From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jay Cliburn Subject: Via Velocity minimum MTU size Date: Sun, 21 May 2006 21:56:49 -0500 Message-ID: <1148266609.2329.16.camel@osprey.hogchain.net> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: Received: from imf18aec.mail.bellsouth.net ([205.152.59.66]:53475 "EHLO imf18aec.mail.bellsouth.net") by vger.kernel.org with ESMTP id S964990AbWEVC4w (ORCPT ); Sun, 21 May 2006 22:56:52 -0400 Received: from ibm61aec.bellsouth.net ([74.227.55.112]) by imf18aec.mail.bellsouth.net with ESMTP id <20060522025651.ULCV28780.imf18aec.mail.bellsouth.net@ibm61aec.bellsouth.net> for ; Sun, 21 May 2006 22:56:51 -0400 Received: from [192.168.1.3] (really [74.227.55.112]) by ibm61aec.bellsouth.net with ESMTP id <20060522025650.ECTL4087.ibm61aec.bellsouth.net@[192.168.1.3]> for ; Sun, 21 May 2006 22:56:50 -0400 To: netdev@vger.kernel.org Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org Hello, I was advised by someone on the fedora-devel-list to post my question here. I'm trying to set the MTU size on my Via Velocity 6122 Gbit adapter from the default of 1500 down to 1492, but I keep getting this error: [root@osprey ~]# ifconfig eth0 mtu 1492 SIOCSIFMTU: Invalid argument Turns out that via-velocity.h defines the minimum MTU at 1500 bytes. #define VELOCITY_MIN_MTU (1514-14) #define VELOCITY_MAX_MTU (9000) And via-velocity.c enforces the limit. if ((new_mtu < VELOCITY_MIN_MTU) || new_mtu > (VELOCITY_MAX_MTU)) { VELOCITY_PRT(MSG_LEVEL_ERR, KERN_NOTICE "%s: Invalid MTU.\n", vptr->dev->name); return -EINVAL; } This is an Abit AV8 motherboard with an Athlon64 3000+ cpu running Fedora Core 5, kernel 2.6.16-1.2111_FC5 x86_64. Can someone please explain why the driver might constrain the NIC to a minimum MTU size of 1500? Thanks, Jay