From owner-freebsd-hackers Mon Dec 7 08:53:33 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id IAA17765 for freebsd-hackers-outgoing; Mon, 7 Dec 1998 08:53:33 -0800 (PST) (envelope-from owner-freebsd-hackers@FreeBSD.ORG) Received: from relay.ucb.crimea.ua (relay.ucb.crimea.ua [194.93.177.113]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id IAA17607 for ; Mon, 7 Dec 1998 08:50:05 -0800 (PST) (envelope-from ru@ucb.crimea.ua) Received: (from ru@localhost) by relay.ucb.crimea.ua (8.8.8/8.8.8) id SAA09918; Mon, 7 Dec 1998 18:43:13 +0200 (EET) (envelope-from ru) Date: Mon, 7 Dec 1998 18:43:12 +0200 From: Ruslan Ermilov To: Thomas David Rivers Cc: hackers@FreeBSD.ORG Subject: Re: TCP bug Message-ID: <19981207184312.A7011@ucb.crimea.ua> Mail-Followup-To: Thomas David Rivers , hackers@FreeBSD.ORG References: <19981207175804.A1183@ucb.crimea.ua> <199812071611.LAA01157@lakes.dignus.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Mailer: Mutt 0.94.17i In-Reply-To: <199812071611.LAA01157@lakes.dignus.com>; from Thomas David Rivers on Mon, Dec 07, 1998 at 11:11:16AM -0500 X-Operating-System: FreeBSD 2.2.7-STABLE i386 Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG On Mon, Dec 07, 1998 at 11:11:16AM -0500, Thomas David Rivers wrote: > > Umm. Have you tried to disable PMTU on your FreeBSD box? > > > > Nope.. do you mean on the interior nodes or the gateway - or both? > (Some of my interior nodes aren't FreeBSD... so I may not have that option.) > I mean the FreeBSD box you are sitting on and from which you can't access www.aol.com. > And, I thought I would find something about that in the sysctls - say, > net.inet.XXX - but nothing jumps out at me... which sysctl would disable > MTU-D? MTU can be disabled on per-route basis. It is neither clear, nor documented. This can be done by locking MTU on a route. For example, if you want to disable PMTU-D on default, you should say: # route change default -lock -mtu 1500 (or whatever you have it set to) ! Note, that if you specify -mtu without parameter (this is what came to my ! mind first), route command will coredump. Now, you should be able to check that PMTU-D is disabled by: a) ``route get default'' will show mtu as 1500L, i.e. 1500 and locked; b) ``route get www.aol.com'' will show the same mtu, because this route is cloned from the default (or maybe you have direct route to AOL?); c) ``tcpdump'' won't show DF bit in outgoing packets (this is for sure). BR, -- Ruslan Ermilov Sysadmin and DBA of the ru@ucb.crimea.ua United Commercial Bank +380.652.247.647 Simferopol, Ukraine http://www.FreeBSD.org The Power To Serve http://www.oracle.com Enabling The Information Age To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message