From owner-freebsd-questions@FreeBSD.ORG Mon Aug 30 09:53:50 2004 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 072AA16A4CE for ; Mon, 30 Aug 2004 09:53:50 +0000 (GMT) Received: from out008.verizon.net (out008pub.verizon.net [206.46.170.108]) by mx1.FreeBSD.org (Postfix) with ESMTP id 7715A43D31 for ; Mon, 30 Aug 2004 09:53:49 +0000 (GMT) (envelope-from skip.ford@verizon.net) Received: from pool-70-17-33-17.pskn.east.verizon.net ([70.17.33.17]) by out008.verizon.netESMTP <20040830095348.WMJY8960.out008.verizon.net@pool-70-17-33-17.pskn.east.verizon.net> for ; Mon, 30 Aug 2004 04:53:48 -0500 Date: Mon, 30 Aug 2004 05:53:47 -0400 From: Skip Ford To: freebsd-questions@FreeBSD.org Message-ID: <20040830095347.GC587@lucy.pool-70-17-33-17.pskn.east.verizon.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.4.2.1i X-Authentication-Info: Submitted using SMTP AUTH at out008.verizon.net from [70.17.33.17] at Mon, 30 Aug 2004 04:53:48 -0500 Subject: Per-route MTU? X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 30 Aug 2004 09:53:50 -0000 When specifying the MTU of a route, packets larger than the MTU are still sent... $ route -n get 10.10.6.1 route to: 10.10.6.1 destination: default mask: default gateway: 192.168.1.1 interface: ed0 flags: recvpipe sendpipe ssthresh rtt,msec rttvar hopcount mtu expire 0 0 0 0 0 0 1492 0 $ sudo ping -D -n -c 1 -s 1472 10.10.6.1 PING 10.10.6.1 (10.10.6.1): 1472 data bytes 36 bytes from 192.168.1.1: frag needed and DF set (MTU 1492) Vr HL TOS Len ID Flg off TTL Pro cks Src Dst 4 5 00 dc05 e586 0 0000 40 01 7de5 192.168.1.2 10.10.6.1 --- 10.10.6.1 ping statistics --- 1 packets transmitted, 0 packets received, 100% packet loss Why doesn't this host recognize that 1500 is too large of a packet to send to the default destination based on the MTU of the route being 1492? Am I doing something wrong?...or misunderstanding something? $ uname -r 6.0-CURRENT $ sysctl -a | grep mtu net.inet.tcp.path_mtu_discovery: 1 The route's MTU was set using "-lock -mtu 1492". -- Skip