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Re: IP masquerading and ADSL



Eran,
use mru 1542 and mtu 1542 in your pptp command  to reduce the packet size
received from the peer.
This is updated in the new HOWTO
Dani

On Sun, 4 Feb 2001, Eran Tromer wrote:

> Hello,
> 
> I tried reducing the MTU on the client box, and it doesn't help. I can't
> see why it should -- the problem occurs when the *remote* host is
> sending a large packet *into* the LAN.
> 
> Looking at captured network traffic both between the masquerading box
> and the ADL modem and between the masquerading box and the client box, I
> see no packet larger than 500 bytes. This means that the large packets
> are eaten by the ADSL modem, or earlier somewhere out there.
> 
>   Eran
> 
> 
> Dani Arbel wrote:
> > 
> > reduce the maxmtu of the win boxes to 1452 and they will work fine.
> > Dani
> > 
> > On Sat, 3 Feb 2001, Eran Tromer wrote:
> > 
> > > Howdy list,
> > >
> > > Thanks to mulix, my Linux ADSL connection is up and running. Next, I set
> > > up IP masquerading, and encountered the following odd problem.
> > >
> > > When conneting from some host on the LAN, every time the remote host
> > > tries to send "a lot of data at once" (a large TCP packet, perhaps?),
> > > the masqueraded TCP connection is lost. So, for instance, when
> > > telnetting to a POP server I can download short e-mails -- any number of
> > > them, in fact -- but if I try to RETR a long e-mail the connection is
> > > immediately broken (I don't even get the header). The same happens on
> > > other ports (e.g, HTTP only retrieves short pages, telnet breaks on long
> > > 'ls' outputs).
> > >
> > > >From the masquerading box (the one talking to the ADSL modem), all works
> > > fine.
> > >
> > > Notably, the same happens with Windows2000 masquerading using ADSL,
> > > while ISDN masquerading worked fine on the same Windows2000 box. I would
> > > have suspected a fault in the modem (Orckit ATUR3) or ISP (Internet
> > > Gold), but they're not supposed to be able to distinguish masqueraded
> > > sessions, at least not nonmaliciously.
> > >
> > > On the Linux box which runs kernel 2.4.1, I set up masquerading using
> > > # insmod ipchains
> > > # ipfwadm-wrapper -F -a m -S 192.168.0.0/16 -D 0.0.0.0/0
> > > (yes, compatibility layer upon compatibility layer, but may Murphy curse
> > > me if I relearn those arcane command line options yet again!)
> > >
> > > I would have tried a 2.2 kernel, but since the same problem occurs with
> > > Windows2000 this probably won't change anything.
> > >
> > > Any ideas? Did anyone else encounter this?
> > >
> > >   Regards,
> > >     Eran Tromer
> > >
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