Subject: Re: VLAN + bridging problems
To: Dobromir Montauk <>
From: Manuel Bouyer <>
List: tech-net
Date: 12/12/2002 21:17:24
On Thu, Dec 12, 2002 at 11:05:38AM -0800, Dobromir Montauk wrote:
> > As it is, there are four possible setups for a bridge:
> >
> > - vlan and vlan as members of a bridge -- this works correctly because
> >   vlan_input calls  ether_input recursively after it  has stripped the
> >   header and neither parent interface is the member of a bridge.
> > - vlan and ether (not parent of  vlan) -- this works correctly as long
> >   as  tagged packets  are never  recieved on  the ether  interface. If
> >   tagged packets are recieved, an extra header gets tacked on.
> > - vlan and ether (parent of  vlan)  -- this will not work for the same
> >   reason -- ether must recieve tagged packets.
> > - ether and ether -- this is the repeater scenario above
> >
> > Your setup is the third one, no?
> >
> > Basically    the  the   third  and   fourth  scenarios   are  mutually
> > exclusive. The configuration option you are asking for would be a flag
> > that would toggle between the two, correct?
> I had setup 3 originally.  I've tried setting up #2 instead, with two
> ethers, but the ether#2 is receiving the tagged packets, and the vlan is
> not.  I couldn't figure out how to reverse this, so forwarding didn't work
> either.  How do I get ether to ignore vlan packets & have vlan#95 get them
> instead?

Can you describe what you're trying to do exactly ?
I tried bridge over vlan yesterday and it worked as expected:

wm0 is connected to a trunk port of a cisco, receive all 802.1q frames
wm1 is connected to another machine via cross-over cable, and is plain
ethernet (no vlan here).

Here is what I did:
ifconfig wm0 up
ifconfig vlan0 create
ifconfig vlan0 vlan 574 vlanif wm0
ifconfig vlan0 xxx.yyy.zzz.ttt netmask 0xffffff00
ifconfig wm1 up
ifconfig bridge0 create
brconfig bridge0 add vlan0 add wm1 up

and it worked as expected.

Manuel Bouyer <>
     NetBSD: 23 ans d'experience feront toujours la difference