Information Technology Reference
In-Depth Information
Class A Addresses
Class A addresses range from 0 (00000000) to 127 (01111111) in the first octet. Network
numbers assigned to companies range from 1.0.0.0 to 126.0.0.0, with networks 0 and 127 being
reserved. For example, 127.0.0.1 is reserved for the local host. Also, network 10.0.0.0 is
reserved for private addresses.
By default, for Class A addresses, the first octet is the network number and the three remaining
octets are the host number. In the format N.H.H.H, N is the network part and H the host part.
With 24 bits available, there are 2 24 - 2 = 16,777,214 IP addresses for host assignment. Two are
subtracted for the network number (all 0s) and broadcast address (all 1s). A network with this
many hosts attempting to broadcast on the network surely cannot work. This problem is
resolved with subnetting, which is discussed in this section.
Class B Addresses
Class B addresses range from 128 (10000000) to 191 (10111111) in the first octet. Network
numbers assigned to companies or other organizations range from 128.0.0.0 to 191.255.0.0.
There are 16 networks reserved for private use; these are shown later in this section.
By default, for Class B addresses, the first two octets are the network number and the remaining
two octets are for the host number. The format is N.N.H.H. With 16 bits available, there are
2 16 - 2 = 65534 IP addresses for host assignment. As with Class A addresses, a segment with
over 65,000 hosts broadcasting cannot work; this is resolved with subnetting.
Class C Addresses
Class C addresses range from 192 (11000000) to 223 (11011111) in the first octet. Network
numbers assigned to companies range from 192.0.0.0 to 223.255.255.0. The format is N.N.N.H.
With 8 bits available, there are 2 8 - 2 = 254 IP addresses for host assignment. H=0 is the
network number; H=255 is the broadcast address.
Class D Addresses
Class D addresses range from 224 (11100000) to 239 (11101111) in the first octet. Network
numbers are assigned to multicast groups that range from 224.0.0.1 to 239.255.255.255. These
addresses do not have a host or network part. Some multicast addresses are already assigned;
for example, routers that run EIGRP use 224.0.0.10.
Class E Addresses
Class E addresses range from 240 (11110000) to 254 (11111110) in the first octet. These
addresses are reserved for experimental networks. Network 255 is reserved for the broadcast
address, such as 255.255.255.255.
Search WWH ::




Custom Search