From mboxrd@z Thu Jan 1 00:00:00 1970 From: YOSHIFUJI Hideaki Subject: Re: Why are IPv6 host and anycast routes referencing lo device? Date: Tue, 8 Nov 2016 11:26:34 +0900 Message-ID: <14a4ccfb-11d9-f96b-a741-c8595b81ca45@miraclelinux.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: hideaki.yoshifuji@miraclelinux.com To: David Ahern , Hannes Frederic Sowa , "netdev@vger.kernel.org" Return-path: Received: from mail-pf0-f173.google.com ([209.85.192.173]:34340 "EHLO mail-pf0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752693AbcKHC0i (ORCPT ); Mon, 7 Nov 2016 21:26:38 -0500 Received: by mail-pf0-f173.google.com with SMTP id n85so99250832pfi.1 for ; Mon, 07 Nov 2016 18:26:37 -0800 (PST) In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: Hi, David Ahern wrote: > > Can anyone explain why host routes and anycast routes for IPv6 are added with the device set to loopback versus the device with the address: > > local ::1 dev lo proto none metric 0 pref medium > local 2000:1:: dev lo proto none metric 0 pref medium > local 2000:1::3 dev lo proto none metric 0 pref medium > local 2100:2:: dev lo proto none metric 0 pref medium > local 2100:2::3 dev lo proto none metric 0 pref medium > > > This behavior differs from IPv4 where host routes use the device with the address: > > broadcast 10.1.1.0 dev eth0 proto kernel scope link src 10.1.1.3 > local 10.1.1.3 dev eth0 proto kernel scope host src 10.1.1.3 > broadcast 10.1.1.255 dev eth0 proto kernel scope link src 10.1.1.3 > broadcast 10.100.2.0 dev eth2 proto kernel scope link src 10.100.2.3 > local 10.100.2.3 dev eth2 proto kernel scope host src 10.100.2.3 > broadcast 10.100.2.255 dev eth2 proto kernel scope link src 10.100.2.3 > > The use of loopback pre-dates the git history, so wondering if someone recalls the reason why. We would like to change that to make it consistent with IPv4 - with a sysctl to maintain backwards compatibility. Once I tried I did not work. You could try again to see what happens. --yoshfuji > > Thanks, > David > -- Hideaki Yoshifuji Technical Division, MIRACLE LINUX CORPORATION