Release IP address on Snow Leopard

Depends on your internet. DHCP is going to pull the first available IP address from whatever DHCP server it'c connected to. If you're connected to a Local Wireless or Wired Router, and you release that IP address, as soon as you try to get another one You might very well get the same one if it's released back in to the IP pool of the server. Now if you're plugged directly into a cable modem or something like that, Internet providers usually assign IP addresses based on the MAC of the device connected, so without MAC spoofing, there would be no way to pull a different IP.