Quick and Dirty Subnet Mask CheatSheet

This is just quick and dirty cheatsheet for subnet masks. It compares the relationship of host bits, prefix length, subnet mask, and usable IP addresses per subnet.

Host Bits	Prefix Length	Subnet Mask	Usable IP Addresses
1	/31	255.255.255.254	2¹-2 = 0*
2	/30	255.255.255.252	2²-2 = 2
3	/29	255.255.255.248	2³-2 = 6
4	/28	255.255.255.240	2⁴-2 = 14
5	/27	255.255.255.224	2⁵-2 = 30
6	/26	255.255.255.192	2⁶-2 = 62
7	/25	255.255.255.128	2⁷-2 = 126
8	/24	255.255.255.0	2⁸-2 = 254
9	/23	255.255.254.0	2⁹-2 = 510
10	/22	255.255.252.0	2¹⁰-2 = 1022

What is Subnetting?

Subnetting is a networking concept that allows you to divide a larger network into smaller, more manageable sub-networks, known as subnets. This is done by borrowing bits from the host portion of an IP address and using them to create additional network addresses.

Here's a more detailed explanation of subnetting:

IP Address Structure

An IP address is composed of two main parts: the network portion and the host portion.
The network portion identifies the network, while the host portion identifies individual devices within that network.

Purpose of Subnetting

Subnetting helps to improve network efficiency, security, and scalability.
It allows you to create multiple smaller networks (subnets) within a larger network, each with its own network address and range of available host addresses.
This can help to reduce network congestion, improve network performance, and make it easier to implement access control and routing policies.

The Subnetting Process

Subnetting involves borrowing bits from the host portion of the IP address and using them to create additional network addresses.
The number of bits borrowed determines the number of subnets and the number of hosts per subnet.
For example, if you have a Class C network (e.g., 192.168.1.0/24) and you borrow 2 bits from the host portion, you can create 4 subnets (2^2 = 4) with 62 hosts per subnet (2^6 - 2).

Benefits of Subnetting

Improved network performance: Subnetting can help reduce network congestion and improve overall network performance by containing network traffic within the appropriate subnets.
Enhanced security: Subnetting can help to isolate and secure different parts of the network, making it more difficult for unauthorized access or network attacks.
Efficient use of IP addresses: Subnetting allows you to make better use of available IP addresses by dividing a larger network into smaller, more manageable subnets.
Easier network management: Subnetting simplifies network administration and makes it easier to implement routing policies, access control lists, and other network management tasks.

Subnetting is a fundamental concept in network design and is widely used in both small and large-scale networks to improve efficiency, security, and scalability.

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Posted: 2024-07-23
By: dwirch
Viewed: 89 times

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