Subject: Re: VLAN and ARP failure on tg3 drivers

From: Benny Amorsen <[email-masked]>
Date: Mon, 26 Oct 2009 09:20:48 +0100

Gertjan Hofman <[email-masked]> writes:

> Dear Matt, Eric, Benny,
>
> Sorry about the slow response to your fast replies. I think Benny is
> correct, the 'problem' lies in the fact that we were using a VLAN ID
> of 0, without knowing its special significance. User error.
>
> I tested it with other VLAN id's (>0) and it appears to work fine. We
> are not entirely sure we understand  why it used to work with VLAN ID
> 0 on the Broadcom chips and still does with a number of different
> cards (with >2.6.27 kernels).  What is the 'correct' behaviour for
> this incorrect usage ?

VLAN 0 isn't incorrect, it's just surprising. When you send a packet
tagged with VLAN 0, it means that the packet should be interpreted as
being the same VLAN as a completely untagged packet.

So in theory, if both ends are using VLAN 0 and you aren't using eth0
for anything, traffic should flow, at least if both ends are on the same
kernel version. Feel free to debug why that isn't the case for you, of
course...

/Benny