Understanding Subnets and the Network Subnet Calculator
A subnet, or subnetwork, is a segment of an IP network (Internet Protocol suite). This suite consists of communication protocols used on the Internet and similar networks, commonly referred to as TCP/IP (Transmission Control Protocol/Internet Protocol).
The process of partitioning a network into two or more distinct networks is known as subnetting. Routers facilitate the exchange of traffic between these subnetworks, acting as physical boundaries. While IPv4 is the predominant addressing architecture, the adoption of IPv6 has been increasing since 2006.
An IP address consists of two main components: a network number (routing prefix) and a rest field (host identifier). The rest field identifies a specific host or network interface, while the routing prefix is often represented in Classless Inter-Domain Routing (CIDR) notation for both IPv4 and IPv6. CIDR provides a method for creating unique identifiers for both networks and individual devices. In IPv4, networks can also be characterized using a subnet mask, commonly shown in dot-decimal notation. All hosts within a subnetwork share the same network prefix, whereas the host identifier is unique to each local identification. Subnet masks in IPv4 distinguish between the network number and the host identifier, while in IPv6, the network prefix serves a similar role, with the prefix length indicating the number of bits in the address.
Before CIDR was introduced, the network prefixes of IPv4 could be directly derived from the IP address based on its class (A, B, or C), which varies according to the range of included IP addresses. However, with the advent of CIDR, assigning an IP address to a network interface now necessitates both an address and its corresponding network mask.
Using the Subnet Netmask Calculator
To effectively manage subnets, a netmask calculator can be invaluable. It helps to identify the correct subnet mask based on your network requirements.
Typical Subnets for IPv4
| Prefix Size | Network Mask | Usable Hosts per Subnet |
|---|---|---|
| /1 | 128.0.0.0 | 2,147,483,646 |
| /2 | 192.0.0.0 | 1,073,741,822 |
| /3 | 224.0.0.0 | 536,870,910 |
| /4 | 240.0.0.0 | 268,435,454 |
| /5 | 248.0.0.0 | 134,217,726 |
| /6 | 252.0.0.0 | 67,108,862 |
| /7 | 254.0.0.0 | 33,554,430 |
| Class A | ||
| /8 | 255.0.0.0 | 16,777,214 |
| /9 | 255.128.0.0 | 8,388,606 |
| /10 | 255.192.0.0 | 4,194,302 |
| /11 | 255.224.0.0 | 2,097,150 |
| /12 | 255.240.0.0 | 1,048,574 |
| /13 | 255.248.0.0 | 524,286 |
| /14 | 255.252.0.0 | 262,142 |
| /15 | 255.254.0.0 | 131,070 |
| Class B | ||
| /16 | 255.255.0.0 | 65,534 |
| /17 | 255.255.128.0 | 32,766 |
| /18 | 255.255.192.0 | 16,382 |
| /19 | 255.255.224.0 | 8,190 |
| /20 | 255.255.240.0 | 4,094 |
| /21 | 255.255.248.0 | 2,046 |
| /22 | 255.255.252.0 | 1,022 |
| /23 | 255.255.254.0 | 510 |
| Class C | ||
| /24 | 255.255.255.0 | 254 |
| /25 | 255.255.255.128 | 126 |
| /26 | 255.255.255.192 | 62 |
| /27 | 255.255.255.224 | 30 |
| /28 | 255.255.255.240 | 14 |
| /29 | 255.255.255.248 | 6 |
| /30 | 255.255.255.252 | 2 |
| /31 | 255.255.255.254 | 0 |
| /32 | 255.255.255.255 | 0 |
