Date: Tue, 27 Nov 2001 11:44:45 +0100 From: Andre Oppermann <oppermann@pipeline.ch> To: Matthew Emmerton <matt@gsicomp.on.ca> Cc: freebsd-net@freebsd.org Subject: Re: Very strange network behaviour - can anyone help me analyse tcpdump output? Message-ID: <3C036E9D.21808A44@pipeline.ch> References: <004801c176e6$e57a2eb0$1200a8c0@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.
--
Andre
> The problem is that a connection from the Internet (anywhere) to either of
> the FreeBSD gateways will "hang". Usually I can login but doing an 'ls -al'
> will display a few lines of text and then nothing. This happens using a
> bunch of telnet clients (Anzio on Win2K, Win2K and Win95 native, FreeBSD)
> from various ISPs, as well as *between* the gateways, so the problem is most
> definitely related to the ISP providing us service. However, they seem to
> think that it's our problem ("none of the customers that use Windows have
> this problem -- must be that Unix thing that you're using").
>
> I have an ethereal trace of a hanging telnet session from my desktop to one
> of the gateway machines, and the corresponding tcpdump trace of the same
> session on the gateway. Since I'm not too familiar with TCP/IP at such a
> low level, I was wondering if anyone would be willing to take a look at the
> two dumps and see if there is anything strange going on.
>
> Thanks,
>
> --
> Matt Emmerton
>
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