24-port NWay Ethernet Switch User’s Guide
78
Switch Management and Operating Concepts
Subnet Masking
A subnet mask can be applied to an IP address to identify the
network and the node parts of the address. A bitwise logical
AND operation between the IP address and the subnet mask
results in the
Network Address
(sometimes called the “
Network
Number”
).
For our example:
00001010.00101010.01001001.11010010
10.42.73.210
Class A IP address
11111111.00000000.00000000.00000000
255.0.0.0
Class A Subnet Mask
00001010.00000000.00000000.00000000
10.0.0.0
Network Address
The Default subnet masks are:
??
Class A – 11111111.00000000.00000000.00000000
255.0.0.0
??
Class B – 11111111.11111111.00000000.00000000
255.255.0.0
??
Class C – 1111111.11111111.11111111.00000000
255.255.255.0
Additional bits can be added to the default subnet mask for a
given Class to further subnet a network. This has the effect of
making the subnet mask ‘longer’. When a bitwise logical AND
operation is performed between the subnet mask and the IP
address, the result defines the network. Some restrictions apply
to the network address. Addresses of all “0”s and all “1”s are
