Difference between revisions of "What is a Netmask?"
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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. | 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 | + | 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 range of the Network the rule will apply to: |
− | + | <table class="nd-othertables"> | |
− | + | <tr> | |
− | + | <th style="width: 200px">IP</th> | |
− | + | <th style="width: 200px">NETMASK</th> | |
− | + | <th style="width: 400px">DESCRIPTION</th> | |
− | + | </tr> | |
− | + | <tr> | |
− | + | <td>192.168.55.161</td> | |
− | + | <td>255.255.255.255</td> | |
− | + | <td>Only applies to 192.168.55.161</td> | |
− | + | </tr> | |
− | + | <tr> | |
− | + | <td>192.168.55.0</td> | |
− | + | <td>255.255.255.0</td> | |
− | + | <td>Applies to IPs in the 192.168.55.0 - 192.168.55.255 range</td> | |
− | + | </tr> | |
− | + | <tr> | |
− | + | <td>192.168.55.240</td> | |
− | + | <td>255.255.255.240</td> | |
− | + | <td>192.168.55.240 - 192.168.55.255</td> | |
− | + | </tr> | |
− | + | <tr> | |
− | + | <td>192.168.55.161</td> | |
− | + | <td>255.255.255.0</td> | |
− | + | <td>192.168.55.0 - 192.168.55.255</td> | |
− | + | </tr> | |
− | + | <tr> | |
+ | <td>192.168.0.0</td> | ||
+ | <td>255.255.0.0</td> | ||
+ | <td>192.168.0.0 - 192.168.255.255</td> | ||
+ | </tr> | ||
+ | </table> | ||
− | |||
− | + | Sometimes you will see that a Netmask is defined by one number, e.g., '''24'''. This number is the length of the Netmask in bits: | |
− | + | ||
− | + | <table class="nd-othertables"> | |
− | + | <tr> | |
− | + | <th style="width: 200px">NETMASK</th> | |
− | + | <th style="width: 100px">255.</th> | |
− | + | <th style="width: 100px">255.</th> | |
− | + | <th style="width: 100px">255.</th> | |
− | + | <th style="width: 100px">255</th> | |
− | + | </tr> | |
− | + | <tr> | |
− | + | <td>Netmask length</td> | |
− | + | <td>8</td> | |
− | + | <td>16</td> | |
− | + | <td>24</td> | |
+ | <td>32</td> | ||
+ | </tr> | ||
+ | </table> | ||
+ | |||
+ | |||
+ | So, for example, a Netmask that is 24-bits long is '''255.255.255.0''': | ||
+ | |||
+ | <table class="nd-othertables"> | ||
+ | <tr> | ||
+ | <th style="width: 200px">NETMASK</th> | ||
+ | <th style="width: 100px">255.</th> | ||
+ | <th style="width: 100px">255.</th> | ||
+ | <th style="width: 100px">255.</th> | ||
+ | <th style="width: 100px">0</th> | ||
+ | </tr> | ||
+ | <tr> | ||
+ | <td>Netmask length</td> | ||
+ | <td>8</td> | ||
+ | <td>16</td> | ||
+ | <td>24</td> | ||
+ | <td>-</td> | ||
+ | </tr> | ||
+ | </table> | ||
+ | |||
+ | |||
+ | A Netmask that is 16-bits long is '''255.255.0.0''': | ||
+ | |||
+ | <table class="nd-othertables"> | ||
+ | <tr> | ||
+ | <th style="width: 200px">NETMASK</th> | ||
+ | <th style="width: 100px">255.</th> | ||
+ | <th style="width: 100px">255.</th> | ||
+ | <th style="width: 100px">0.</th> | ||
+ | <th style="width: 100px">0</th> | ||
+ | </tr> | ||
+ | <tr> | ||
+ | <td>Netmask length</td> | ||
+ | <td>8</td> | ||
+ | <td>16</td> | ||
+ | <td>-</td> | ||
+ | <td>-</td> | ||
+ | </tr> | ||
+ | </table> | ||
+ | |||
+ | And so on. | ||
+ | |||
+ | [[Category:Networking]] |
Latest revision as of 07:07, 15 June 2021
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 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 that a Netmask is defined by one number, e.g., 24. This number is 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 | - |
A Netmask that is 16-bits long is 255.255.0.0:
NETMASK | 255. | 255. | 0. | 0 |
---|---|---|---|---|
Netmask length | 8 | 16 | - | - |
And so on.