[notice]For this example I use the following IP scheme 192.168.0.12|–O–42.42.42.42—–[INTERNET]——12.12.12.12–O–|10.42.42.42[/notice]
I was approached a few weeks back to assist in creating a VPN Tunnel between two end points. Of course in my naivety I readily assumed it was between to Cisco devices but that turned out not to be the case. The tunnel was to be between a Linux box (in this case Ubuntu on a hosted VPS provider) and an unknown endpoint. This tunnel was going to be host to host as opposed to LAN to LAN. After some quick discovery work, getting access to the Linux box, and seeing the required proposal from the other side I started diving into the unknown of Openswan. Luckily, after doing som research for the configuration and verification things started shaping up and much to my approval, a lot of what you would look for in Cisco verification was the same on the Linux box. The configuration goes as such.
Naturally the first step is to install Openswan. As per usual use your distributions software management to install this. The first thing I configured was the ipsec configuration file. On the Ubuntu box this resided in “/etc/ipsec.conf”. The configuration was as follows.