vlan with modified MAC fails to communicate

[Barney Cordoba]

--- On Fri, 3/29/13, Pablo Ribalta Lorenzo <rlp at semihalf.com> wrote:

> From: Pablo Ribalta Lorenzo <rlp at semihalf.com>
> Subject: vlan with modified MAC fails to communicate
> To: freebsd-net at freebsd.org
> Date: Friday, March 29, 2013, 7:53 AM
> Hi there!
> 
> Lately I've been investigating an issue that I would like to
> share, as I feel I may have to attack it from a different
> end.
> 
> I have an ethernet interface from where I create a vlan.
> Once I set up the ip address in the vlan I can ping
> correctly on both
> sides. The issue arrives when I try to change the MAC
> address of the vlan, as from then on it fails to communicate
> unless:
> 
> - I restore vlan's MAC address to its previous value
> - I enable promisc mode.
> 
> It's also worth to mention that my current setup is FreeBSD
> 8.3 and the NIC driver I'm using is not fully mature.
> 
> I was wondering if this behavior is due to some limitations
> in the NCI driver I'm using or if in fact it's the correct
> way to
> proceed, as it was possible to reproduce this same issue in
> FreeBSD 8.3 and FreeBSD CURRENT versions, even using more
> mature
> NIC drivers as 'em' and 're'.
> 
> Could somebody please shed some light in this? Thank you.
> 

Without looking at the code, it's likely that you should be changing
the MAC address BEFORE you set up the VLAN. The mac is probably being
mapped into some table that being used to track the vlans.

BC