[c-nsp] MPLS design in a non-MPLS cored network - was Re: MPLS and VLAN on same FE or GE interface ?

[Reuben Farrelly]

Tim Franklin wrote:
> On Wed, July 4, 2007 10:24 am, Code Monkey wrote:
> 
>> Back in 2003 I failed miserably at configuring two 7206 VXR so that
>> their FE interfaces could be connected to a VLAN switch, running MPLS
>> in one VLAN and non-MPLS in other VLANs.
> 
> I've done this in a previous life, using the on-board ports on the I/O
> controller, one VLAN for tag-switching and one for vanilla IP.  (For
> different reasons, relating to IPSec hairpinning mis-features, but the
> same set-up).

I am in the process of reworking/migrating some of our existing infrastructure 
- and working with tagged MPLS and VLAN traffic in this sort of config is 
certainly something I expect I will doing real soon.

In our situation we have 4 7200s/NPE-G1s running MPLS at diverse sites but 
also have 3550s and 3750s routing in the core of the network, and another 4 or 
5 7200s about to be merged as part of a network migration with another ISP 
quite soon.

Obviously without core switches which understand and support tagging, it seems 
like we are somewhat limited in terms of choices for expanding our MPLS mesh 
without creating an even mess of hacks (presently set up with P-2-P GRE 
tunnels, an ATM PVC and trunks which can carry tagged VLANS).  We are running 
OSPF internally throughout the network, and it carries all our customer routes 
in it (about 350 summarised prefixes).

What does and doesn't work generally speaking?  Does it require, as I suspect, 
a fairly detailed and careful design to make sure no MPLS tagged traffic hits 
the core switches at L3 at all?

How do you do this if like us you're running iBGP for MPLS and need loopbacks 
to talk to each other?  Instances of isolated VRF-lite config on the MPLS 
devices linked at L2 possibly in a ring design, to contain and control a 
separate routed redundant backbone that -is- fully MPLS aware?  Or just 
flatten the 3550/3750s to be only L2 devices?

I am interested to know what resources/designs/tips/feedback people can offer 
in this sort of situation, which I gather is much like that of the OP.  There 
doesn't seem to be huge amounts of information around for those of us who 
don't have the resources to do a full infrastructure rebuild with the latest 
cabinet sized chassis :-)

Thanks,
Reuben