Difference between revisions of "What is a Netmask?"

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(Created page with "A '''Netmask''' is a 32-bit "mask" used to divide an IP address into subnets and specify the network's available hosts. In a netmask, two bits are always automatically assigne...")
 
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{| class="wikitable"
 
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! style="width: 200px; background: black; color: white;" | Netmask
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! style="width: 200px; background: black; color: white;" | Netmask
! style="width: 200px; background: black; color: white;" | 255.
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! style="width: 200px; background: black; color: white;" | 255.
! style="width: 200px; background: black; color: white;" | 255.
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! style="width: 200px; background: black; color: white;" | 255.
! style="width: 200px; background: black; color: white;" | 255.
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! style="width: 200px; background: black; color: white;" | 255.
! style="width: 200px; background: black; color: white;" | 255
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! style="width: 200px; background: black; color: white;" | 255
 
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|-
! style="text-align: left; vertical-align: top;" | Netmask length
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! style="text-align: left; vertical-align: top;"   | Netmask length
| style="text-align: left; vertical-align: top;" | 8
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| style="text-align: center; vertical-align: top;" | 8
| style="text-align: left; vertical-align: top;" | 16
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| style="text-align: center; vertical-align: top;" | 16
| style="text-align: left; vertical-align: top;" | 24
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| style="text-align: center; vertical-align: top;" | 24
| style="text-align: left; vertical-align: top;" | 32
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| style="text-align: center; vertical-align: top;" | 32
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|-
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|}
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So, for example, a Netmask that is 24-bits long is '''255.255.255.0''':
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{| class="wikitable"
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|+
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! style="width: 200px; background: black; color: white;" | Netmask
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! style="width: 200px; background: black; color: white;" | 255.
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! style="width: 200px; background: black; color: white;" | 255.
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! style="width: 200px; background: black; color: white;" | 255.
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! style="width: 200px; background: black; color: white;" | 0
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|-
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! style="text-align: left; vertical-align: top;"  | Netmask length
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| style="text-align: center; vertical-align: top;" | 8
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| style="text-align: center; vertical-align: top;" | 16
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| style="text-align: center; vertical-align: top;" | 24
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| style="text-align: center; vertical-align: top;" | -
 
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Revision as of 09:41, 16 January 2018

Main Page > FAQ > Networking > What is a Netmask?

A Netmask is a 32-bit "mask" used to divide an IP address into subnets and specify the network's available hosts. In a netmask, two bits are always automatically assigned. For example, in 255.255.225.0, "0" is the assigned network address. In 255.255.255.255, "255" is the assigned broadcast address. The 0 and 255 are always assigned and cannot be used.

Netmask defines how "large" a network is or if you're configuring a rule that requires an IP address and a Netmask, the Netmask will signify to what portion or range of the Network the rule will apply to:

IP Netmask Description
192.168.55.161 255.255.255.255 Only applies to 192.168.55.161
192.168.55.0 255.255.255.0 Applies to IPs in the 192.168.55.0 - 192.168.55.255 range
192.168.55.240 255.255.255.240 192.168.55.240 - 192.168.55.255
192.168.55.161 255.255.255.0 192.168.55.0 - 192.168.55.255
192.168.0.0 255.255.0.0 192.168.0.0 - 192.168.255.255

Sometimes you will see a Netmask that is defined by one number, e.g., 24. This number is a the length of the Netmask in bits:

Netmask 255. 255. 255. 255
Netmask length 8 16 24 32

So, for example, a Netmask that is 24-bits long is 255.255.255.0:


Netmask 255. 255. 255. 0
Netmask length 8 16 24 -