Editing Subnet (section)

===Subnet host count===
The number of subnets available and the number of possible hosts in a network may be readily calculated. For instance, the {{IPaddr|192.168.5.0|24}} network may be subdivided into the following four {{IPaddr||26}} subnets. The highlighted two address bits become part of the network number in this process.
{| class="wikitable"
! Network
! Network (binary)
! Broadcast address
|-
| 192.168.5.0/26
| <code>11000000.10101000.00000101.'''00'''000000</code>
| 192.168.5.63
|-
| 192.168.5.64/26
| <code>11000000.10101000.00000101.'''01'''000000</code>
| 192.168.5.127
|-
| 192.168.5.128/26
| <code>11000000.10101000.00000101.'''10'''000000</code>
| 192.168.5.191
|-
| 192.168.5.192/26
| <code>11000000.10101000.00000101.'''11'''000000</code>
| 192.168.5.255
|}

The remaining bits after the subnet bits are used for addressing hosts within the subnet. In the above example, the subnet mask consists of 26 bits, making it 255.255.255.192, leaving 6 bits for the host identifier. This allows for 62 host combinations (2<sup>6</sup>−2).

In general, the number of available hosts on a subnet is 2<sup>''h''</sup>−2, where ''h'' is the number of bits used for the host portion of the address. The number of available subnets is 2<sup>''n''</sup>, where ''n'' is the number of bits used for the network portion of the address.

There is an exception to this rule for 31-bit subnet masks,<ref name="rfc3021">{{Cite IETF|rfc=3021|title=Using 31-Bit Prefixes on IPv4 Point-to-Point Links|author1=A. Retana|author2=R. White|author3=V. Fuller|author4=D. McPherson|date=December 2000}}</ref> which means the host identifier is only one bit long for two permissible addresses. In such networks, usually [[Point-to-point (telecommunications)|point-to-point links]], only two hosts (the endpoints) may be connected and a specification of network and broadcast addresses is not necessary.

{| class="wikitable sortable"
|+ Subnet masks and IP addresses
|-
! Mask !! IP addresses !! Hosts !! Netmask
|-
| {{IPaddr||31}} || 2 || 2 || {{IPaddr|255.255.255.254}}
|-
| {{IPaddr||30}} || 4 || 2 || {{IPaddr|255.255.255.252}}
|-
|{{IPaddr||29}}
|8
|6
|{{IPaddr|255.255.255.248}}
|-
|{{IPaddr||28}}
|16
|14
|{{IPaddr|255.255.255.240}}
|-
|{{IPaddr||27}}
|32
|30
|{{IPaddr|255.255.255.224}}
|-
|{{IPaddr||26}}
|64
|62
|{{IPaddr|255.255.255.192}}
|-
|{{IPaddr||25}}
|128
|126
|{{IPaddr|255.255.255.128}}
|-
|{{IPaddr||24}}
|256
|254
|{{IPaddr|255.255.255.0}}
|-
|{{IPaddr||23}}
|512
|510
|{{IPaddr|255.255.254.0}}
|-
|{{IPaddr||22}}
|1024
|1022
|{{IPaddr|255.255.252.0}}
|-
|{{IPaddr||21}}
|2048
|2046
|{{IPaddr|255.255.248.0}}
|-
|{{IPaddr||20}}
|4096
|4094
|{{IPaddr|255.255.240.0}}
|-
|{{IPaddr||19}}
|8192
|8190
|{{IPaddr|255.255.224.0}}
|-
|{{IPaddr||18}}
|16384
|16382
|{{IPaddr|255.255.192.0}}
|-
|{{IPaddr||17}}
|32768
|32766
|{{IPaddr|255.255.128.0}}
|-
|{{IPaddr||16}}
|65536
|65534
|{{IPaddr|255.255.0.0}}
|}