Although 32 bits can accommodate over a thousand million hosts, the allocation of addresses is very inefficient. Many addresses are not easily allocatable to real hosts. A 48 bit network addressing scheme referred to as IPv6 has been defined to provide more satisfactory addressing.
The following IP addresses are allocated for local machines and will never be used by an external network
10.0.0.0 - 10.255.255.255 172.16.0.0 - 172.31.255.255 192.168.0.0 - 192.168.255.255
127.0.0.1 is always the local machine.
The broadcast address is a special address that every host on the network listens to in addition to its own unique address. This is usually the highest legal value within range, but some use the network's external address as the internal broadcast address. Either is valid, but all computers on the network must use the same broadcast addressing.
Addresses starting with 0 thru 127 are called class A addresses. Only the first numeric value (7 usable bits) is used in Internet routing. Class B addresses start with 128-191 and are routed on the basis of the first two numbers -- basically 14 bits of addressing. Class C networks start with 192-223 and use 3 numbers -- 21 usable bits. Class D addresses starting with 224-239 are reserved for multicast. The remaining 16 address groups are reserved for future use.
Rewritten Nov 2002
Return To Index Copyright 1994-2002 by Donald Kenney.