Having an issue with a DSL circuit. We have the Actiontec DSL modem in transparent bridge mode. The modem defaults to an MTU of 1500 when set this way.
I am able to get the circuit up on the ASA via PPPoE username/password. I have set the MTU on the ASA to 1500, 1492, 1464, and 1424. No matter what this is set to on the ASA it results in web traffic being extremely slow and/or fails to load. I recognized this as a probable MTU issue and did a WireShark packet capture that shows Header Checksum errors, may be caused by IP checksum offload? and an occasional "Malformed Packet".
Attached is a sho run of the ASA. Would really appreciate any ideas on this one. I can't seem to set the MTU on the ASA to resolve this. I opened a case with Cisco TAC a week ago, but so far they have been less than helpful/timely in their response. Hoping I might have better luck here.