From owner-freebsd-hackers Wed Dec 2 09:07:02 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id JAA13463 for freebsd-hackers-outgoing; Wed, 2 Dec 1998 09:07:02 -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 JAA13343 for ; Wed, 2 Dec 1998 09:04:55 -0800 (PST) (envelope-from ru@ucb.crimea.ua) Received: (from ru@localhost) by relay.ucb.crimea.ua (8.8.8/8.8.8) id SAA05942; Wed, 2 Dec 1998 18:58:08 +0200 (EET) (envelope-from ru) Date: Wed, 2 Dec 1998 18:58:08 +0200 From: Ruslan Ermilov To: Thomas David Rivers Cc: eischen@vigrid.com, nate@mt.sri.com, dillon@apollo.backplane.com, hackers@FreeBSD.ORG, luigi@labinfo.iet.unipi.it Subject: Re: TCP bug Message-ID: <19981202185808.A4604@ucb.crimea.ua> Mail-Followup-To: Thomas David Rivers , eischen@vigrid.com, nate@mt.sri.com, dillon@apollo.backplane.com, hackers@FreeBSD.ORG, luigi@labinfo.iet.unipi.it References: <199812021636.JAA06068@mt.sri.com> <199812021647.LAA09094@lakes.dignus.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Mailer: Mutt 0.94.17i In-Reply-To: <199812021647.LAA09094@lakes.dignus.com>; from Thomas David Rivers on Wed, Dec 02, 1998 at 11:47:03AM -0500 X-Operating-System: FreeBSD 2.2.7-STABLE i386 Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG On Wed, Dec 02, 1998 at 11:47:03AM -0500, Thomas David Rivers wrote: > > Just to add to this; I've got exactly the same symptoms; which I previously > reported. > > On my internal network; I can't get to some sites (www.aol.com being > the best example.) > > But, If I'm on the gateway machine - it has no problems getting there. > > Thus, I was implicating natd. > > And - it so happens; my connection is a SL/IP connection, and my MTU > is 552. > > I'm betting there's something going on with natd and packet fragmentation. > > Several people unsuccessfully tried to duplicate my problem; but I'm > wondering now if they were using PPP or something else that had a higher > MTU, and, thus, didn't fragment any packets. > > - Dave Rivers - Some sites block ICMP and thus break PMTU discovery. You can work around this problem by disabling PMTU discovery on all your FreeBSD boxes. This is done by locking MTU on route. I use: route change default -mtu 1500 (for Ethernet) route change default -mtu 552 (for SLIP) After this everything works fine even with sites that block ICMP. I had this problem some time ago, when Hub.FreeBSD.org was blocking ICMP. -- 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