From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 16 Jan 2008 10:31:17 -0800 From: Stephen Hemminger Subject: Re: [Bridge] MAC addresses on ports Message-ID: <20080116103117.4392ae65@speedy> In-Reply-To: <478E102C.8050006@satca.net> References: <478E102C.8050006@satca.net> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit List-Id: Linux Ethernet Bridging List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Marian Jancar Cc: bridge@lists.linux-foundation.org On Wed, 16 Jan 2008 15:09:48 +0100 Marian Jancar 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.