Re: Why running PPTP client behind double NAT fails ?

PPTP's data channel uses GRE (IP Protocol 47), and GRE does not work with
PAT (by default), since GRE does not have any ports associcated with it.

Most vendors do special fixups/inspections/ALGs to fix this issue. Most
probably one of your devices does not support GRE/PPTP fixup or has not been
properly configured to do so.

So most probably the Double NAT is not the reason for PPTP failure, but some
device is not supporting the GRE fixup properly.

Regards

Farrukh

On Wed, Mar 17, 2010 at 10:14 AM, jeremy co <jeremy.cool14_at_gmail.com> wrote:

> Basically, platforms was not Cisco
>
> It was a lame setup of a DSL modem and an AccessPoint. modem was
> "speedStream" and AP was Linksys.
>
> PPTP connections on client laptops was not working. Everything was fine
> after change the whole setup to a single NAT.
>
> Any comment of why it didn't work on double nat scenario highly
> appreciated.
>
>
>
> Jeremy
>
> On Wed, Mar 17, 2010 at 1:57 PM, Ryan West <rwest_at_zyedge.com> wrote:
>
> > Fixup / inspect not enabled on the second NAT?
> >
> > -ryan
> >
> > > -----Original Message-----
> > > From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf
> Of
> > jeremy
> > > co
> > > Sent: Tuesday, March 16, 2010 10:43 PM
> > > To: Cisco certification
> > > Subject: Why running PPTP client behind double NAT fails ?
> > >
> > > Hi ,
> > >
> > >
> > >
> > > I ran Windows Vista PPTP client behind double NAT and it fails fails ,
> > it's
> > > working behind the single NAT though.
> > >
> > >
> > >
> > > As I couldn't find any valid reason , somebody might be able to shed
> some
> > > lights on this.
> > >
> > >
> > > Cheers,
> > >
> > > Jeremy
> > >
> > >
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> > >
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>
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Received on Wed Mar 17 2010 - 10:28:45 ART