A PPTP VPN tunnel and a LAN

My knowledge of networking is kind of rudimentary so please bear
with me.

I have a box A with a NIC eth0 connected to a hub in my local
192.168.0 network. The gateway for this network is another box B with IP
address 192.168.0.1. B has tow NICs and is directly connected to a modem/
router through the second NIC, and from there to the Internet. With this
setup A (and all the other boxes in the 192.168.0 network) can access the
Internet without any problems.

What I need to do is the following:

On A I have to create PPTP-based VPN tunnel to some remote box C
with IP address CCC. I have been able to do this, in the process creating
the ppp0 interface. The question is, How can I set things up in A so that
all of A's traffic is routed through the VPN tunnel on ppp0 by default,
whereas traffic for the 192.168.0 network is routed through the eth0
interface?

I tried to establish a default route through ppp0, but it would
seem that I first have to delete the existing default gateway. But when I
do this I immediately lose the VPN tunnel. I.e. I am trapped in a vicious
circle. Any pointers on how to break it would be most welcome.

Hello,

Clark Smith a écrit :
>
> On A I have to create PPTP-based VPN tunnel to some remote box C
> with IP address CCC. I have been able to do this, in the process creating
> the ppp0 interface. The question is, How can I set things up in A so that
> all of A's traffic is routed through the VPN tunnel on ppp0 by default,
> whereas traffic for the 192.168.0 network is routed through the eth0
> interface?
>
> I tried to establish a default route through ppp0, but it would
> seem that I first have to delete the existing default gateway. But when I
> do this I immediately lose the VPN tunnel.

In order to avoid this, a host route to address CCC must be created
before changing the default route.

route add -host CCC gw 192.168.0.1
or
ip route add CCC via 192.168.0.1

What software are you using to establish the PPTP tunnel ? IIRC,
pptp-linux does this automatically.