Broadcom bge and 802.1Q vlan tags

Ruslan Ermilov ru at
Tue Oct 12 06:20:37 PDT 2004

On Tue, Oct 12, 2004 at 08:32:38AM -0400, Don Bowman wrote:
> Roub?cek Zdenek:
> > 
> >  Hello current
> > 
> >  I have run into a problem with my Broadcom NIC (Dell 
> > LATITUDE D600). I am not able to detect 802.1Q tags on 
> > incoming interface with ethereal or tcpdump. All incoming 
> > packets seems like they are not coming through trunk but as 
> > native ETH frames, ie. the vlan tag is missing, probably 
> > removed before being passed to tcpdump?
>  ...
> do you have if_vlan loaded? try 'kldload if_vlan'.
> This happens automatically if you create a vlan interface, but
> you may not have one if you are just sniffing.
There appears to be a bug with drivers that support VLAN tag
striping in hardware in case no VLAN interfaces are configured.
In this case, ether_demux() will just proceed like if it was
an untagged Ethernet frame.  glebius@ promised to fix this bug.

Zdenek, unfortunately, the bge(4) driver doesn't allow the
user to disable hardware vlan tag striping (like, e.g., the
em(4) driver allows), so you cannot watch VLAN frames on this
box using tcpdump or ethereal.

Ruslan Ermilov
ru at
FreeBSD committer
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