Appendix D Ip Addresses, Network Masks, And Subnets - ZyXEL Communications Prestige 623 series User Manual

IP Addresses, Network Masks, and
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
IP Addresses
IP addresses, the Internet's 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."
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 network's class (see following section).
Class A
Class B
Class C
IP Addresses, Network Masks, and Subnets
of binary numbers, bits and bytes.
Diagram 9 IP Address structure
Field1 Field2
Network ID
Network ID
Network ID
Prestige 623 Series Dual-link ADSL Router
Appendix D
Field3 Field4
Host ID
Host ID
Host ID
Subnets
M