Filter
Top Products
12
IP Addresses Section 1-7
1-7 IP Addresses
Ethernet networks use IP addresses for communications. IP addresses (Inter-
net addresses) identify both the Ethernet network and the node (host com-
puter, Ethernet Unit, etc.) on the Ethernet network. IP addresses must be set
and controlled so that they are not duplicated.
1-7-1 IP Address Configuration
IP addresses are made up of 32 bits of binary data divided into four 8-bit fields
called octets. These four octets provide the network number (net ID) and host
number (host ID). The network number identifies the network and the host
number identifies the node (or host) on the network.
The network numbers in an IP addresses are divided into three classes, A, B,
and C, so that the address system can be selected according to the scale of
the network. (Classes D and E are not used.) The configuration of the IP
address for each of these classes is shown in the following diagram.
The number of networks in each class and the number of nodes possible on
the network differ according to the class.
IP addresses are represented by the decimal equivalent of each of the four
octets in the 32-bit address, each separated by a period. For example, the
binary address 10000010 00111010 00010001 00100000 would be rep-
resented as 130.58.17.32.
Note The same network number must be set for every node on the same Ethernet
network.
1-7-2 Allocating IP Addresses
IP (Internet Protocol) is a standard communications protocol used throughout
the world and is designed to enable communications between any Ethernet
Class A
Bit 31
0 Network number (7 bits) Host number (24 bits)
23
00
Class B
Bit 31
1 Network number (14 bits) Host number (16 bits)
15 00
0
Class C
Bit 31
1 Network number (21 bits) Host number (8 bits)
700
1 0
Class D
Bit 31
Class E
Bit 31
Multicast address
Test address
(Cannot be used.)
1 1 1 0
00
1 1 1 1
00
(Cannot be used.)
Class Number of networks Number of hosts
Class A Small
2
24
– 2 max. (16,777,214 max.)
Class B Medium
2
16
– 2 max. (65.534 max.)
Class C Large
2
8
– 2 max. (254 max.)