OK - I tried Guy's advice and came up with 1372 + 28 = 1400 which is exactly
what was already suggested and didn't solve my problem. I had already set the
Win98 MTU to 1400 in the registry according to the instructions in the
ADSL-Bezeq HOWTO. I'm obviously doing something wrong. But I still have two
questions:
1 - Is there any way to check if the MTU is actually set as it should be? I
tried **playing** with ethereal a bit, but to be honest, I have no idea what
I'm looking for and there is so much info that I'm lost ;-)
2 - As I originally asked, what could cause this problem to suddenly appear?
To make myself clearer - I've been using ADSL since the original Bezeq trial
period so for years Win98 machines on my network have had no problems until
recently (about 3 weeks ago, I think). I know of no changes (but of course
there must be something) on the Linux box. And I'm sure there were no changes
in Win98 because:
a - my wife and kids would't know how or what to change
b - it makes no sense that a change would be made on all 3 Win98s
c - all Win98s have up-to-date anti-virus so I rule out a virus
On Wednesday 19 November 2003 20:48, Guy Teverovsky wrote:
> Yes. It looks OK. This should adjust the client's MTU to the size
> determined by PathMTU Discovery initiated from the router.
>
> Try the following to eliminate a problem with MTU:
> From your Win98 box run:
> ping -f -l xxxx java.sun.com
> where xxxx is TCP's payload size.
> Start from 1472 and go down till you get a reply instead of "Packet
> needs to be fragmented but DF set".
> Record the largest value which results in reply, add 28 to that number
> (TCP headers size) and set the NIC's MTU to that value.
>
> For example, if I get reply after "ping -f -l 1464", I would set the MTU
> to 1492.
>
> Guy
>
> On Tue, 2003-11-18 at 05:44, Shlomo Solomon wrote:
> > I do, but I admit to not knowing what that means - is this what you
> > meant?
> >
> > [EMAIL PROTECTED] solomon]# iptables -L|grep clamp
> > TCPMSS tcp -- anywhere anywhere tcp
> > flags:SYN,RST/SYN TCPMSS clamp to PMTU
> >
> > On Tuesday 18 November 2003 04:36, Guy Teverovsky wrote:
> > > Do you have --clamp-mss-to-pmtu in your iptables script ?
> > > Something like:
> > > $IPTABLES -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS \
> > > --clamp-mss-to-pmtu
> > >
> > > Guy
> > >
> > > On Mon, 2003-11-17 at 22:45, Shlomo Solomon wrote:
> > > > Hi,
> > > >
> > > > My network consists of my Mandrake 9.1 box and 3 Win98 machines. All
> > > > 4 machines and my Alcatel ADSL modem are connected to a hub and I run
> > > > iptables with masquerading to allow the Win98 machines access to the
> > > > internet. Until recently, all machines could reach any URL. But
> > > > recently, the Win98 machines cannot reach certain URLs. I suspected a
> > > > DNS problem so I tried equivalent IP addresses but that didn't help.
> > > > The strange thing is that **most** URLs are still reachable and I
> > > > haven't noticed any common factor in the unreachable ones. Also, the
> > > > URLs that can't be reached on the 3 Win98 machines can be reached by
> > > > Mozilla on the Mandrake machine. Of course, I also cheched if the
> > > > URLs could be reached from Windows machines not connected to my
> > > > network. So the problem does seem to be here.
> > > >
> > > > Any ideas where to look? I'm enclosing two examples of unreachable
> > > > URLs:
> > > >
> > > > www.maariv.co.il
> > > > www.simil.vze.com
> > > >
> > > > TIA
>
> --
--
Shlomo Solomon
http://come.to/shlomo.solomon
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