nanog mailing list archives

Re: 23456 without AS4_PATH?


From: Emanuel Petr <emanuel.petr () nic cz>
Date: Mon, 02 Mar 2009 12:44:42 +0100

Saku Ytti wrote:
On (2009-02-28 18:05 +0100), sthaug () 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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