Date: Mon, 19 Aug 2002 17:16:23 +0200 From: Jesper Skriver <jesper@FreeBSD.org> To: Jeff Behl <jeff@expertcity.com> Cc: net@freebsd.org Subject: Re: MTU not working? Message-ID: <20020819151623.GD48757@FreeBSD.org> In-Reply-To: <3D585310.8010709@expertcity.com> References: <3D585310.8010709@expertcity.com>
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On Mon, Aug 12, 2002 at 05:30:08PM -0700, Jeff Behl wrote: > We're seeing something odd that is seriously impacting our service for > some clients. Even though a the box seems to have the correct MTU in > the routing table, it doesn't seem to follow it in all cases. > > dell350-12.snv#sysctl -a | grep mtu > net.inet.tcp.path_mtu_discovery: 1 > > dell350-12.snv#uname -a > FreeBSD dell350-12.snv 4.4-RELEASE FreeBSD 4.4-RELEASE #0: Fri Aug 2 > 03:24:36 PDT 2002 > root@dell350-12.snv:/usr/src/sys/compile/COMMS44-2 i386 > > > dell350-12.snv#netstat -rnal | grep 10.4.1.134 > 10.4.1.134 63.xxx.224.129 UGHW 1 2268 1420 fxp0 > > > but tcpdump shows: > > > 17:21:43.497275 63.xxx.224.154.80 > 10.4.1.134.2314: . 1:1461(1460) ack > 248 win 17520 (DF) > 17:21:51.497212 63.xxx.224.154.80 > 10.4.1.134.2314: . 1:1461(1460) ack > 248 win 17520 (DF) > 17:22:07.497065 63.xxx.224.154.80 > 10.4.1.134.2314: . 1:1461(1460) ack > 248 win 17520 (DF) > > > obviosly the packet isn't making it back to the client as it's too big. > any ideas? I don't see any bug reports on it. We believe the same > situation exsits with a 4.6 server but I haven't checked that thorougly > enough yet. It's most likely a firewall or router filter, that block the ICMP messages coming back to your server. /Jesper -- Jesper Skriver, jesper(at)skriver(dot)dk - CCIE #5456 Senior network engineer @ AS3292, TDC Tele Danmark One Unix to rule them all, One Resolver to find them, One IP to bring them all and in the zone to bind them. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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