VPN with 3 public IPs for private internet access only

[warbux]

I do not have a lot of experience with Linux but I am really starting to like the OS as a whole. I am running the Access Server on Ubuntu 10.04 LTS 64bit XEN VPS. I have 3 public IP addresses (the below IPs are not mine)

eth0: 61.82.131.15
eth0:0: 61.82.131.13
eth0:1: 61.82.13118

I want the access server to listen on 61.82.131.13 for all connection requests (ADMIN USER AND VPN) then give out one of the above 3 public IP addresses to the user when they authenticate to the VPN. Ideally I would like it to use the same public IP address for the user each time they connect.

Currently the VPN is only used to give them private internet access when they are on the road. Eventually I will be adding more to this configuration but until then I feel like this should be a really simple task and it bothers me that I am unable to figure out how to make it do what I need it to do.