23456 without AS4_PATH?

Emanuel Petr emanuel.petr at nic.cz
Mon Mar 2 05:44:42 CST 2009


Saku Ytti wrote:
> On (2009-02-28 18:05 +0100), sthaug at nethelp.no wrote:
> 
>>> show route 195.128.231.0/24 detail
>>> [..omitted..]
>>>                 AS path: AS2 PA[5]: 39792 35320 AS_TRANS AS_TRANS 35748
>>>                 AS path: AS4 PA[4]: 35320 3.21 AS_TRANS 35748
>>>                 AS path: Merged[5]: 39792 35320 3.21 AS_TRANS 35748 I
>>> [...omitted...]
>> Agreed, that sounds wrong. However, that's not how the route appears
>> from here:
>>
>>  show route 195.128.231.0/24 detail | match "AS path: [0-9AM]"
>>                 AS path: AS2 PA[5]: 3356 13249 6886 AS_TRANS 35748
>>                 AS path: AS4 PA[4]: 13249 6886 196629 35748
>>                 AS path: Merged[5]: 3356 13249 6886 196629 35748 I
>>                 AS path: AS2 PA[6]: 1299 3356 13249 6886 AS_TRANS 35748
>>                 AS path: AS4 PA[4]: 13249 6886 196629 35748
>>                 AS path: Merged[6]: 1299 3356 13249 6886 196629 35748 I
>>
>> So in our case the AS4 path seems normal.
> 
> Looks OK in cisco as-dot format too, so unlike first example, I think
> this may be local problem.
> 
> gw.ip.fi#show ip bgp 195.128.231.0/24 
> BGP routing table entry for 195.128.231.0/24, version 29
> Paths: (1 available, best #1, table Default-IP-Routing-Table)
> Multipath: eBGP
>   Not advertised to any peer
>   3292 3356 13249 6886 3.21 35748, (received & used)
>     62.237.167.25 from 62.237.167.25 (62.236.0.5)
>       Origin IGP, localpref 100, valid, external, best
>       Community: 3292:1101 3292:1901
> gw.ip.fi#
> 

 >
We have same result, like the first example from Steinar Haug.

 > show route 195.128.231.0/24 detail | match "AS path"
                 AS path: AS2 PA[6]: 15685 29208 35320 AS_TRANS AS_TRANS 
35748
                 AS path: AS4 PA[4]: 35320 196629 AS_TRANS 35748
                 AS path: Merged[6]: 15685 29208 35320 196629 AS_TRANS 
35748 I
...
                 AS path: AS2 PA[7]: 9002 13249 13249 13249 6886 
AS_TRANS 35748
                 AS path: AS4 PA[6]: 13249 13249 13249 6886 196629 35748
                 AS path: Merged[7]: 9002 13249 13249 13249 6886 196629 
35748 I


Note: If propagated via AS196629,AS35320,.... then the AS4_PATH contains 
AS_TRANS.

Em.




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