From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ben Greear Subject: Re: Interface without IP address can route?? Date: Wed, 24 Aug 2011 09:20:10 -0700 Message-ID: <4E5524BA.3070303@candelatech.com> References: <4E5443CD.60502@candelatech.com> <1314190890.25967.114.camel@mojatatu> <4E54FBA6.6090905@candelatech.com> <20110824161557.GC611458@jupiter.n2.diac24.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: jhs@mojatatu.com, jamal , netdev To: David Lamparter Return-path: Received: from mail.candelatech.com ([208.74.158.172]:60644 "EHLO ns3.lanforge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751655Ab1HXQU5 (ORCPT ); Wed, 24 Aug 2011 12:20:57 -0400 In-Reply-To: <20110824161557.GC611458@jupiter.n2.diac24.net> Sender: netdev-owner@vger.kernel.org List-ID: On 08/24/2011 09:15 AM, David Lamparter wrote: > On Wed, Aug 24, 2011 at 06:24:54AM -0700, Ben Greear wrote: >> On 08/24/2011 06:01 AM, jamal wrote: >>> It makes sense to behave this way. >>> IPv4 addresses are owned by the system not interfaces. >>> If you want to control the forwarding behavior, control ARP so it doesnt >>> respond on the interfaces with no IP. > > I agree. > >> I understand your argument about IPs being owned by system instead of >> interface, but I think it's the wrong behaviour in this case. Can >> you think of any case where this behaviour actually helps? > > It's used for oddball /32 setups at server hosting farms that look like: > /--- eth0, no ip ---- server 0.1.4.5/32, default via 0.1.2.3 > router --- eth1, no ip ---- server 0.1.6.7/32, default via 0.1.2.3 > \--- eth2, no ip ---- server 0.1.8.9/32, default via 0.1.2.3 > \- eth3: 0.1.2.3/28 - to rest of internet > > The general idea is to a) conserve IPs and b) not renumber servers even > when they move, so you end up with random scattered /32s on the servers > and the router has no sensible IP. > >> Either way, it appears I can work around this by explicitly disabling >> forwarding for this particular interface. > > I was about to suggest exactly this :) Ok..glad to know there are folks with even crazier setups than mine :) Thanks, Ben -- Ben Greear Candela Technologies Inc http://www.candelatech.com