The Joys of Subnetting

I have been studying for my CompTIA Network+ certification exam. This is the one of the early career trifecta (A+, Network+, & Security+) that I had been hoping to avoid. I was hoping that I might be able to find a cybersecurity track job without needing the Network+, so I could forego that exam entirely. Now the exam itself may not be a necessary for getting into cybersecurity, however understanding networking in general is absolutely necessary. And not only that, my experience of trying to get into IT for the last five years, with a year since getting both my A+ and Security+, Network+ seems to be the most sought after of the three. So I begrudgingly got my exam voucher and began studying.

Much to my surprise, I am finding the content to be deeply engaging. I am loving the deep dive into the inner workings of IP addressing and how packets of data move from one host to another. Much like the bulk of the Western world, I have also taken much of the internet for granted. I am enthralled how bits turn into frames, frames into packets, packets into segments, segments into sessions, how segments pass through layer 6 to set encoding, encryption, and compression; and finally how that is presented to the end-user on the output side. Why these exams are made to be taken in order makes a lot of sense. Of course, like the contrarian I can be at times, I took them third-first-second. But I kept looking at IPv4 and IPv6 addresses, MAC addresses, and the like and was intimidated.

However, I that intimidation has since washed away after confidently learning how to manually subnet. I read numerous articles, watched a myriad of videos, only to come away scratching my head each time. I was convinced that I could never learn to do it. And that was when someone suggested (Practical Networking)[]. Specifically, I watched his video series, (Subnetting Mastery)[], and it all came together. It stems from the concept of a subnetting “cheat sheet.” This cheat sheet framework was not new to me, as I had seen (Professor Messer)[] do it, as well as (Jason Dion)[]. Both of these great instructors give cheat sheet examples, but Practical Networking taught me how to make the cheat sheet. And in the understanding of how to make the cheat sheet, I began to understand how subnetting works from a mathematical and theoretical standpoint. And the best thing about all of it, unlike many aspects of tech certification exams, is that I don’t need to memorize anything. I just have to remember which variable I am using and where, and with some practice, which was greatly enjoyable thanks to the achievement rush I was getting, I can now easily figure out the subnet of a given IP, when coupled with a CIDR suffix, the subnet ID, the broadcast IP, the first and last usable IP on the subnet, the beginning of the next, and the number of addresses available on that subnet.

Over the next few blog posts, I will layout how to make a subnetting cheat sheet, and I will show some examples of how to use it, specifically between the different network subnet masks. I realized that this is kind of going the way of the DoDo Bird these days, between the wider implementation of IPv6, and that we have apps for this sort of thing now. But I have found this process to be greatly useful in understanding how networks and subnets are made and how bits move across the network. And this sort of intimate hands on experience is worth gold in the modern age.