[pptp-server] PPTP VPN up, but how to forward all traffic through the VPN?

[Scott M. Stone]

On Tue, 7 Mar 2000, Antti A Luostarinen wrote:

> Ok, I have successfully created the PPTP VPN (guys, the GRE didn't go
> through, there was a little fumble in the router access-lists :)) but
> now my problem is the following..
> 
> 
> What I want:
> 
> I'm on a cable-modem. I want to tunnel all traffic through the VPN to
> the pptpd (I mean ALL traffic that happens after I have made the
> connection) and onwards to the Internet. (Why: where the pptpd resides,
> I have much better routes to the World than which my cable-modem
> operator has.)
> 
> How do I do this? If I mark "use default gateway" on the TCP/IP
> properties of the connection icon, it seems to try to use my PPTP VPN
> but I get nothing through.. In the FAQ/HOWTO's ppl are suggesting to
> turn it off..
> 
> If I turn it off, my routes are whatever my cable-modem ISP routes are
> regardless if the VPN connection was made or not.

Because nothing on the outside has any idea how to route traffic BACK to
you.  Make sure that your pptp client is being assigned an IP address
that's on the same local subnet as the ethernet interface on the pptpd
server, and that you're using proxyarp on the server.  Otherwise the
routing will never work unless your ISP's distribution/core routers have a
route added to point back to your private subnet, which Probably Isn't
Going To Happen. :)

--------------------------
Scott M. Stone, CCNA <sstone at taos.com>
UNIX Systems and Network Engineer
Taos - The SysAdmin Company