Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262097AbVD0XbZ (ORCPT ); Wed, 27 Apr 2005 19:31:25 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262098AbVD0XbZ (ORCPT ); Wed, 27 Apr 2005 19:31:25 -0400 Received: from e33.co.us.ibm.com ([32.97.110.131]:56284 "EHLO e33.co.us.ibm.com") by vger.kernel.org with ESMTP id S262097AbVD0XbX (ORCPT ); Wed, 27 Apr 2005 19:31:23 -0400 In-Reply-To: To: Kyle Moffett Cc: Felix von Leitner , linux-kernel@vger.kernel.org, netdev@oss.sgi.com, Pekka Savola , "YOSHIFUJI Hideaki / ?$B5HF#1QL@" MIME-Version: 1.0 Subject: Re: IPv6 has trouble assigning an interface X-Mailer: Lotus Notes Release 6.0.2CF1 June 9, 2003 Message-ID: From: David Stevens Date: Wed, 27 Apr 2005 16:31:18 -0700 X-MIMETrack: Serialize by Router on D03NM121/03/M/IBM(Release 6.53HF294 | January 28, 2005) at 04/27/2005 17:31:19, Serialize complete at 04/27/2005 17:31:19 Content-Type: text/plain; charset="US-ASCII" Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1611 Lines: 31 netdev-bounce@oss.sgi.com wrote on 04/27/2005 03:57:05 PM: > On Apr 26, 2005, at 02:10, Felix von Leitner wrote: > > OK for unicast. But multicast? I expected link-local multicast > > to send on _all_ interfaces if I don't specify one. (I didn't see the article this is quoting-- apparently wasn't CC-ed to "netdev" as the original was). Multicasting doesn't work that way. Multicast group memberships are per-device (whether or not they are link-local). If you join the same group address on two different devices, they'll only be the same group if there are multicast routers on the two links connecting them in the same multicast routing hierarchy. With a scope broader than link-local, and a multicast router on that link, the packets can be forwarded to other links, but they won't be forwarded to every host on the internet in that group (!), and there are sometimes good reasons for having different partitions of the same group within a single organization. So, the same group number on two different links is not necessarily the same group. It depends entirely on whether the two groups have common multicast routers with no policy restricting forwarding for that group between them. This is how IPv4 multicasting works, too. You join a group on a particular device. +-DLS - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/