For a post that is a little more advanced, try this one: Create a Router With Front Firewall Using Vyatta on VMware Workstation.
Otherwise… read on.
A few weeks ago, I installed Vyatta Open Source as a router internal to my network to see how it handled traffic between multiple subnets. To put it plainly, it worked like a champ! I put the router in place, assigned IP addresses to the NICs (network interface cards), and let the system do its thing. It now connects traffic between my physical network, my production virtual network, and my virtual lab running on ESX 3.5. I can easily manage most firewalls and routers that have a GUI but Vyatta presented a new challenge to me. In the case of this system, for some tasks it’s a lot easier to use the command line interface (CLI).
So without further ado, here’s the basics of Vyatta’s firewall.