LinkMAX HSA300 ADSL Ethernet Router User’s Guide
Appendix
A
. IP Addresses, Network Masks, and Subnets
124
A
IP Addresses, Network Masks, and Subnets
IP Addresses
Note
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. For details on this subject, see Appendix 0.
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). Table 2
shows the structure of an IP address.
Table 2. 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
Here are some examples of valid IP addresses:
Class A: 10.30.6.125 (network = 10, host = 30.6.125)
Class B: 129.88.16.49 (network = 129.88, host = 16.49)
Class C: 192.60.201.11 (network = 192.60.201, host = 11)
