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6 ip addresses, network masks, and subnets, 1 ip addresses, 1 structure of an ip address – Asus GigaX3112 User Manual

Page 102: 6ip addresses, network masks, and subnets

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89

GigaX3112 Series Layer 3 Managed Switch

Note

6

IP addresses, network masks, and subnets

6.1 IP addresses

This section pertains only to IP addresses for IPv4 (version 4 of

the Internet Protocol). IPv6 addresses are not covered.

This section assumes basic knowledge of binary numbers, bits, and bytes.
IP addresses, the Internetʼs version of telephone numbers, are used to identify

individual nodes (computers or devices) on the Internet. Every IP address

contains four numbers, each from 0 to 255 and separated by dots (periods), e.g.

20.56.0.211. These numbers are called, from left to right, field1, field2, field3,

and field4.
This style of writing IP addresses as decimal numbers separated by dots is

called dotted decimal notation. The IP address 20.56.0.211 is read “twenty dot

fifty-six dot zero dot two-eleven.”

6.1.1 Structure of an IP address

IP addresses have a hierarchical design similar to that of telephone numbers.

For example, a 7-digit telephone number starts with a 3-digit prefix that identifies

a group of thousands of telephone lines, and ends with four digits that identify

one specific line in that group.
Similarly, IP addresses contain two kinds of information.
Network ID

Identifies a particular network within the Internet or intranet

Host ID

Identifies a particular computer or device on the network

The first part of every IP address contains the network ID, and the rest of the

address contains the host ID. The length of the network ID depends on the

networkʼs class (see following section). Table 8 shows the structure of an IP

address.

Table 8. IP address structure

Field1

Field2

Field3

Field4

Class A

Network ID Host ID

Class B

Network ID

Host ID

Class C

Network ID

Host ID

Following are examples of valid IP addresses:

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