Ip Addresses; Ip Address Configuration; Allocating Ip Addresses - Omron CJ1W-ETN21 - 04-2009 Operation Manual

IP Addresses

5-1

IP Addresses

5-1-1

IP Address Configuration

Note
5-1-2

Allocating IP Addresses

94
Ethernet networks use IP addresses for communications. IP addresses iden-
tify both the Ethernet network and the node (host computer, Ethernet Unit,
etc.). IP addresses must be set and controlled so that they are not duplicated.
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 address 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.
Bit 31
Class A 0
Network number (7 bits)
Bit 31
Class B 1 0 Network number (14 bits)
Bit 31
Class C 1 1 0 Network number (21 bits)
Bit 31
Class D 1 1 0
Bit 31
Class E 1 1 1
The number of networks in each class and the number of nodes possible on
the network differ according to the class.
Class
Class A
Class B
Class C
The 32 bits of an IP address are divided into four sections of eight bits each,
and expressed as a punctuated number. IP addresses are represented by the
decimal equivalent of each of the four octets in the 32-bit address, each sepa-
rated by a period. For example, the binary address 10000010 00111010
00010001 00100000 would be represented as 130.58.17.32.
The same network number must be set for every node on the same Ethernet
network.
IP (Internet Protocol) is a standard communications protocol used throughout
the world, and is designed to enable communications between any Ethernet
nodes regardless of the networks on which they exist. To achieve this, net-
work numbers are allocated by the Network Solutions, InterNIC Registration
Services, to ensure that all Ethernet networks have unique numbers regard-
less of where they exist. The local system administrator is left the responsibil-
ity of allocating unique host numbers locally. You therefore should obtain a
network number from the InterNIC Registration Services to ensure unique-
ness and allow for future network expansions if required.
23
Host number (24 bits)
15
Host number (16 bits)
7
Host number (8 bits)
Multicast address
Identification address
Number of networks
Small
Medium
Large
Section 5-1
0
0
0
0
(Cannot be used.)
0
(Cannot be used.)
Number of hosts
24
−2 max. (16,777,214 max.)
2
16
−2 max. (65,534 max.)
2
8 −2 max. (254 max.)
2