[c-nsp] BGP neighbor not establishing session

[Phil Mayers]

>> I'd suspect MTU issues here.
>>
>> Cheers,
>>
>> Mark.
>
> It's looking like it somehow might be related to that.  For a test, we
> set the mtu on the toro-router2's interfaces back to 1500 from 9216.
> After that was done, the sessions to the vanc routers both came up!
> Strange because we didn't change any of the mtus on the vanc
> routers.....they're all still 9216.

I can't comment on the platform; but I do know that BGP path-mtu 
discovery is a new-ish feature in IOS e.g. it was added on 6500/7600 in 
12.2(33)S images.

You mentioned you upgraded - maybe that's it?

There is a "neighbor" statement to disable the path mtu:

no neighbour X transport path-mtu-discovery

...of course, fixing the path MTU is better!