[c-nsp] MPLS over VLAN

[Phil Mayers]

On 04/26/2010 10:32 PM, Paul Stewart wrote:
> Can someone explain this a bit better for me? ;)   Sorry if this is "MPLS
> 101"...
>
> We are getting ready to deploy some equipment (mixture of Cisco/Juniper)
> that is MPLS capable.  We'd like to transport some VPLS traffic however in
> the middle of a few of the links are layer2 switches - we've been told this
> isn't possible even with 1600 MTU frame size supported.... Juniper is

That sounds unlikely; 1600 bytes should be sufficient for VPLS I think.

> telling us (in one particular segment) that we must hang MX gear in there to
> make it work with MPLS...
>
> Just looking to clarify MPLS type traffic over VLAN layer2 equipment and
> works and doesn't work and why.... as you can tell we're fairly new to the
> MPLS side of things but hoping to get up to speed soon...

MPLS is basically ethernet packets with a destination mac, ethertype, 
some MPLS labels, then the original packet. The MPLS packets will flow 
over any ethernet switch provided said switch will support the MTU.

*Terminating* the MPLS LSP is a whole different ballgame, and in 
particular you want to be very sure your Cisco gear supports VPLS. The 
6500 does not with LAN cards, for example.