[c-nsp] q-in-q on 6500 port MTU ?

[Jeff Fitzwater]

This is first time I have to implement Q-in-Q to transport some groups internal VLANS through our core 6500s at L2.

I know how to enable the tunnels but I am not confident on the L2 MTU size.   Since the packets will be increased by 4 bytes then I would assume I need the MTU increased by 4 on all switch ports that transport the tunnel in order to pass a frame that is 1500 without dropping it.  Since I am not routing these packets then the IP MTU doesn't come into play for fragmentation.

If I change the port MTU to 1504 will it change the IP MTU globally and if so does that mean I have to reset the switch for it all to take effect?



Thanks for any help.

Even more confused than yesterday!



Jeff Fitzwater
OIT Network Systems
Princeton University