the 192.168.x.x (with the two x's between 0 and 255) is private address space. That is probably the adress space you should be using unless you are directly connected to your ISP, in which case the 192.186.x.x address may be right. I will say that even if you had a LAN connected by a hub (and not connected to the Internet) with the addresses 192.168.1.100, 192.186.1.100, and 192.169.1.100, they still wouldn't be able to talk to each other. You would need a router to communicate between different class B addresses, ie. ones with different numbers in the second octet.