From owner-freebsd-net@FreeBSD.ORG Fri Jun 1 07:12:49 2012 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id 59CAC10656F7 for ; Fri, 1 Jun 2012 07:12:49 +0000 (UTC) (envelope-from jmg@h2.funkthat.com) Received: from h2.funkthat.com (gate2.funkthat.com [208.87.223.18]) by mx1.freebsd.org (Postfix) with ESMTP id 32D1E8FC0C for ; Fri, 1 Jun 2012 07:12:49 +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 q516qLri053013 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Thu, 31 May 2012 23:52:21 -0700 (PDT) (envelope-from jmg@h2.funkthat.com) Received: (from jmg@localhost) by h2.funkthat.com (8.14.3/8.14.3/Submit) id q516qJtl053012; Thu, 31 May 2012 23:52:19 -0700 (PDT) (envelope-from jmg) Date: Thu, 31 May 2012 23:52:19 -0700 From: John-Mark Gurney To: "Bjoern A. Zeeb" Message-ID: <20120601065219.GF91292@funkthat.com> Mail-Followup-To: "Bjoern A. Zeeb" , freebsd-net@freebsd.org References: <4FC5FA0B.5010609@cran.org.uk> <4FC6062A.3010002@rdtc.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.3i X-Operating-System: FreeBSD 7.2-RELEASE i386 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-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.2.2 (h2.funkthat.com [127.0.0.1]); Thu, 31 May 2012 23:52:21 -0700 (PDT) Cc: freebsd-net@freebsd.org Subject: Re: if_em and large mtu bug? X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 01 Jun 2012 07:12:49 -0000 Bjoern A. Zeeb wrote this message on Wed, May 30, 2012 at 22:26 +0000: > On 30. May 2012, at 11:36 , Eugene Grosbein wrote: > > > 30.05.2012 17:44, Bruce Cran ??????????: > >> Are there any known problems with if_em and jumbo packets? I've found > >> that my ssh connection breaks (when running dmesg etc.) if I configure > >> the mtu to 9216 via rc.conf - but if I initially use a 1500 byte mtu and > >> then manually configure it to 9216 then no problems occur. > >> > > That is due to another known bug; > if you check netstat -rn and the mtu there on your routes you'll figure. > if you remove your addresses/routes and re-add them after changing the mtu, > you'll see it as well. Just to comment, this isn't a bug.. it's that FreeBSD allows you to control the mtu to a host via the routing table... Previously it would always max out the routes MTU meaning that you could never reduce the MTU to a problematic host, while keeping the mtu larger for others i.e. have a mixed network w/ jumbo and normal frames... -- John-Mark Gurney Voice: +1 415 225 5579 "All that I will do, has been done, All that I have, has not."