From owner-freebsd-net@FreeBSD.ORG Wed Oct 29 09:34:47 2008 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 DD86B1065680 for ; Wed, 29 Oct 2008 09:34:47 +0000 (UTC) (envelope-from eitans@mellanox.co.il) Received: from mellanox.co.il (mail.mellanox.co.il [194.90.237.43]) by mx1.freebsd.org (Postfix) with ESMTP id 24B978FC0C for ; Wed, 29 Oct 2008 09:34:46 +0000 (UTC) (envelope-from eitans@mellanox.co.il) Received: from Internal Mail-Server by MTLPINE1 (envelope-from eitans@mellanox.co.il) with SMTP; 29 Oct 2008 11:34:43 +0200 X-MimeOLE: Produced By Microsoft Exchange V6.5 Content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Date: Wed, 29 Oct 2008 11:34:35 +0200 Message-ID: <5D49E7A8952DC44FB38C38FA0D758EADD00926@mtlexch01.mtl.com> In-Reply-To: <20081028210215.GE51033@funkthat.com> X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: It seems that FreeBSD-7.0 does not use the available MTU Thread-Index: Ack5QHcZTu/n8YvdQf2SMre0YlS/FgAZ0eBg References: <5D49E7A8952DC44FB38C38FA0D758EADC72E72@mtlexch01.mtl.com> <5D49E7A8952DC44FB38C38FA0D758EADCC5FB7@mtlexch01.mtl.com> <20081028210215.GE51033@funkthat.com> From: "Eitan Shefi" To: "John-Mark Gurney" Cc: freebsd-net@freebsd.org Subject: RE: It seems that FreeBSD-7.0 does not use the available MTU 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: Wed, 29 Oct 2008 09:34:48 -0000 This is indeed the problem, thanks. Is this a known issue with FreeBSD-7.0 ? I do not want to hide a potential bug in the NIC driver. Eitan Shefi -----Original Message----- From: John-Mark Gurney [mailto:jmg@funkthat.com]=20 Sent: Tuesday, October 28, 2008 11:02 PM To: Eitan Shefi Cc: freebsd-net@freebsd.org Subject: Re: It seems that FreeBSD-7.0 does not use the available MTU Eitan Shefi wrote this message on Mon, Oct 27, 2008 at 23:53 +0200: > I am using 2 hosts with FreeBSD-7.0 connected directly. > When I change the MTU to a value greater then 1500, for example 3000,=20 > and then send "ping" with message size 2500, from one host to the=20 > other, the other host gets more then one ICMP packet, even thaw the=20 > message that was send is match smaller then the MTU. > =20 > I tried to run this test using a different NIC, but I got the same=20 > behavior. > =20 > I run: > 1. On both hosts: > ifconfig mtnic0 mtu 3000 > 2. Than on one host I run: > tcpdump -i mtnic0 icmp > 3. And on the other host I run: > ping -s 2500 -c 1 OTHER_HOST_IP (ping to "mtnic0" on the other > host) run netstat -rnW to see what the route's MTU is. Most likely you need to set the mtu before you configure an ip address on the interface so that the network's route is created w/ the correct MTU... either readd the network route, or change the mtu of the route for the host: route change -mtu 3000 OTHER_HOST_IP also change it on the network route so that when the host route gets flushed and recreated it will be created w/ the correct MTU... --=20 John-Mark Gurney Voice: +1 415 225 5579 "All that I will do, has been done, All that I have, has not."