From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andreas Hofmeister Subject: Subnet router anycast for FE80/10 ? Date: Mon, 31 Oct 2011 21:22:41 +0100 Message-ID: <4EAF0391.80907@collax.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit To: netdev@vger.kernel.org Return-path: Received: from mail.collax.com ([213.218.25.154]:54418 "EHLO mail.collax.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751964Ab1JaUWo (ORCPT ); Mon, 31 Oct 2011 16:22:44 -0400 Received: from localhost (mail.collax.com [127.0.0.1]) by localhost (Postfix) with ESMTP id 5F84B15F801C for ; Mon, 31 Oct 2011 21:22:42 +0100 (CET) Received: from mail.collax.com ([127.0.0.1]) by localhost (mail.collax.com [127.0.0.1]) (amavisd-new, port 10033) with ESMTP id TMjAxOjGZXgk for ; Mon, 31 Oct 2011 21:22:41 +0100 (CET) Received: from andinc.coreworks.de (unknown [172.16.1.3]) by mail.collax.com (Postfix) with ESMTPSA id 8FD2D15F801A for ; Mon, 31 Oct 2011 21:22:41 +0100 (CET) Sender: netdev-owner@vger.kernel.org List-ID: Hi, I noticed that once forwarding has been enabled on an interface, there is a "subnet router anycast address" for the link-local address prefix FE80/10. This address seems not to be explicitly mentioned in any RFC, but RFC 4291 says "All routers are required to support the Subnet-Router anycast addresses for the subnets to which they have interfaces." In the sense that a Linux router actually has an address FE80/10 on each ipv6 enabled interface, it seems to be correct to also have FE80:: as an anycast address on all interfaces which have ipv6 and forwarding enabled. But then, FE80/10 is not actually supposed to be routed at all and so a router cannot not really be a router for that particular subnet ? Or is "FE80::" just supposed to be the anycast equivalent for the "all routers" multicast address ff02::2 ? Maybe someone on this list could enlighten me. Ciao Andi