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I am installing a metro ethernet link from my office to my data center. The office will have a cisco 3750 with several vlans. The data center end will have a more complicated set up. The metro e from the office will connect to a 2960, which will have two other 2960s with a few vlans and a 2811 router connected to it for connectivity to our other environments and the internet.

I am looking at implementing this by connecting the office 3750 and the data center 2960 with a dot1q trunk and doing all routing at the 2811. I will configure subinterfaces for gateways for each of the vlans on the 2811. I work for a small company and don't have much of a budget for an ideal architecture. I can post a simple diagram if needed for clarification.

Is there anything I am missing here? I feel like I am forgetting something very basic and want to make sure I eliminate any boneheaded mistakes.

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1 Answer 1

It sounds like your proposed solution might run into a couple of limitations, depending on how your metro-E provider does things.

Firstly, by running VLANs over the metro-E circuit, you may be running QinQ then (your tags inside a metro-level provider tag). Their gear (hopefully) is set up to handle this, but if it's not, you'd notice it by seeing a reduced usable MTU on the link.

Secondly, the metro-E providers I'm familiar with have limits on the number of MAC addresses they want to learn from you buried in the fine print. It's often a better idea to use the metro-E circuit as a layer-3 handoff between routers, then to carry a whole LAN between 2 points, unless it's absolutely necessary to do so.

If the metro-E circuit is actually MPLS/VPLS under the hood, then neither of these caveats may apply.

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Thanks for your answer. The metro-e circuit will be configured as transparent, where no QinQ tunneling is needed. It seems like the QinQ option is their default, because after speaking with their sales engineer, we decided the transparent option was the best way. There are no limitations on mac addresses that I am aware of, but I will confirm again. Unfortunately, I do not have the option of doing a Layer 3 handoff (costs too much). I would much rather do it that way. –  Eric Dec 9 '10 at 19:21

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