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IP Networking Basics Netmask
X320R User’s Guide 71
3. N
ETMASK
The netmask allows you to identify the network and host portions of an address
without knowing the address class. The netmask is a 32-bit number, expressed in
dot-notation, that is logically ANDed with the IP address to yield the network
address.
The IP address classes have corresponding netmasks:
• Class A - 255.0.0.0
• Class B - 255.255.0.0
• Class C - 255.255.255.0
For example, the IP address 192.168.1.15 is a Class C address broken down as fol-
lows:
IP Address
11000000.10101000.00000001.00001111 (192.168.1.15)
Netmask
11111111.11111111.11111111.00000000 (255.255.255.0)
-------- -------- -------- --------
ANDed
11000000.10101000.00000001.00000000 (192.168.1.0)
Where 192.168.1.0 is the IP address identifying the network.
4. S
UBNET
Subnet addressing allows a network to be split into smaller subnetworks. For
example, if a Class C network address is assigned to a small company, it may be
unlikely for that company to use all 254 host addresses. Instead, the 254 host net-
work may be divided into several smaller subnets. A company can then assign