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L2TP EoIP/BCP Bridge MTU/MRU Recommendation

Posted: Sat Jun 20, 2020 5:39 pm
by TimGuyUK

We are having some issues with some of our L2TP / bridged connections, Ill maybe post more in another post of the l2tp disconnections that weve been getting but would you clever people recommend the MTU/MRU for not only the L2TP but also the bridge?

We started originally with L2TP IPSEC running EoIP bridge/vlan we set the EoIP and Bridge to 1500 but we didn't know what to set the L2tp MTU / MRU to take that 1500 into account. We have since moved onto the BCP after getting L2TP disconnects. Basically if we copy sustained data over the bridge it will disconnect after a short period of time. The BCP is still dropping the L2TP connections. We still don't know what the set the L2TP to. I have found one post that suggested 1504 MTU and 1600 MRU but then would that effect the 1500 of the bridge.

Can you guys suggest the MTU/MRU for L2TP, Bridge (and EoIP if we decide to put it back). If it makes a different, Local connection is ethernet 1Gb, endpoints are all ethernet from 200Mb upwards but do vary. We do have 4+ other connections configured the same and they do not drop so we are unsure if it really is the MTU/MRU but we need to get that stable first.

EDIT - I notice that the L2TP MTU has set itself at 1596 with the bridge set at 1504