Subnet Mask Cheat Sheets
A subnet mask cheat sheet simplifies the process of subnetting and ensures efficient use of IP address spaces. Whether working with IPv4 or IPv6, these tools enhance productivity and accuracy in network design and troubleshooting.
A subnet mask cheat sheet provides a quick reference for understanding subnet masks, addressing ranges, and CIDR notations. This guide explains key concepts related to subnetting and includes both IPv4 and IPv6 cheat sheets to simplify these tasks.
For additional technical details, consult RFC 1878, the authoritative guide to IPv4 subnetting.
What is a subnet?
A subnet, or subnetwork, is a segment of a larger network. It allows network administrators to organize and manage IP addresses efficiently by dividing a network into smaller parts. Subnetting improves routing efficiency, enhances security, and conserves IP addresses.
Related resource: [Video] What are subnet routers?
What is a subnet mask?
The subnet mask is a 32-bit number that resembles an IP address, distinguishing the network portion of an IP address from its host portion. By "masking" bits, it reveals which part of the IP address identifies the network and which part identifies the device.
What is a subnet mask cheat sheet?
A subnet mask cheat sheet is a reference tool used by network administrators to simplify subnetting tasks. It lists subnet masks, Classless Inter-Domain Routing (CIDR) notations, and their corresponding address ranges, available hosts, and wildcard masks. With this cheat sheet, IT professionals can easily determine the number of usable addresses and the division of networks.
What are IPv4 addresses?
IPv4 (Internet Protocol version 4) addresses are 32-bit numerical labels assigned to devices on a network. They use the dot-decimal format (e.g., 192.168.1.1) and support approximately 4.3 billion unique addresses. Subnetting is essential in IPv4 networks due to the limited address space.
What are IPv6 addresses?
IPv6 (Internet Protocol version 6) addresses are the successor to IPv4. They are 128-bit addresses written in hexadecimal format (e.g., 2001:0db8::1) and offer a vastly expanded address pool. IPv6 supports advanced features like improved routing and built-in security, making it suitable for modern networking.
Subnet Mask Cheat Sheet
See also RFC 1878.
| CIDR | Addresses | Hosts | Netmask | Amount of a Class C |
|---|---|---|---|---|
| /30 | 4 | 2 | 255.255.255.252 | 1/64 |
| /29 | 8 | 6 | 255.255.255.248 | 1/32 |
| /28 | 16 | 14 | 255.255.255.240 | 1/16 |
| /27 | 32 | 30 | 255.255.255.224 | 1/8 |
| /26 | 64 | 62 | 255.255.255.192 | 1/4 |
| /25 | 128 | 126 | 255.255.255.128 | 1/2 |
| /24 | 256 | 254 | 255.255.255.0 | 1 |
| /23 | 512 | 510 | 255.255.254.0 | 2 |
| /22 | 1024 | 1022 | 255.255.252.0 | 4 |
| /21 | 2048 | 2046 | 255.255.248.0 | 8 |
| /20 | 4096 | 4094 | 255.255.240.0 | 16 |
| /19 | 8192 | 8190 | 255.255.224.0 | 32 |
| /18 | 16384 | 16382 | 255.255.192.0 | 64 |
| /17 | 32768 | 32766 | 255.255.128.0 | 128 |
| /16 | 65536 | 65534 | 255.255.0.0 | 256 |
IPv4 subnet mask cheat sheet
The following table provides a quick reference for IPv4 subnet masks, their CIDR notation, the number of usable host addresses, and wildcard masks.
| CIDR | Subnet Mask | # of Addresses | Usable Hosts | Wildcard Mask |
|---|---|---|---|---|
| /32 | 255.255.255.255 | 1 | 0 | 0.0.0.0 |
| /31 | 255.255.255.254 | 2 | 0 | 0.0.0.1 |
| /30 | 255.255.255.252 | 4 | 2 | 0.0.0.3 |
| /29 | 255.255.255.248 | 8 | 6 | 0.0.0.7 |
| /28 | 255.255.255.240 | 16 | 14 | 0.0.0.15 |
| /27 | 255.255.255.224 | 32 | 30 | 0.0.0.31 |
| /26 | 255.255.255.192 | 64 | 62 | 0.0.0.63 |
| /25 | 255.255.255.128 | 128 | 126 | 0.0.0.127 |
| /24 | 255.255.255.0 | 256 | 254 | 0.0.0.255 |
| /23 | 255.255.254.0 | 512 | 510 | 0.0.1.255 |
| /22 | 255.255.252.0 | 1,024 | 1,022 | 0.0.3.255 |
| /21 | 255.255.248.0 | 2,048 | 2,046 | 0.0.7.255 |
| /20 | 255.255.240.0 | 4,096 | 4,094 | 0.0.15.255 |
IPv6 subnet cheat sheet
IPv6 networks offer a vastly larger address space. The following table provides a reference for IPv6 prefix lengths and address counts:
| Prefix Length | # of Subnets | Addresses per Subnet |
|---|---|---|
| /48 | 1 | 1.2 septillion |
| /56 | 256 | 4.7 quadrillion |
| /64 | 65,536 | 18 quintillion |
| /127 | 340 undecillion | 1 |
IPv6 cheat sheets are designed for large-scale networks. For detailed planning, refer to official resources like the IPv6 Subnetting Guide.
Related Subnet Resources
[Blog] Subnet routers: How do they work?
[Docs] Subnet routers
[Guide] Configure a subnet router
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