there is a Masquerade Module for Linux which can read the TCP Control
Connection (Port 1723) for PPTP and can Forward (extended) GRE (Prot 47)
Packets. The Patch is from John Hardin and can be found on the Masquerade
Site of Indyramp:
On %M %N, Mark Plesser wrote
> Adam, PPTP is nothing more than GRE tunnel with some encryption and
> authentication on top of it. As such, those packets are IP type 47. There
> is no TCP or UDP header and, therefore, you can not proxy those packets.
> Your best bet is a packet filter like IPF.
> On Wed, 25 Feb 1998, Adam Fenn wrote:
> > Date: Wed, 25 Feb 1998 17:07:30 -0600
> > From: Adam Fenn <Adam .
> > To: 'Firewalls' <firewalls @
> > Subject: Protocol 47
> > I am messing around with PPTP on an NT RAS server. I thought I would
> > try to proxy PPTP through my bastion host. I pulled out a sniffer to
> > figure out what TCP or UDP ports PPTP used.. Turns out PPTP is a
> > transport layer protocol of it's own, protocol 47. Like TCP is 6 and
> > UDP is 17. Anyone know how I might proxy protocol 47? I am running a
> > little Linux i386 machine, with a variety of free proxy applications.
> > Thanks!
> > Adam
> Mark Plesser
> Morgan Stanley & Co. (212) 762-1990
> 750 7th Avenue, 9th Floor, New York, NY 10019
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