23456 without AS4_PATH?

Sat Feb 28 17:05:34 UTC 2009

> Take a watch on this route:
> 
> 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...]
> 
> AS4_PATH contain AS_TRANS, it's also RFC violation, isn't it ?

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: 9002 13249 13249 13249 6886 196629 35748 I
                AS path: 9002 13249 13249 13249 6886 196629 35748 I
                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.

Steinar Haug, Nethelp consulting, sthaug at nethelp.no