Subnet Masks Table

A subnet mask table can be handy when we need to calculate to the size of subnets with different prefix lengths or subnet masks. The following table lists out CIDR subnet masks along with the decimal equivalents and includes the total number of addresses as well as the total number of host addresses for each subnet mask.

Generally, while working as a network administrator or a network engineer you will mostly be working with networks of size /21 to /32. However, you may sometimes be working with larget networks (/16 to /20). You will seldom come across larger networks in practice (unless you work for a large service provider).

For this reason, it is good to be familiar with the details of /21 - /32 networks. The more familiar you are with networks of these sizes, the more comfortable you will be at your job.

IPv4 addressing and subnetting is covered in detail in this course: Course 2 - IP Addressing and Subnetting

Want to test your networking skills with hands-on configuration and troubleshooting questions? Try out the Workshops section of this website here: Workshops (Login required).

Read how to use the device simulators on this website here: Workshops - General Instructions