From owner-freebsd-bugs@FreeBSD.ORG Fri Jan 13 17:49:23 2012 Return-Path: Delivered-To: freebsd-bugs@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 5F4ED1065673 for ; Fri, 13 Jan 2012 17:49:23 +0000 (UTC) (envelope-from iordan@cdf.toronto.edu) Received: from smtp.cdf.toronto.edu (penguin.cdf.utoronto.ca [128.100.31.106]) by mx1.freebsd.org (Postfix) with SMTP id 0D6528FC19 for ; Fri, 13 Jan 2012 17:49:22 +0000 (UTC) Received: (qmail 29406 invoked from network); 13 Jan 2012 12:22:41 -0500 Received: from australopithecus.cdf.toronto.edu (HELO ?128.100.31.7?) (iordan@128.100.31.7) by penguin.cdf.toronto.edu with SMTP; 13 Jan 2012 12:22:41 -0500 Message-ID: <4F106861.80507@cdf.toronto.edu> Date: Fri, 13 Jan 2012 12:22:41 -0500 From: Iordan Iordanov Organization: University Of Toronto User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.25) Gecko/20111213 Thunderbird/3.1.17 MIME-Version: 1.0 To: freebsd-bugs@freebsd.org Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: CDF Admin Subject: unable to set mtu 9000 on Intel x520-t2 adapter X-BeenThere: freebsd-bugs@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Bug reports List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 13 Jan 2012 17:49:23 -0000 Hello, We are testing FreeBSD 9.0-RELEASE on a pair of machines with 10GBASE-T Intel x520-t2 adapters interconnected with a straight-through cat6 rj45 cable. With mtu 1500, we are achieving aproximately 4 gigabits/s both directions as demonstrated with iperf. We wanted to test with mtu 9000 to see whether there would be any difference, but we encountered a problem setting it. We ran the following commands to alter the MTU to 9000 on the two machines (fw3 and fw4): fw3# ifconfig ix1 192.168.1.100 mtu 9000 fw4# ifconfig ix1 192.168.1.200 mtu 9000 However, instead of getting mtu set to 9000, what we see is the following message in the kernel output of both machines: ix1: Could not setup receive structures ix1: Could not setup receive structures and no traffic getting through. The moment we run: fw3# ifconfig ix1 192.168.1.100 mtu 1500 fw4# ifconfig ix1 192.168.1.200 mtu 1500 we see: ix1: link state changed to DOWN ix1: link state changed to UP and traffic starts getting through as before. More information about our hardware is: Motherboard: Supermicro H8DGU-F CPU: AMD 6128 8-core Memory: 16GB DDR3 NICs: Intel x520-t2 10GbaseT adapters An ifconfig ix1 output for one of the machines: fw4# ifconfig ix1 ix1: flags=8843 metric 0 mtu 1500 options=401bb ether 00:1b:21:d6:19:51 inet 192.168.1.200 netmask 0xffffff00 broadcast 192.168.1.255 nd6 options=29 media: Ethernet autoselect (autoselect ) status: active Many thanks for any help/action on this! Sincerely, Iordan Iordanov CDF System Administrator University of Toronto