Re: [Bridge] MAC addresses on ports

[Stephen Hemminger <shemminger@linux-foundation.org>]

On Wed, 16 Jan 2008 15:09:48 +0100
Marian Jancar <m.jancar@satca.net> wrote:

> Hi,
> 
> I need some explanation/help with a probably bit uncommon bridge setup. I have
> devices that come with their manufacturer MAC addresses, and I need to create
> a bridge that uses my MAC address instead and has to look about like this:
> 
> br0:    unique MAC address from my range
> wlan0:  same MAC as br0
>         (madwifi supports 4 MAC frames in STA mode so the actual bridging works,
>         just if you are curious :p)
> eth0:   any MAC address higher than the br0 MAC,
>         and as long as the assumptions below hold, unique in just this bridge,
> eth1:   ditto
> ...
> ethN:   ditto
> 
> 
> Now, the only reason I can think about from my naive point of view, why the bridge
> cares about port MAC address at all, is maintaining a reliable and persistent
> connection between the logical port and the actual physical device for STP
> purposes.
> 
> So if I'm right, I can assign any MAC addresses to the ethernet ports, as long
> as they are higher than the wlan0 address, to ensure that the bridge selects
> the wlan0 MAC as its own, and as long as they are locally unique.
> The MAC addresses of the ethernet ports will not appear in any non-STP
> packets and don't have to be globally unique, because they identify ports in
> just this bridge and STP handles that, just a port has always to have the
> same address and not a random one.
> 
> Is this correct? If not, is there any other way to create a bridge and
> not to have to allocate a unique MAC to each port?
> 
> Any comments and/or pointers to relevant documentation are highly appreciated.

Latest version of code allows bridge to have any mac address.
You do HAVE to make sure device in bridge has a unique mac address.