From owner-freebsd-net@FreeBSD.ORG Wed Apr 30 18:02:06 2008 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id CC2B5106566C for ; Wed, 30 Apr 2008 18:02:06 +0000 (UTC) (envelope-from bms@FreeBSD.org) Received: from out4.smtp.messagingengine.com (out4.smtp.messagingengine.com [66.111.4.28]) by mx1.freebsd.org (Postfix) with ESMTP id 982B78FC17 for ; Wed, 30 Apr 2008 18:02:06 +0000 (UTC) (envelope-from bms@FreeBSD.org) Received: from compute2.internal (compute2.internal [10.202.2.42]) by out1.messagingengine.com (Postfix) with ESMTP id 47325E427D; Wed, 30 Apr 2008 14:02:06 -0400 (EDT) Received: from heartbeat1.messagingengine.com ([10.202.2.160]) by compute2.internal (MEProxy); Wed, 30 Apr 2008 14:02:06 -0400 X-Sasl-enc: aMbGEFoXUAb4/l8zWABRx+R548Ga8aP/uGBH/5+mQ0au 1209578525 Received: from empiric.lon.incunabulum.net (82-35-112-254.cable.ubr07.dals.blueyonder.co.uk [82.35.112.254]) by mail.messagingengine.com (Postfix) with ESMTPSA id 6EEB61781F; Wed, 30 Apr 2008 14:02:05 -0400 (EDT) Message-ID: <4818B41C.3090500@FreeBSD.org> Date: Wed, 30 Apr 2008 19:02:04 +0100 From: "Bruce M. Simpson" User-Agent: Thunderbird 2.0.0.12 (X11/20080423) MIME-Version: 1.0 To: Bakul Shah References: <20080430172705.2E3275AD6@mail.bitblocks.com> <4818B2B7.2070401@FreeBSD.org> In-Reply-To: <4818B2B7.2070401@FreeBSD.org> X-Enigmail-Version: 0.95.6 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: FreeBSD Net , Julian Elischer , Kevin Oberman Subject: Re: multiple routing tables review patch ready for simple testing. X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 30 Apr 2008 18:02:06 -0000 Bruce M. Simpson wrote: >> >> Wouldn't it make sense to treat each alias as on a separate >> logical interface? Then each logical interface belongs to >> exactly one FIB. On input you decide which logical inteface >> a packet arrived on by looking at its destination MAC >> address. That reduces confusion quite a bit, at least in my >> mind! What does doing more than this buy you? >> > > It doesn't buy anything because there is still no 1:1 mapping -- the > link-layer destination address maps to an ifp, and multiple aliases > exist on the ifp. Let me qualify that further: You are talking about splitting network layer addresses onto their own logical interfaces, with the goal of having a 1:1 mapping for FIB resolution. This doesn't buy anything, because in IP, the previous hop never encodes the next-hop address it sends to -- it merely performs a lookup and forwards to you; your MAC address is the same for every IP address you have on the link, therefore it is not a unique identifier. UNLESS you use a separate MAC address for every IP alias which you add, in which case, you are merely pushing the mapping elsewhere in the stack; it actually adds more complexity in this case.