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Created 08 Apr 2002
Modified 20 May 2007

Article 9

What is an IP Address?

An IP Address ( Internet Protocol Address) is computer's unique address on the internet. Each packet of data on the internet contains a source and destination IP address, so information can be routed accordingly. Any network device such as routers, computers, servers, printers, fax machines and some telephones can have their own address.

Note: Some IP addresses are internal to your local network, and not routable to the internet. The following 3 blocks of the IP address space have been reserved by the Internet Assigned Numbers Authority (IANA) for private Intranets:

10.0.0.0 - 10.255.255.255 (10/8 prefix)
172.16.0.0 - 172.31.255.255 (172.16/12 prefix)
192.168.0.0 - 192.168.255.255 (192.168/16 prefix)

If your PC is assigned an IP address in one of the above ranges, it is most probably behind a firewall, running NAT or SOCKS. In this case, the IP packets sent to the internet are addressed from the firewall, and not from your PC.

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