From owner-freebsd-net@FreeBSD.ORG Tue Aug 20 01:14:52 2013 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTP id 1807471F for ; Tue, 20 Aug 2013 01:14:52 +0000 (UTC) (envelope-from jmg@h2.funkthat.com) Received: from h2.funkthat.com (gate2.funkthat.com [208.87.223.18]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id ED19124E3 for ; Tue, 20 Aug 2013 01:14:51 +0000 (UTC) Received: from h2.funkthat.com (localhost [127.0.0.1]) by h2.funkthat.com (8.14.3/8.14.3) with ESMTP id r7K0wmtH037642 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Mon, 19 Aug 2013 17:58:48 -0700 (PDT) (envelope-from jmg@h2.funkthat.com) Received: (from jmg@localhost) by h2.funkthat.com (8.14.3/8.14.3/Submit) id r7K0wl1e037641; Mon, 19 Aug 2013 17:58:47 -0700 (PDT) (envelope-from jmg) Date: Mon, 19 Aug 2013 17:58:47 -0700 From: John-Mark Gurney To: Joe Holden Subject: Re: Updating route MTU when interface changes Message-ID: <20130820005847.GY94127@funkthat.com> Mail-Followup-To: Joe Holden , freebsd-net@freebsd.org References: <520B8694.1050407@rewt.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <520B8694.1050407@rewt.org.uk> User-Agent: Mutt/1.4.2.3i X-Operating-System: FreeBSD 7.2-RELEASE i386 X-PGP-Fingerprint: 54BA 873B 6515 3F10 9E88 9322 9CB1 8F74 6D3F A396 X-Files: The truth is out there X-URL: http://resnet.uoregon.edu/~gurney_j/ X-Resume: http://resnet.uoregon.edu/~gurney_j/resume.html X-to-the-FBI-CIA-and-NSA: HI! HOW YA DOIN? can i haz chizburger? X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.2 (h2.funkthat.com [127.0.0.1]); Mon, 19 Aug 2013 17:58:48 -0700 (PDT) Cc: freebsd-net@freebsd.org 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: Tue, 20 Aug 2013 01:14:52 -0000 Joe Holden wrote this message on Wed, Aug 14, 2013 at 14:31 +0100: > I noticed this some years ago but I just checked and its still there - > when the mtu of an interface is changed, any routes (eg connected route) > using that interface aren't updated until the interface is shut/unshut - > is this by design or is it an oversight? Having to down/up remote > machine interfaces that are potentially forwarding traffic just to > change the mtu seems silly. FreeBSD used to have code that would automaticly increase a route's MTU to the largest that the interface provided... This is an issue if you want to support a mixed MTU lan... You can no longer administrivally restirct the size of packets being sent out... The other option is to simply delete all the host routes for that interface and change the net route, and things will be what you expect.. -- John-Mark Gurney Voice: +1 415 225 5579 "All that I will do, has been done, All that I have, has not."