[c-nsp] more mpls, mtu, etc., questions

[Kristofer Sigurdsson]

AFAIK, mtu is a per-physical interface setting.

However, you can set the mtu of the physical interface to, say, 4470,
and the ip mtu of each interface to the desired value for that 
subinterface...that may help your situation.

On Tue, 2005-11-22 at 16:38 -0500, Alex Rubenstein wrote:
> 
> So, I've run into another issue related to the earlier dicusscion of MTU, 
> and MPLS.
> 
> We have a 7206, with a C7200-I/O-GE+E. The interface is running dot1q, and 
> has two vlan subint's facing the core, and some vlan subints facing 
> customers.
> 
> For the core facing subints, I'd like to run jumbo, 4470 or larger. I do 
> this by typing "mtu 4470" on interface gi0/0.
> 
> However, when I try to make a customer facing vlan subint, it won't come 
> up because of a MTU mismatch (the far end router has a MTU of 1500). I try 
> to change the mtu on the subint facing the customer, and
> 
> xxxx.zzz(config-subif)#mtu 1500
> % Sub-interface GigabitEthernet0/0.324 does not support user settable mtu
> 
> So, to solve this problem for the immediate term, I have set the mtu of 
> gi0/0 to 1500, but tag-switching mtu to 4470. This allows for it to come 
> up, and work.
> 
> However, this doesn't allow for l2tpv3 connections to work, because of the 
> mtu of 1500 on the physical interface.
> 
> Juniper allows this by having per-subinterface settings of each type 
> of MTU.
> 
> Any thoughts on this?
> 
> 
>