I have 4506 core and 3550 edge switches. I have a cable modem in a building on the other end of campus. I want to basically run that single connection my the cable modem to a PC that is located in another building. I know that the cable modem comes with some external IP. Do I need to setup a VLAN with the external IP info or can I just get a cheap linksys router, assign it a IP, and then match my vpn with the router?