[c-nsp] asr 920 - lower mpls mtu?

Lukas Tribus luky-37 at hotmail.com
Sun Jun 19 09:51:03 EDT 2016

> The strategy I was going for until now was just max mtu, which happened
> to be 9216. This is the same as discussed in cisco support forums in 
> this thread:
> https://supportforums.cisco.com/discussion/11646501/eompls-mtu-size

But this is about the MTU size on the MPLS link, where those points a made may not apply (because they are more about the VC's MTU).

>  So, the question now is, what IS a likely baseline then? In my network 
> I honestly don't think I will see much more than 1500 payload + vlan + 
> mpls, but the day may come when something else comes along like a 
> customer with a 9000 byte mtu requirement for their iscsi? Maybe 9100 is 
> a good number?

I think that's a good number, yes.

>> Slightly related: the maximum MTU on an ASR920 interface seems to be 9216,
>> however it appears that packets get drop if higher than 9214 (ip ping to the
>> next-hop IP, non-labeled). Anyone seen this already?
> I have just tried this (ASR920 <-> ME3600) and don't seem to have that
> problem, just FYI.

Thanks, I did had a ME3600 on the other side as well. The asr920 was a 12sz-im
though, which is slightly different than the other 920's (different ios image, first
of all).



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