From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: Bridge stays down until a port is added Date: Sat, 20 Aug 2011 09:30:59 -0700 Message-ID: <20110820093059.75c37a1f@nehalam.ftrdhcpuser.net> References: <20110811070659.GA21307@torres.zugschlus.de> <20110811081706.7307e8b2@nehalam.ftrdhcpuser.net> <20110811205429.GB21307@torres.zugschlus.de> <20110820094712.GC21307@torres.zugschlus.de> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, Sven-Haegar Koch To: Marc Haber Return-path: Received: from mail.vyatta.com ([76.74.103.46]:60196 "EHLO mail.vyatta.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753198Ab1HTQay (ORCPT ); Sat, 20 Aug 2011 12:30:54 -0400 In-Reply-To: <20110820094712.GC21307@torres.zugschlus.de> Sender: netdev-owner@vger.kernel.org List-ID: On Sat, 20 Aug 2011 11:47:12 +0200 Marc Haber wrote: > Hi, > > I was a little bit confused. The problem is that with IPv6 an IP > address configured on a bridge which is still in the NO-CARRIER state > will never leave tentative state and will thus not get useable. > > On Fri, Aug 12, 2011 at 02:22:27PM +0200, Sven-Haegar Koch wrote: > > For me (using kernel 3.0.0) it seems to work as I expect it: > > > > aurora:~# brctl addbr br0 > > aurora:~# ifconfig br0 192.168.254.1 netmask 255.255.255.0 up > > aurora:~# ping 192.168.254.1 > > PING 192.168.254.1 (192.168.254.1) 56(84) bytes of data. > > 64 bytes from 192.168.254.1: icmp_req=1 ttl=64 time=0.087 ms > > Now try it with IPv6. > The problem is that IPv6 Duplicate Address Detection needs to work. This is not a simple problem. If the bridge asserted carrier with no ports then: 1. IPv6 address assigned and IPv6 decides it is okay. 2. Port added later 3. Another system has the same address. *broke* If you want to avoid DAD, then you can configure disable DAD by setting /proc/sys/net/ipv6/conf/br0/accept_dad to 0