From owner-freebsd-questions@FreeBSD.ORG Tue Jan 17 00:28:31 2012 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id AA1E31065678 for ; Tue, 17 Jan 2012 00:28:31 +0000 (UTC) (envelope-from public@macfreek.nl) Received: from aphrodite.kinkhorst.nl (aphrodite.kinkhorst.nl [IPv6:2001:888:214f::f4]) by mx1.freebsd.org (Postfix) with ESMTP id 439AB8FC13 for ; Tue, 17 Jan 2012 00:28:31 +0000 (UTC) Received: from saramac0003.local (wolfje.macfreek.nl [145.99.1.66]) by aphrodite.kinkhorst.nl (Postfix) with ESMTPSA id 7451E1760FC; Tue, 17 Jan 2012 01:28:29 +0100 (CET) Message-ID: <4F14C0A7.4060505@macfreek.nl> Date: Tue, 17 Jan 2012 01:28:23 +0100 From: Freek Dijkstra User-Agent: Postbox 2.1.4 (Macintosh/20110308) MIME-Version: 1.0 To: freebsd-questions@freebsd.org References: <4F12F04B.2080504@macfreek.nl> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: Matt Mullins Subject: Re: Disable auto_linklocal X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 17 Jan 2012 00:28:31 -0000 Matt Mullins wrote: >> The link-local addresses don't really harm, but I found them confusing, >> as the host is running as a router, and rtadv announces the link-local >> address by default. > > IPv6-standards-wise, this is the correct thing to do. Router > advertisements should contain link-local source addresses and > advertise the link-local address as the router; the globally-routable > prefix that is being advertised is a completely different field in > those messages. Hi Matt, Thanks for the info. I figured out as much. It is not possible to turn of link-local addresses in FreeBSD 9. Neither sysctl net.inet6.ip6.auto_linklocal=0 nor ifconfig em0 inet6 -auto_linklocal has any effect. The man page for ifconfig explicitly states that removing the link-local IPv6 address may result in unexpected behaviour The good news is that it *is* possible to use the global scope IPv6 address in router advertisements. RFC 4861, as you mentioned, defines a prefix. However, RFC 6275 alters the property of that field if a new flag, the router address flag, is set. In that case, the prefix field can contain the actual IPv6 address of the router. Apparently, this is needed for mobile IP. Unfortunately rtadvd (the default BSD router advertisement daemon) does not support this R-flag. The radvd daemon (available in a port) does support this bit by setting: AdvRouterAddr on Wireshark show that indeed this works. Unfortunately, most of my clients on the network still don't understand this bit, so it seems that after all I just have to remember the link-local IP addresses next to the global scope IP addresses for my network. Oh well, they say it's good to train one's memory :) Freek