L2tpv3 mtu considerations

jeffersoncbriones · ‎06-09-2010

Dear Gurus,

Im curently using other router brands to use l2tpv3 and i can see issue on the frame size. it can only transfer 8Mbps on 1500 frame size and 40Mbps on 1300bytes frame size. Does cisco brand also like these ? Is this technology limitations or just the brand?

tia.

Giuseppe Larosa · ‎06-10-2010

Hello Jepoy,

I can only say that I was able to build an ISIS adjacency over an L2TPv3 pseudowire without any need to adjust clns mtu as I had expected

ISIS uses hellos = supposed MTU so it is similar to using IP packets of size 1500 byte.

Clearly the device needs to fragment the L2TPv3 PDU in order to cross links in the middle towards remote PE node.

It is wise in this cases like when using PPPoE or forms of IPSec and/or GRE to reduce MTU to avoid fragmentation otherwise buffers are stressed to handle the fragments at the other L2TPv3 endpoint.

Hope to help

Giuseppe