From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [RFC NET 00/02]: Secondary unicast address support Date: Thu, 21 Jun 2007 12:13:05 -0700 (PDT) Message-ID: <20070621.121305.109899848.davem@davemloft.net> References: <20070620180017.6685.70611.sendpatchset@localhost.localdomain> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: kaber@trash.net, netdev@vger.kernel.org, shemminger@linux-foundation.org, jeff@garzik.org To: ebiederm@xmission.com Return-path: Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:50297 "EHLO sunset.davemloft.net" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1753267AbXFUTMr (ORCPT ); Thu, 21 Jun 2007 15:12:47 -0400 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org From: ebiederm@xmission.com (Eric W. Biederman) Date: Thu, 21 Jun 2007 13:08:12 -0600 > However this just seems to allow a card to decode multiple mac addresses > which in some oddball load balancing configurations may actually be > useful, but it seems fairly limited. > > Do you have a specific use case you envision for this multiple mac > functionality? Virtualization. If you can't tell the ethernet card that more than 1 MAC address are for it, you have to turn the thing into promiscuous mode. Networking on virtualization is typically done by giving each guest a unique MAC address, the guests have a virtual network device that connects to the control node (or dom0 in Xen parlace) and/or other guests. The control node has a switch that routes the packets from the guests either to other guests or out the real ethernet interface. Each guest gets a unique MAC so that the switch can know which guest an incoming packet is for.