From owner-freebsd-net@FreeBSD.ORG Fri Jun 1 16:19:49 2012 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id B66F0106566C for ; Fri, 1 Jun 2012 16:19:49 +0000 (UTC) (envelope-from jeffrey.e.pieper@intel.com) Received: from mga02.intel.com (mga02.intel.com [134.134.136.20]) by mx1.freebsd.org (Postfix) with ESMTP id 874378FC17 for ; Fri, 1 Jun 2012 16:19:49 +0000 (UTC) Received: from orsmga001.jf.intel.com ([10.7.209.18]) by orsmga101.jf.intel.com with ESMTP; 01 Jun 2012 09:19:49 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.67,352,1309762800"; d="scan'208";a="147077103" Received: from orsmsx606.amr.corp.intel.com ([10.22.226.128]) by orsmga001.jf.intel.com with ESMTP; 01 Jun 2012 09:19:49 -0700 Received: from orsmsx105.amr.corp.intel.com (10.22.225.132) by orsmsx606.amr.corp.intel.com (10.22.226.128) with Microsoft SMTP Server (TLS) id 8.2.255.0; Fri, 1 Jun 2012 09:19:48 -0700 Received: from orsmsx101.amr.corp.intel.com ([169.254.8.121]) by ORSMSX105.amr.corp.intel.com ([169.254.4.232]) with mapi id 14.01.0355.002; Fri, 1 Jun 2012 09:19:48 -0700 From: "Pieper, Jeffrey E" To: John-Mark Gurney , "Bjoern A. Zeeb" Thread-Topic: if_em and large mtu bug? Thread-Index: AQHNPlFCv5wZkRdS2EOB3+G/DquDa5biqYcAgAC1lQCAAh/GgIAAKA2g Date: Fri, 1 Jun 2012 16:19:47 +0000 Message-ID: <2A35EA60C3C77D438915767F458D6568481AA470@ORSMSX101.amr.corp.intel.com> References: <4FC5FA0B.5010609@cran.org.uk> <4FC6062A.3010002@rdtc.ru> <20120601065219.GF91292@funkthat.com> In-Reply-To: <20120601065219.GF91292@funkthat.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.22.254.139] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 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 16:19:49 -0000 -----Original Message----- From: owner-freebsd-net@freebsd.org [mailto:owner-freebsd-net@freebsd.org] = On Behalf Of John-Mark Gurney Sent: Thursday, May 31, 2012 11:52 PM To: Bjoern A. Zeeb Cc: freebsd-net@freebsd.org Subject: Re: if_em and large mtu bug? 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: >=20 > > 30.05.2012 17:44, Bruce Cran ??????????: > >> Are there any known problems with if_em and jumbo packets? I've found= =20 > >> that my ssh connection breaks (when running dmesg etc.) if I configure= =20 > >> the mtu to 9216 via rc.conf - but if I initially use a 1500 byte mtu a= nd=20 > >> then manually configure it to 9216 then no problems occur. > >>=20 >=20 > 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 mt= u, > 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... --=20 John-Mark Gurney Voice: +1 415 225 5579 "All that I will do, has been done, All that I have, has not." This is what I use (I'm JFV's validation engineer): Ifconfig emX mtu =20 Doing this adds it to the routing table and seems to avoid any issues.=20 I hope this helps, Jeff _______________________________________________ freebsd-net@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-net To unsubscribe, send any mail to "freebsd-net-unsubscribe@freebsd.org"