[issue589] VLAN issues

Chris Turner c.turner at 199technologies.org
Wed May 16 15:15:48 PDT 2007

Gergo Szakal wrote:
> Original thread: http://tinyurl.com/2gmn7m
> Applied patch: http://leaf.dragonflybsd.org/~sephe/vlan_promisc.diff
> I was doing the following: added a physical interface (xl0) that had no VLAN ifaces assigned and 2 vlan interfaces (vlan2, vlan3) assigned to another interface (xl1) to the bridge. I get 'invalid MTU for vlanX' errors for vlan interfaces when trying to add them to bridge0.
> Now what?

disclaimer: haven't done this meeself before, but

I read something 'one time' about the vlan tagging knocking a few bytes
out of the available space on the ethernet frame -

so your xl0:vlanX interface 'mtu' numbers are probably a few bytes
smaller than the default mtu on xl0/xl1/bridge0 (or whatever is already
on the bridge and/or not 'virtualized') .. have you tried matching them
up via "ifconfig ... mtu" ?

(e.g. might need to destroy the bridge, set the mtu on the bridge to
match the vlanX's , then re-add the vlan ifs..)

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