New to MPLS

Unanswered Question
Jun 21st, 2007

I have a client who wants to do some MPLS. While I feel I have a good understand of the concept of MPLS, I currently lack the knowledge and experience to know how to properly design it.

The client has 2 7200s and 2 3560s in POP1 and another 7200 and 3560 in POP2. In POP1, each 7200 has a physical connection to each of the two 3560s, and the 3560s have a physical connection to each other - it's all fully meshed (with the exception that each 7200 does not have a physical connection to the other 7200). POP2 is easy - the 7200 is connected to the 3560.

My client has done a conceptual diagram labeling the 7200s as P routers and the 3560s as PE routers in each POP. A client connection is illustrated in the diagram connecting to one of the 3560s in POP1 and the 3560 in POPs. That describes the client entry points into the MPLS cloud.

I was doing some reading, and correct me if I'm wrong, but it seems the 3560 has a very limited MPLS feature set - in fact it doesn't really have an MPLS feature set at all. It does seem to have enough to run as a CE, but not a PE as the client has illustrated in their diagram. Assuming this is true and the 3560s cannot run as PEs, I have to run them as CEs. The question now, is the 7200s that were labeled as P routers now need to be PE routers because CEs cannot talk directly to Ps, or am I wrong?

Just by browsing this forum briefly, it appears that P routers are somewhat optional and one may opt to start to build using PEs and install Ps as the network grows. Also from reading some of the software configuration guides on MPLS, it appears that a client can only talk to a CE, not a PE. Assuming these two points are true, I really do need to look at redesigning what my client has given me - turn the 7200s into PEs instead of Ps and turn the 3560s into CEs instead of PEs. Is that even possible? If the 7200s reach one another through the 3560s only, can a CE transit for a PE ok, or am I going to wind up in some hot water?

Thanks, and I apologize in advance if any of these questions have simple, obvious answers that I am missing.

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swaroop.potdar Thu, 06/21/2007 - 06:56

Yes its possible to do MPLS with the existing constraints and devices you have got.

P routers would be needed in larger deployments and useful for when just large number of packet switching is to be done.

SO with the existing small setup, you can run it without P's.

Pop 1 : You run a trunk between 2 switches, drop a vlan x for port 0/0 of both 7200, and vlan y for port 0/1 of both 7200. Connect the end clients to the switch in their respective vlans. Dont create any SVI;s for the vlans connecting the 7200's.

Connect the third port of the NPE to one switch each. Assign it to a vlan on the switch and drop a vrf on the the NPE side.

This third port on the NPE would be your PE-CE link.

You will create SVI for the PE-CE vlan and other client vlans and thus have intervlan routing enabled for these service vlans only.

Configure your 3 7200 with label switching and LDP with MPBGP and you are set to go.

PS: Be careful of backdoor link you just created between the PE at PoP1 based on the IGP you will be using and use a appropriate mitigation mechnism.

Pop 2 : fairly simple as you said, just connect clients in their respective vlans on the switch.



jschwam Sat, 06/23/2007 - 21:48

Does the client want to build their own MPLS core or just connect a few location using MPLS technology from a service provider?

If it is from a provider then all you need to be concerned about is the CE. In the case of the CE there are no MPLS configurations just your layer-2 connection (T-3 or T-1) and then the layer-3 (IP) address.

There are layer-2 VPLS providers who give Ethernet hand-off and in this case you can connect to any device with an Ethernet port on it (3560 or router w/ an Ethernet interface).

I hope this helps.


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