Topology:

host 1 ---------vpn-gw 1 <-----------> vpn-gw 2 --------- host 2
                     |                        |
                     |                        |
<--192.168.50.0/24-->|10.15.109.36|10.15.109.5|<--192.168.1.0/24-->

Setup:

1. Install the openswan package. Now we got 2 main files: /etc/ipsec.secrets and /etc/ipsec.conf
2. On both ends, check you have a raw RSA key using: ipsec showhostkey –left
   • If not, run «ipsec newhostkey –output /etc/ipsec.secrets» on each host missing a key.
3. Edit ipsec.conf for vpn-gw 1 & vpn-gw 2 (same exact stuff):

   • conn vpn
         authby=rsasigkey
         left=10.15.109.36
         leftsubnet=192.168.50.0/24
         leftsourceip=192.168.50.X
         leftnexthop=10.15.109.5
         leftid=@vpngw1
         leftrsasigkey=0sAQNXXXXXX
         right=10.15.109.5
         rightsubnet=192.168.1.0/24
         rightsourceip=192.168.1.X
         rightnexthop=10.15.109.36
         rightid=@vpngw2
         rightrsasigkey=0sAQNXXXXX

     • To get the proper rsasigkey values, use ipsec showhostkey. On left (vpgw1) run: ipsec showhostkey –left On right (vpngw2) run: ipsec showhostkey –right The left/rightsourceip are the local internal IP’s of the vpngw’s that are part of the subnet tunnel
4. Restart ipsec:

   • /etc/init.d/ipsec restart

5. Now you can ping from host 1 to host 2!