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Private IP addresses

Any host with a direct connection to the Internet must have a globally unique IP address. However, not all hosts are connected directly to the Internet. Some are on networks that aren’t connected to the Internet. Some hosts are hidden behind firewalls, so their Internet connection is indirect.

Several blocks of IP addresses are set aside just for this purpose — for use on private networks that aren’t connected to the Internet or to use on networks hidden behind a firewall. Three such ranges of addresses exist, as summarised below. Whenever you create a private TCP/IP network, use IP addresses from one of these ranges.

Subnet Mask Address Range
255.0.0.0 10.0.0.1 – 10.255.255.254
255.255.240.0 172.16.1.1 – 172.31.255.254
255.255.0.0 192.168.0.1–192.168.255.254

Published on Sun 08 April 2007 by Alistair Pinter in Networking with tag(s): ip addresses