From owner-freebsd-net@FreeBSD.ORG  Thu Apr 17 17:50:34 2003
Return-Path: <owner-freebsd-net@FreeBSD.ORG>
Delivered-To: freebsd-net@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP
	id E1F0A37B401; Thu, 17 Apr 2003 17:50:34 -0700 (PDT)
Received: from khavrinen.lcs.mit.edu (khavrinen.lcs.mit.edu [18.24.4.193])
	by mx1.FreeBSD.org (Postfix) with ESMTP
	id E2A3443FA3; Thu, 17 Apr 2003 17:50:31 -0700 (PDT)
	(envelope-from wollman@khavrinen.lcs.mit.edu)
Received: from khavrinen.lcs.mit.edu (localhost [IPv6:::1])
	by khavrinen.lcs.mit.edu (8.12.9/8.12.9) with ESMTP id h3I0oUmA033278
	(version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK);
	Thu, 17 Apr 2003 20:50:31 -0400 (EDT)
	(envelope-from wollman@khavrinen.lcs.mit.edu)
Received: (from wollman@localhost)
	by khavrinen.lcs.mit.edu (8.12.9/8.12.9/Submit) id h3I0oUbg033275;
	Thu, 17 Apr 2003 20:50:30 -0400 (EDT)
	(envelope-from wollman)
Date: Thu, 17 Apr 2003 20:50:30 -0400 (EDT)
From: Garrett Wollman <wollman@lcs.mit.edu>
Message-Id: <200304180050.h3I0oUbg033275@khavrinen.lcs.mit.edu>
To: Brooks Davis <brooks@one-eyed-alien.net>
In-Reply-To: <20030418001904.GA23983@Odin.AC.HMC.Edu>
References: <16031.17219.159093.279782@canoe.velocet.net>
	<20030418001904.GA23983@Odin.AC.HMC.Edu>
cc: freebsd-net@freebsd.org
cc: freebsd-stable@freebsd.org
Subject: Re: vlan0 on em0 has mtu 1496
X-BeenThere: freebsd-net@freebsd.org
X-Mailman-Version: 2.1.1
Precedence: list
List-Id: Networking and TCP/IP with FreeBSD <freebsd-net.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-net>,
	<mailto:freebsd-net-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-net>
List-Post: <mailto:freebsd-net@freebsd.org>
List-Help: <mailto:freebsd-net-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-net>,
	<mailto:freebsd-net-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Fri, 18 Apr 2003 00:50:35 -0000

<<On Thu, 17 Apr 2003 17:19:04 -0700, Brooks Davis <brooks@one-eyed-alien.net> said:

> Because the vlan header takes up 4 bytes.  With em(4) devices it looks
> like fixing that should be a simple matter of raising the real
> interface's MTU to 1504.

Actually, the parent interface's MTU should not be touched.  The
link-layer header length is what needs to be increased.

-GAWollman