hello youssef
you can configure GRE tunnels between two routers and route the vpn traffic through that tunnel. simply, you configure a logical tunnel interface and give a source and destination ip address. you will then route all traffic through the tunnel interface
example:
interface Tunnel0
ip address 1.1.1.2 255.255.255.0
tunnel source loopback0
tunnel destination 192.168.3.2
!
ip route 10.1.1.0 255.255.255.0 tunnel0
other end:
int tunnel 0
ip address 1.1.1.1 255.255.255.252
tunnel source loopback0
tunnel destination x.x.x.x
you can find more examples here:
http://www.cisco.com/en/US/tech/tk827/tk369/tk287/tsd_technology_support_sub-protocol_home.html
hope this helps..
Raj
