[c-nsp] ASR 1k, 3.1.0S MTU issues on PortChannel interfaces

[Mark Tinka]

On Friday, November 19, 2010 05:20:49 am Pshem Kowalczyk 
wrote:

> Yet another update. I turns out that the old 'turn it off
> and on again' worked. After I reload the box I got the
> MTU of the subinterfaces at 4400, which is good. I still
> had to use clns mtu (of 4379) to make it work.

Which box did you "reload"? The ASR1000, or both?

I've found, in the past, that it has been necessary to bump 
the interface on which an MTU change has been applied, for 
that change to take effect, regardless of what "show 
interface" displays.

I'm not sure if this applies to all versions of IOS, or just 
a few, but on the 7200's that we've worked with, it's been 
needed the few times we've had to do it.

I can't say whether it's common to do so these days, as we 
normally pre-stage boxes before they are connected to the 
network, so a change in link state effects whatever MTU has 
been configured at the time of connection.

As for IOS XR, we haven't had to bump interfaces to get 
MTU's to change.

Obviously, the worst case is when you have to reboot the 
Catalyst switches when the system MTU for interfaces is 
changed. Luckily for you, your switch in between both boxes 
was good to go.

Cheers,

Mark.
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