From owner-freebsd-net@FreeBSD.ORG Wed Mar 13 13:10:21 2013 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by hub.freebsd.org (Postfix) with ESMTP id 684D1BBA for ; Wed, 13 Mar 2013 13:10:21 +0000 (UTC) (envelope-from schrodinger@konundrum.org) Received: from crux.konundrum.org (crux.konundrum.org [IPv6:2001:41d0:1:c74c::1]) by mx1.freebsd.org (Postfix) with ESMTP id C9AD918A for ; Wed, 13 Mar 2013 13:10:20 +0000 (UTC) Received: from crux.konundrum.org (localhost [127.0.0.1]) by crux.konundrum.org (Postfix) with ESMTP id 347A11CD7F4 for ; Wed, 13 Mar 2013 13:10:19 +0000 (GMT) X-Virus-Scanned: amavisd-new at konundrum.org Received: from crux.konundrum.org ([127.0.0.1]) by crux.konundrum.org (crux.konundrum.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id Be5J22jIs5mB for ; Wed, 13 Mar 2013 13:10:18 +0000 (GMT) Received: from defiant.konundrum.org (defiant.konundrum.org [IPv6:2001:770:146:2::1]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by crux.konundrum.org (Postfix) with ESMTPS id 946931CD7F3 for ; Wed, 13 Mar 2013 13:10:18 +0000 (GMT) Received: from defiant.konundrum.org (localhost [127.0.0.1]) by defiant.konundrum.org (8.14.5/8.14.5) with ESMTP id r2DDAH50018989 for ; Wed, 13 Mar 2013 13:10:17 GMT (envelope-from schrodinger@konundrum.org) Received: (from schrodinger@localhost) by defiant.konundrum.org (8.14.5/8.14.5/Submit) id r2DDAHwU018988 for freebsd-net@freebsd.org; Wed, 13 Mar 2013 13:10:17 GMT (envelope-from schrodinger@konundrum.org) X-Authentication-Warning: defiant.konundrum.org: schrodinger set sender to schrodinger@konundrum.org using -f Date: Wed, 13 Mar 2013 13:10:17 +0000 From: Schrodinger To: freebsd-net@freebsd.org Subject: Re: ipv6 default router Operation not permitted Message-ID: <20130313131016.GE17859@defiant.konundrum.org> References: <20130312225018.GA13589@defiant.konundrum.org> <3ABB5AED-DEA9-42F6-82A1-FEA9E8BBBDCF@my.gd> <20130313091727.GA17859@defiant.konundrum.org> <201303131227.57751.Mark.Martinec+freebsd@ijs.si> <20130313125221.GD17859@defiant.konundrum.org> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="zjcmjzIkjQU2rmur" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.14 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, 13 Mar 2013 13:10:21 -0000 --zjcmjzIkjQU2rmur Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On 2013/03/13 14:02, Fleuriot Damien wrote: >=20 > On Mar 13, 2013, at 1:52 PM, Schrodinger wrot= e: >=20 > > On 2013/03/13 12:27, Mark Martinec wrote: > >=20 > > Hi Mark, > >=20 > >> On Wednesday March 13 2013 10:17:27 Schrodinger wrote: > >>> ifconfig_re0_ipv6=3D"inet6 2001:41D0:2:E7c4::1 prefixlen 64" > >>> [...] > >>> Voodoo, indeed... I'm sure there's a /48 used somewhere but to be more > >>> specific, or rather obvious, my default gateway resides at the bounda= ry > >>> of a /56 - 2001:41D0:2:E700::/56 > >>=20 > >> Having multiple IPv6 subnets on the same wire is asking for trouble. > >>=20 > >=20 > > This isn't my network so I don't have any input into the matter. This > > is the OVH configuration for their dedicated servers, at least in my > > product range. > >=20 > >> For example, I believe an ICMP redirect still (in 9.1) does not create > >> a temporary route: > >> http://www.freebsd.org/cgi/query-pr.cgi?pr=3D152791 > >> which beat us hard time (random unreachability between hosts), > >> having to rearrange that legacy segment which happened to have > >> two subnets on the same wire. > >>=20 > >> The static routes destinations must be directly reachable (on-link). > >>=20 > >=20 > > Does adding the interface route not put the default gateway on-link > > though ? > >=20 > >> Either use a single /56 for the whole LAN, adjusting the prefix > >> length on each interface, or provide a router within each subnet. > >>=20 > >=20 > > If I am to change my prefix length to /56 this means that anyone else in > > that /56 who is configured with a prefix length of 64 will be routing to > > me and I will be swicthing to them.... This could cause problems. >=20 >=20 > I fail to see how they would be routing to you and you would be switching= to them. >=20 >=20 > OVH allocates a /64 per customer. > To avoid having to setup 1 gateway per customer, they set up a single one= within a /56 , allowing for 256 /64s > This mimics the situation where your host gives you a /32 ipv4 withing a = /24 network and uses a single gateway, again for 250ish customers. >=20 > Whenever an IPv6 packet arrives on OVH's router for your /64, it is route= d to your server. > I don't see how this qualifies as "another customer routing to you" ? >=20 I am informed that I must configure my interface to /64 by OVH. The same as everyone else. So if everyone was on a /64 then we will send packets to each other via our shared default gateway. E.g.: I am 2001:41d0:2:e7c4::1/64 My default gateway is 2001:41d0:2:e7ff:ff:ff:ff:ff If I wanted to communicate with a host in 2001:41d0:2:e7c5::/64 and his default gateway is also 2001:41d0:2:e7ff:ff:ff:ff:ff then we will route packets to each other. Correct? If I were to change my interface prefix length to /56 my host would no longer consider the need to send packets to the default gateway for any host within this /56. I would simply perform Neighbour Solicitation on my link. E.g.: I am 2001:41d0:2:e7c4::1/56 My default gateway is 2001:41d0:2:e7ff:ff:ff:ff:ff If I wanted to communicate with a host in 2001:41d0:2:e7c5::/64 and his default gateway is also 2001:41d0:2:e7ff:ff:ff:ff:ff then I would switch to him because the /56 is "on-link" to me but to the recipient he must route to me via his default gateway. Correct? C. --=20 +---------------------------------------------------------------+ Quidquid latine dictum sit, altum sonatur. 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