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MPLS MTU problem with AT&T OPT-EMAN

Aaron D
Level 1
Level 1

We are performing a data center migration. The customer had purchased an AT&T L2 interconnect via OPT-EMAN. The weren't told of the limitations of 50 MAC addresses on those links. Therefore, the L2 trunk for the DC vlans would not function due to the MAC limitation. At this point, we turned to MPLS Psuedo wire as a solution around the MAC limitation. This worked to an extent. Now we are running into another problem. MTU. The OPT-EMAN service is limiited to packet sizes of 1514/1518 (trying to confirm which now). With the MPLS 4 byte tag we are adding we are over the MTU of the link. This is causing issues with applications that are sending larger packet sizes.

Does anyone have some ideas on how to either fragment the packets, tunnel this traffic or solve this issue?

We've tried the MTU, MPLS MTU commands but so far haven't had success. Any guidance on this is appreciated.

1 Reply 1

Level 1
Level 1

On our AT&T OPT-E-MAN circuit we had a slow login issue with Windows XP PC's and the fix was to bump up the router MTU to 1504. I did not have any issues with jumbo packets so not sure if this will help.

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