From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pascal Hambourg Subject: Re: Forced lladdr change with bridge - or not? Date: Mon, 23 Aug 2010 10:13:48 +0200 Message-ID: <4C722DBC.6060000@plouf.fr.eu.org> References: <835126759.1436781282547490956.JavaMail.root@tendai.telenet-ops.be> <632287680.1437041282547640257.JavaMail.root@tendai.telenet-ops.be> Mime-Version: 1.0 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <632287680.1437041282547640257.JavaMail.root@tendai.telenet-ops.be> Sender: netfilter-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="iso-8859-1" To: Bart De Schuymer Cc: netfilter@vger.kernel.org, Jan Engelhardt bdschuym@telenet.be a =E9crit : > You're right. The Linux bridge does just what the 802.1D standard > recommends > (http://standards.ieee.org/getieee802/download/802.1D-2004.pdf): > "7.12.5 Unique identification of a bridge > A unique 48-bit Universally Administered MAC Address, termed the Brid= ge > Address, shall be assigned to each Bridge. The Bridge Address may be > the individual MAC Address of a Bridge Port, in which case, use of th= e > address of the lowest numbered Bridge Port (Port 1) is recommended." Thanks for the explanation. > Apparently you can get around this problem, see (I didn't verify): > http://backreference.org/2010/07/28/linux-bridge-mac-addresses-and-dy= namic-ports/ "if the bridge's MAC address is forced to a specific value, the bridge "remembers" that and makes the address permanent. But there's a caveat: the address must belong to one of the devices enslaved to the bridge" Hmm, I remember I had a similar idea, but it didn't work : the address was not permanent and could still be replaced if an interface with a lower MAC address was added. Maybe I didn't do things right, I will try again, thanks. I had the idea that maybe it was a kernel change, so looking at the kernel changelogs, I found this in ChangeLog-2.6.27 : > commit 92c0574f11598c8036f81e27d2e8bdd6eed7d76d > Author: Stephen Hemminger > Date: Tue Jun 17 16:10:06 2008 -0700 >=20 > bridge: make bridge address settings sticky >=20 > Normally, the bridge just chooses the smallest mac address as the > bridge id and mac address of bridge device. But if the administra= tor > has explictly set the interface address then don't change it. At the time I tried to force a permanent MAC address to the bridge I used a kernel older than 2.6.27, this explains why it didn't work.