What is a Netmask?: Difference between revisions
No edit summary |
No edit summary |
||
(12 intermediate revisions by 5 users not shown) | |||
Line 1: | Line 1: | ||
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''': | 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''': | 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. | And so on. | ||
[[Category:Networking]] |
Latest revision as of 06:07, 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.