Any Transport Over MPLS (AToM)

Davis,
With a network backbone that doesn’t support jumbo frames (meaning frames larger than 1500), you might have some trouble. Common practice is to set the entire core to support an MTU of 9216. You would have to support 14 bytes for Ethernet, 4 bytes for a VLAN tag (if you are using 802.1Q), 4 bytes for MPLS. So, far, that is 22 bytes of overhead, which would reduce your payload size to 1478. Whether you can force your MTU down so your core won’t exceed 1500 bytes, I just don’t know.

I did find an article that might be of help, though:
http://www.netcraftsmen.com/working-with-eompls/

In the article, it states that the MTU on the physical ports must be set to at least 1504, and that the x-connect protocol actually checks to see whether the other end of the circuit has the same MTU.

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