answer:IP address ranges are allocated to ISP’s by companies like IANA who decide who gets what. So your ISP will be allocated a certain address range, say 163.6.0.1 – 163.7.2.1 (as a generic example). Your ISP will then have something like a large number of DHCP servers which your computer will ‘communicate’ with, you use the login details, your computer ‘talks’ to the ISP’s computers and then they assign an IP Address to you. If you’re ISP uses dynamic IP address’ it will just allocate you an IP address within it’s range that is currently free. If it’s fixed the ISP servers will just give you the same IP address everytime (see Dynamic and static IP addresses). As for local networks it works on the same concept but they’re limited to the addresses allocated for private networks. For example, my router acts as a small DHCP server and so the computers on my home network will get the next free IP address available when the computers start up, or I can set which computers can have which IP by using a computer’s MAC address which is a unique ID to each ethernet enabled device. I hope that’s clear/informative, if not don’t hesitate to ask for more information. I’m not an expert and I’ve no idea how the actual inner workings of an ISP works because I’ve never worked for one. But I know somewhere the ISP will be allocated an IP address range which will then allocate you one of these IP addresses for your usage. Edit: oh, and domain names and IP addresses are a new subject altogether, which I do understand the basics of to :)