Help with subnetting

Greetings again everyone!

Hope everyone is doing fantastic! I wanted to reach out with a few questions. My final class started a few weeks ago for my degree (Networking). The class is Inter-networking, essentially it deals with Cisco related stuff. So far, we’ve dealt with inter vlan routing, routing protocols, switch and router configuration, learning frames and packets. It’s a hybrid class, so we do virtual podcasts and have one in person lab a week. Since this is my first in person college class (Covid), I had a rough start getting in the swing of things. My issue currently is that subnetting is making things so difficult. I cannot seem to make sense of it, I’ve had a few friends attempt to explain it but it just hasn’t clicked.

I honestly am not sure where to start, the way these classes are setup it’s proving quite difficult to get a solution that helps me. I have no problems remembering the proper commands, just when subnetting needs to be figured into the equation. Can someone give me some help? I don’t know where to start, I am getting easily confused. I need to learn this sooner than later, I want to be up to par so that I can excel and be successful going forward.

Sorry that was a lot to take in, hopefully someone can relate. Thanks so much for allowing me to vent / find a solution here.

I don’t have any beginner tutorials on the topic, but there are plenty of them on YouTube. Lots of people explain things in different ways so try a few until you find the one that causes it to suddenly make sense.


Hey Tom!

Hope all is well, I’ve noticed every time I researched or asked someone, they each had different methods. Kind of sucks with school because if deadlines. I usually find myself relearning topics once I get a break where I can actually sit down and try to make sense. Unfortunately, this seems like a topic that needs to be learned and understood quite early. Fortunately, I dislike not knowing so the motivation to learn is there.

As always, I appreciate your response. I’m glad you do what you do, it’s people like you that help the people like me. I am grateful to be able to have a place to go and ask questions. So thank you very much.

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Hey, drinky -

The roots of subnetting are in binary math. Once you understand binary, the rest (including why Cisco ACL masks look backward) comes much more into focus. As Tom has already mentioned, the 'Tube is chock full of resources, and here’s a couple that I have found informative / entertaining / useful:

David Bombal’s CCNA courses - It took me a while to get into David’s style, he used to come across as rather dry to me (my issue, not his). His content is spot on, though, and he explains things very thoroughly. Since I brought up binary math, here’s a direct link to the (~12 minute) episode where he explains it.

Chris Greer, whom I found while watching David Bombal videos, knows wireshark (and, by extension, how networks network) like nobody I’ve ever seen.

This list would not be complete without Network Chuck - for a highly caffeinated view of pretty much all things server / network related. Not as finely focused on the networking concepts that you need, but entertaining and informative. Link is to a short series specifically about subnetting and addressing.

While you’re on the intertubes, download either GNS3 or EVE-NG. Get your personal lab set up, it’ll help greatly in making practical sense out of the abstract concepts you’ll be learning.

Good luck!

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Hey man!!

Thank you so much for the resources. I will get right on to these links. Going to put a lot of time and effort into learning subnetting. I will let you know how it goes! Thanks again.


Like you, I struggled with subnetting when I first looked at it. The video linked below isn’t what I used, but it’s pretty similar. After all my studying I went into the exam and wrote out a chart like she does in this video. Once you get the hang of using something like this it makes subnetting fairly easy.


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I will definitely check that link out. My professor actually made a website for subnetting, I seem to have got an understanding of his practice questions. Here is the link the students use to practice. I can do all of those problems, but I’m still confused about what part of subnetting that is specifically.

Once you get the hang of subnetting, you can download a self-contained HTML file for putting in information such as network address, start address, end address, and broadcast address based on the IP address given. If you get it wrong, the information below will give you some hints.

It’s in the “IPv4 Subnetting Practice App” section.