I'm still pretty new to Linux, and have never set up a tunnel before.

I have a Linux box running Centos 6.5, with 2 NICs which will be used to tunnel a /16 of IP addresses from a client to be used on our network. eth1 is configured with a static IP. Since I don't have access to our router, I was told setting up this Linux box would take the place of the router.

What are the proper steps and commands to set up a tunnel for these IPs to be routed, and usable on my network?

Thanks for your help.