Getting Linux Connected, using Ethernet and TCP/IP

Special IP Addresses

Special Addresses

The following are special IP addresses reserved for use during the operation of an IP based network.

Networks / Subnets

As you cannot have a subnet number of 0 (all binary zeros) or 255 (all binary 1s), you can only have 254 subnets when using 1 octet for subnetting (ie. 2^8 -2 = 254).


As you cannot have a host number of 0 (all binary zeros) or 255 (all binary 1s), you can only have 254 hosts when using 1 octet for host addresses (ie. 2^8 - 2 = 254).

Individual Networks

Individual IP Addresses

RFC 1918 Addresses

The people at InterNIC realise that there may be organisations who want to build their own private IP based internetworks, using any old IP addressing scheme.

However, if these organisations connected to the Internet at a later date, the addresses they may have used could conflict with official Internet addresses.

To remedy this, InterNIC have allocated some Class A, B and C network addresses for use in private networks, which would not cause problems if accidently connected to the Internet. Keep in mind, these addresses will not work on the Internet either.

These network addresses are documented in RFC 1918. They are :

If you are going to create your own TCP/IP network segment using ethernet at home, and still have a machine dialing into the Internet, it is best to use one of the above Class A, B or C networks.

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LinuxSA -

Prepared by Mark Smith

Fri Feb 20 13:28:08 CST 1998