[c-nsp] multiple vlans on a port

[Benny Amorsen]

Matthew Huff <mhuff at ox.com> writes:

> Also, with 802.1q framing, you might run into fragmentation on the
> non-native VLANs. You may want to adjust the MTU on the virtual
> machines if Linux doesn't do it automatically.

Linux, with reasonably modern kernels, automatically allows an extra 4
bytes for the 802.1q tag. You're ok, as long as the switch allows them
too.

This logic seems to break down when doing q-in-q, where you may have to
adjust the MTU to 1508 for the "untagged" device. This may be fixed in
the last few kernels; I haven't tried lately.


/Benny