Date: Fri, 30 Nov 2001 00:56:39 -0500 From: "Matthew Emmerton" <matt@gsicomp.on.ca> To: "Matthew Emmerton" <matt@gsicomp.on.ca>, "Andre Oppermann" <oppermann@pipeline.ch>, <julian@elischer.org> Cc: <freebsd-net@FreeBSD.ORG> Subject: Re: Very strange network behaviour - can anyone help me analyse tcpdump output? Message-ID: <002b01c17963$c8df5fd0$1200a8c0@gsicomp.on.ca> References: <Pine.BSF.4.21.0111271041160.56896-100000@xena.gsicomp.on.ca>
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> > Matthew Emmerton wrote: > > > > > > Hi all, > > > > > > In the continuing saga of IPSec over PPPoE for a retail POS environment that > > > I'm maintaing, the problems seem to become more complex as time goes on. > > > > > > The network is quite simple: > > > [ LAN #1 ] - [ FreeBSD Gateway #1 ] - [ ISP ] - [ FreeBSD Gateway #2 ] - [ > > > LAN #2 ] > > > > > > Both LANs connect using PPPoE with the same ISP, and are one hop apart > > > (according to traceroute). > > > > This smells like MTU problems. Try to set the MTU on your physical LAN > > interfaces to something like 1480 or so any try again. > > That's what I thought too. I checked, and ppp is doing the TPC MSS > fixup. Even after removing the gif/ipsec stuff that I was doing > (less overhead, and converting this installation into a plain > LAN-behind-NAT setup), the problem persists. > > I tried dropping the MTU on my LAN interface to 1200 (from 1500), but that > didn't change anything. > > If my ISP installed a bunch of really buggy hardware, would that explain > why this started happening recently without any changes on my side? The answer turned out to be quite obvious. If I didn't make any changes on the FreeBSD end, and the ISP didn't make any changes on their end, then it must have been the telco (since these are DSL links.) It turned out that the telco upgraded a bunch of line equipment recently which didn't play nice with the DSL equipment that the ISP was using. After 6 hours of testing the wiring between our DSL modem and various points all the way back to the CO, the telco figured out the problem and the strangeness that we saw has gone away. Thanks for all the helpful hints and suggestions - it surely kept me from going mad. -- Matt Emmerton To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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