If you are an information technology or cybersecurity professional, and you are planning to study for and take a networking certification such as CompTIA’s Network+ or Cisco’s CCENT, CCNA, or CCNP, then you will need to know and understand IP addressing, subnetting, and supernetting inside and out. When I was studying for the CCNA years ago, I put together a set of subnetting spreadsheets, and eventually shared it on my two principal websites. You can find them at on the Reference Desk page. The Ref Desk page is very frequently visited, according to Google Analytics.
I was introduced to an outstanding article that covered this issue better than anything I have ever read on the subject, including most of the official certification text books. I was asked to include a link to this article, and since I use this page all the time when teaching a networking class, I was happy to make the addition.
Steven Cooper is the author responsible for The Ultimate Guide to Subnetting – plus 10 Best Subnet Calculators and Cheat Sheet. The article covers the following topics:
- 1 Why subnet?
- 2 What is subnetting?
- 3 Broadcast address and network address
- 4 The subnet mask
- 5 Subnetting shortcuts
- 6 Variable-length subnet masking
- 7 The Best Subnet Calculators
- 8 Master IP Subnetting
- 9 Subnetting Cheat Sheet
I know many of my students have struggled with the concepts of IP addressing, subnetting, and classless interdomain routing (CIDR). Even if you have been working in IT or networking for a while, you still might appreciate the depth and clarity that Steven brings to a subject that has bedeviled many of us at some point in our careers. Give it a read.Share