[c-nsp] ASR1k to ASR9k CLNS MTU problems

[Mikael Abrahamsson]

On Tue, 28 May 2013, Pshem Kowalczyk wrote:

> ASR 9k calculates the MTU differently to ASR 1k. We've settled on the 9k 
> way of calculating MTU and adjust all other platforms with "clns mtu". 
> Our network runs mostly on ~9100, so XR uses 9114 as interface MTU and 
> 9097 as CLNS MTU (calculated by XR). On other platforms (xe and classic 
> ios) we apply interface MTU of 9100 with "clns mtu 9083". I'm guessing 
> that XR takes the source/destination MAC and ethertypes field into 
> consideration for CLNS frames (14 bytes), but other platforms don't. I'm 
> not sure where the initial 9097 comes from though.

If you configure main interface mtu 9114 on ASR9k and 9100 on IOS, 
it should just work out of the box, no need to adjust clns mtu or any 
other protocol MTU.

Both Juniper and IOSXR includes the 14 byte ethernet header in the MTU 
calculation. IOS does not.

-- 
Mikael Abrahamsson    email: swmike at swm.pp.se