Subnet Mask Cheat Sheet

Introduction

Networking is a crucial aspect of modern technology, and understanding subnet masks is essential for anyone involved in network design or administration. Smarthost is pleased to provide this Subnet Mask Cheat Sheet which provides a clear and concise reference for subnetting

Whether you’re a seasoned professional or just starting, this cheat sheet will enhance your networking toolkit.

Further details on Subnetting can be found here: RFC 1878.

What is a Subnet Mask?

Understanding the Basics A subnet mask is a 32-bit number that divides the IP address into network and host parts. It’s used in IP networking to create subnetworks, allowing for efficient use of IP addresses and improved network security and performance.

Practical Use of Subnet Masks

Subnet masks enable the division of an IP address space into multiple network segments, managing and optimizing network traffic. This is crucial in large networks where managing traffic and resources efficiently is key.

How to Utilise the Cheat Sheet

This Subnet Mask Cheat Sheet lists various subnet masks along with the corresponding number of addresses, hosts, and the size of each subnet. It’s an easy-to-reference guide for quickly determining the subnetting information you need.

Sub Class C Blocks

/25 — 2 Subnets — 126 Hosts / Subnet

/26 — 4 Subnets — 62 Hosts / Subnet

/27 — 8 Subnets — 30 Hosts / Subnet

/28 — 16 Subnets — 14 Hosts/Subnet

/29 — 32 Subnets — 6 Hosts/Subnet

/30 — 64 Subnets — 2 Hosts/Subnet

In-depth Guide

Detailed Explanations of Subnetting Options

Dive into Subnetting

Subnetting involves dividing a network into smaller parts, called subnets. Each subnet is represented by a subnet mask. The cheat sheet provides a range of subnet masks from /30 to /16, detailing the number of possible addresses, the number of usable hosts, and how much of a Class C network each represents.

Example of a Subnet Mask

Consider a /24 subnet mask, which is represented as 255.255.255.0. This allows for 256 addresses with 254 usable hosts. It’s equivalent to one Class C network. This is commonly used in small to medium-sized networks.

Understanding Larger Subnets

Larger subnets like /16 (255.255.0.0) allow for more hosts, suitable for larger networks. This subnet mask provides 65,536 addresses, with 65,534 hosts usable, representing 256 Class C networks.

Smaller Subnets for Efficiency

Conversely, a smaller subnet like /30 (255.255.255.252) allows for 4 addresses with 2 usable hosts, ideal for small networks or point-to-point links.

Summary

Understanding subnet masks and their application is key to efficient network management. We encourage you to use the Subnet Mask Cheat Sheet as a reference in your networking tasks. For further assistance or information, our support team is always ready to help.