[c-nsp] Turning on MPLS.

[Justin Shore]

Alex A. Pavlenko wrote:
> Colleagues.
> 
> Consider the following network setup
>  
> [internet]  -  [c7301] - [cat3560G] - [cat3750] - [c7200] - [cat3550] - [customers]
> 
> Catalyst switches work as l2 and routers are "router on a stick".  
> I've tried to turn on MPLS between routers. The result config for c7200 follows
> 
> mpls label protocol ldp
> mpls ldp advertise-labels
> int f0/0.96
>  ip address x.x.x.1 255.255.255.252
>  mpls ip
> 
> Most works fine, but some customers began to complain that they can not access
> certain sites in the Internet. I'm not sure but the situation looks like there is MTU mismatch
> somewhere.  Is it mandatory to check and adjust MTUs when turning on MPLS? 
> No idea where to look else, please help.
> Thanks.

I was bit by this a few weeks ago.  In the end I bumped up all 
MPLS-enabled interfaces to 9216.  I would like to know what the best 
practice is for deploying MPLS though.  Is changing the system MTU 
recommended or should it be done on an interface by interface basis? 
Should the MPLS MTU also be set?

Justin