Address Classes - D-Link DES-3250TG User Manual

DES-3250TG Layer 2 Fast Ethernet Switch User's Guide

Address Classes

Address classes refer to the range of numbers in the subnet
mask. Grouping the subnet masks into classes makes the task
of dividing a network into subnets a bit easier.
There are five address classes. The first four bits in the IP
address determine which class the IP address falls in.
•
Class A addresses begin with 0xxx, or 1 to 126 decimal.
•
Class B addresses begin with 10xx, or 128 to 191 decimal.
•
Class C addresses begin with 110x, or 192 to 223 decimal.
•
Class D addresses begin with 1110, or 224 to 239
decimal.
•
Class E addresses begin with 1111, or 240 to 254
decimal.
Addresses beginning with 01111111, or 127 decimal, are
reserved. They are used for internal testing on a local machine
(called loopback). The address 127.0.0.1 can always be pinged
from a local node because it forms a loopback and points back
to the same node.
Class D addresses are reserved for multicasting.
Class E Addresses are reserved for future use. They are not
used for node addresses.
The part of the IP address that belongs to the network is the
part that is 'hidden' by the '1's in the subnet mask. This can be
seen below:
•
Class A
•
Class B
•
Class C
For example, the IP address 10.42.73.210 is a Class A address,
so the Network part of the address (called the Network Address)
NETWORK.node.node.node
NETWORK.NETWORK.node.node
NETWORK.NETWORK.NETWORK.node
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