Multi-Tech Systems MTASR1-100 - Manual (Page 13)

Chapter 1 - Introduction and Description
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The assignment of addresses is arbitrary within a company or organization, but if a company plans to connect
with the Internet anytime in the near future, a registered addresses should be obtained from the Defense Data
Network (DDN) Network Information Center (NIC), which is managed by Network Solutions in Chantilly,
Virginia. With the growing popularity of the Internet, it is recommended that all organizations obtain registered
addresses to avoid address conflicts in the future.
There are three classes of Internet addresses; Class A, B and C. Class A networks use the first byte of the IP
address for the network number and the remiaing three bytes for the host number. The first byte may have
any value from one to 127.
Class B networks use the first two bytes of the IP address for the network number and the last two bytes for
the host number. The first byte must have a value from 128 to 191.
Class C networks use the first three bytes of the IP address for the network number and the last byte for the
host number. This scheme provides for a very large number of different networks, each with up to 255
addressable devices. The first byte must have a value from 192 to 223.
The part of the IP address that refers to the network is called the network address. A network mask is the bit
pattern which yields the network address in a Boolean AND operation with the IP address. For example, in
Class C networks, network addresses take the form X.X.X.0. The network mask for Class C networks is
255.255.255.0. In all of the IP addresses on a given network, the network address will remain the same while
the host portion will be different for each host or workstation.