ATL Telecom AM30 - Manual (Page 157)

ATL Telecom User Guide
AM30
1
5
7
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.
fNetwork ID
Identifies a particular network within the Internet or
intranet
fHost 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 3 shows the structure of an IP address.
Table 3. 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)