I'm trying to configure my firewall to block all connections to the Internet, while still allowing access to other computers on my LAN and local IP address assignment by my router's DHCP service. Which IP ranges do I need to allow?
Generally, all LAN IP's are 192.168.(0 or 1).0-299 If you can set your firewall to only allow connections with 192.168.* (star being wild card) All network activity should be allowed, but no Internet activity.
Best thing to do would be assign static IP addresses, or assign your DHCP server to set unlimited lease time on the addresses. Then, block the computers you want in your server's settings. (I guess it's a router in this case?)
By the way: IPv4 Addresses only go up to 255 (255.255.255.255)