>> as_path)
>>
>> IMO, it should show AS48467 as they were the aggregator.
> 
> Moreover, this prefix (94.228.160.0/20) was filtered and not accepted
> because of this BIRD structure:
> # Apply as_path filters on the last AS (originated route)
>   allas = [ 15905, 34211, 41206, 44116, 44893, 47773, 48467, 50875,
> 51031, 51186, 51443, 52163 ];
>   if ! (bgp_path.last ~ allas) then reject;
> 
> So bgp_path.last doesn't hit to 48467 in this case.
> Is this normal?
> 

this is at least the current behaviour. It would be great if
bgp_path.last would also be able to operate on an AS-SET.

From the top of my head I have no idea how you could do it straight
forward. You would have to break up the AS-SET and do the lookup for
each AS in the set.



Arnold
-- 
Arnold Nipper / nIPper consulting, Sandhausen, Germany
email: arnold at nipper.de       phone: +49 6224 9259 299
mobile: +49 152 53717690      fax:   +49 6224 9259 333

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