What is a Subnet Mask???

Video Notes:

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Ready to learn one of the most important parts of Subnetting? Of course you are! In this video, Chuck dives into one of the most important topics related to Subnetting, the Subnet mask!

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0:00 ⏩ Intro

1:08 ⏩ Let’s flex our binary conversion skills!

5:22 ⏩ Time to check our work!

7:10 ⏩ The numbers are whispering to us?

8:44 ⏩ This is the best way to find the total number of hosts in a network!

11:10 ⏩ Converting our binary mask back to decimal

12:18 ⏩ outro

The subnet mask. This is how we create the networks of the world. This is where the magic of subnetting actually happens. That’s why every IP address, even your IP address has a subnet mask. And it tells us all the secrets about the network. Well, most of them, some of ’em you’ll see here is my toilet and his IP address. Oh, whoops. Forgot to flush. And here is his subnet mask. Now you may recall that Mr. Subnet mask job is to tell us how big our network is, how many IP addresses are there and, and more, and you may even remember our little hack. Remember here, if we see a 2 55 in the subnet mask, we know that the corresponding OCTE or the corresponding number in our IP address is frozen. Just it’s done. It can’t move. It won’t change. But the big question is why, like why does 2 55 mean that number stays the same? 

What’s actually happening here. What’s the subnet mask doing? Why is it 2 55 in this episode, we’re gonna pop the hood on that. We’re gonna see what the heck is happening. <laugh> why is it doing and what it does. And why is the subnet mask so important? Now in the previous episode, I gave you super powers. You are now able to decode matrix computer code <laugh> I think, uh, yeah, you can look at N IP address and convert it into binary, the language of computers, and you can convert it back and actually real quick, pause the video and see if you can convert our current IP address, the IP address a might boil it into binary. Keeping in mind. This will be a lot easier if you use the help of our handy Danny chart and no for all too. So pause the video and go, Hey, time for a coffee break. 

And this coffee break in the entire video is sponsored by big fix. Oh, that’s good. Now, while you’re shipping that coffee, let’s talk about something a bit scary, cyber breaches. You, you know, they happen. They happen all the time. Solar winds, Equifax, Google Okta, and then like blog four J that was crazy not to mention ransomware, basically just lots of bad things happening to companies, making them lose money, making them lose your data on the dark web. And ultimately they lose respect. Now you’re probably thinking, why does this keep happening? Why haven’t they stopped this? You know what, actually, I’m kinda surprised this doesn’t happen more often because here’s the reality managing it infrastructure for large companies or even just small companies is crazy hard. Actually. It’s kind of almost impossible. Hundreds, sometimes thousands, tens of thousands of endpoints that you have to make sure stay safe and adding to the complexity. 

They’re not all the same, right? They’re not all in one place like the office they’re gonna be at someone’s house, you know, working from home coffee shops and the cloud. And also they’re kind of all different, right? Like they’re running different operating systems like iOS windows, Linux, and it could be anything from a laptop to a phone, to a kiosk. And I know you probably had the situation, cuz it’s happened to me. You may have this old server running this ancient version of Linux sitting underneath someone’s desk in like Kansas or something. How are you going to find and update that when you don’t even know it’s there? And the reality is it only takes one of these devices to leave you vulnerable to a massive hack. So are you scared yet? One more sip of coffee. I told you it wasn’t gonna be an easy coffee break. 

So how do companies small to large handle large it infrastructures are things that are everywhere all at once because some companies do handle it. Well, these are the companies you don’t hear about because they’re not getting hacked. They will use solutions like HCLs big fix, which is totally awesome because here’s what it does. It will automate the discovery, the management and remediation of all endpoints. And when I see all, I mean stink in all, whether it’s on-prem and your data center at someone’s desk, in the office, at their home office and then Antarctica or under a desk in Kansas collecting dust. And it doesn’t matter what OS they had. It could be Lenox, Mac, iOS, whatever they can manage it. And you can do all of this from a centralized console. It teams can deploy patches and updates to their entire it landscape. Again, no matter where it’s at, it could be sitting in someone’s pocket. 

It could be, you know, the phone or something or the old grandpa, sir. Now I’ve been there. I know the pain, if you’re in it operations or it security. How nice would it be to just be able to manage everything with one tool and also like just have a handle on things, know where everything is. Cuz I know as an it admin and really just anyone in it. You’re thinking you have that sneaking suspicion. Is there something I don’t know about? Am I missing something? Did I update that server? A new vulnerability comes out and it’s like the most disgusting one in the world. It’s gonna bring down your company. And you’re like, I don’t know if my stuff is updated. I don’t even know how to find all the stuff. That’s where tools like big fix come in. It’ll give you better collaboration between teams cuz you know it ops security. 

Everyone is gonna know through one console where things are what’s going on. Is this server patch? What OS is this running? So you’ll be able to cut down an operational cost and you can enforce what’s called continuous compliance, which again, when audit time comes around. So I know like when I say audit, you get chills and I’ve been through a few of they’re terrible, but with big fix, you’ve got your arms around everything. They generate these amazing reports automatically four of these compliance standards saying, Hey yeah, everything’s up to date or Hey we know the system isn’t patched. We’re gonna patch it real quick with one button. And a lot of these fixes are automatic. They use intelligent automation. They even have these things called fixates, which sound like Chiclets, which provide all these benefits and make it really easy just to deploy fixes to things. 

And because it’ll automate a lot of the tasks you might like be doing manually right now. Like what are you doing today? You’re probably just gonna be patching servers right? All day. Do you have to pull up a report? I mean, it’s just a pain, right? But big fix will free up that time. So you can focus on the fun stuff. The fun projects, things that challenge you and remind you why you got into it in the first place. So free up those evenings, free up those weekends, lower that anxiety and stress check out big fix. I got a link below big fix.com. You can actually sign up for some free training to see, Hey, what can this do for me? That can do a whole lot. And Hey, thanks for having some coffee with me. Let’s get back to the video. UN pause, coffee break, and done. 

This is my toilet’s IP address and binary, a computer code and matrix code. And if you’re wondering, how did he do that? Go back and watch the previous episode. I show you how it’s remarkably simple and kind of fun. Actually know it’s very fun. Just go do it. Now, what we did not do in the last video is convert our subnet mask into binary, which is something we totally can do, should do and will do right now. And this one’s kind of remarkably easy. So for example, if I bring my first number down here, my first OCTE 255 and I wanna see if the first bit is gonna be on or off one or zero can 128 be subtractive from 2 55. Uh, 

Yes. A hundred percent. Yes it can. That first bit is on. So 2 55 minus 1 28 gives us 1 27. Bring that over here. Can we take 64 away from 1 27? Yes we can. That bit is on 1 27 minus 64 gives us 63. Can we take 32 away from 63? Yes we can. That bit is on. So 63 minus 32 gives us 31. Now I’m gonna give you a little spoiler alert. We’ll be able to turn every bit on that’s the secret. We will go down every single digit until finally that 2 55 is zero. Because if you add all these numbers together here in our chart, you’re gonna get 255 go and do it real quick. Let’s do it with our calculator. 1 28 plus 64 32 16 8 4 2 1 255. Knowing that 2 55 means every bit and that Octa will be on. Go ahead and finish out the mask. It’s kind of easy, right? 

This is our subnet mask. Converted into binary, all ones all the way across in the first three. Octets the last one. Also easy because zero and binary is still zero. All the bits are off because you can’t take any of these numbers away from zero. Now, here, here is where it’s all gonna come together and make sense. And, and, and why we’re converting stuff into binary anyway, like what’s the point? Here’s the point? Because if you listen closely, these wines and zeros in our subnet mask, they’re speaking to us, they’re telling us something. They’re whispering things about our network. Dark mysteries. If you can’t hear, I’ll go. I’ll go ahead and tell you, sorry. That was stupid. <laugh> but stick with me. Take a sip of coffee. Get excited. When you’re looking at the subnet mask, the ones tell us they whisper to us, which part of the IP address are the network bits. 

So looking here, we can tell that dude, we got lots of ones, all ones all the way down in our first three octets, which means every one of these bits appear in our subnet mask all the way down through all three octets are the network bits. So network bits, AKA the part of the IPAs that won’t change and tells us which network we’re on. And then it’s also whispering something else to us here. Listen, closely, listen, the zeros they tell us which parts of the IP address are host bits. So looking at our mask, we can see that the entire fourth Octa is all zeros. So we know in the IP address every bit and the fourth Octa will be a host of it. Meaning each of these bits can be used to create an IP address and that network and be assigned to that host. 

Now I know this is weird <laugh> but here’s one example of how this is cool. So the zeros tell us which bits are host bits, which also tells us how many possible hosts there are in the network. All we gotta do is count the number of bits. So looking here at our subnet mask, how many bits are zeros? I mean, they’re all in the last OCTE, they’re eight, eight zeros. And I know what you’re probably thinking, well, Chuck, I counted eight zeros, but I know, I know looking at this network, this network can have more than eight IP addresses and you’re right. We’re not done yet because there is a formula with this to see how many hosts can be in any network. Here it is. This is so powerful. Just put this in your pocket, man. It’s gonna be two to the power of zeros. How many zeros there are? So for example, our example here, <laugh>, let’s grab a calculator. If I take two and I do my little power, two 

Of something, the carrot, right? Two to the power of how many zeros eight that gives us 256, which is absolutely correct. In this network, we can have 256 IP addresses. Now, of course we can’t use all of them. We have to subtract two to account for the subnet ID or the subnet address and the broadcast address the first and last IP address in the network, which gives us a total of the 254 usable IP addresses. So the official formula would be two to the power of number zeros minus two, because every network will have those two IP addresses reserved. So with this unlocks is something crazy, powerful, because we know if we count the zeros, it gives us 254 usable IP addresses. But if we’re like, Hey, I need more than that in my network, I need, I need like 500 IP addresses in that, in my network. 

How do I get more? The simple answer is we need more zeros. We need more host bits to have more hosts and to do that, we’re gonna borrow or we’re gonna steal from the network. We’re kind of like peeking behind the curtain of the next video, or we’re really gonna break it down. I just wanna give you a peek. I can’t tell you too much, but if I come over to this subnet mask here, I’m gonna take away one of the network’s bits. I wanna take this last one and convert it to a zero you’re on the host team. Welcome. So now with the extra zero, how many hosts can this network have? Let’s try it out. Let’s use our formula two to the power of number of zeros. Well, now we have not eight zeros, but nine zeros. So with our handy dandy calculator, two to the power of nine will give us 512 addresses, which minus two gives us 510 usable addresses. 

So right here, I want you to understand what just happened. We converted our mask and our IP address into binary. Well, for this moment, that was just like a, a, a thing you had to learn to do and exercise. Now it’s coming together. Cuz what we just did is we went from having 254 available host and we said, no, not good enough for me. I want more IP addresses in my network. Another one, another one I want more. I want 500. So we stole a bit from the network side, giving us more host that that’s subnetting. We, you just subnetting because all really subnetting is, is changing the subnet mask to suit our needs. So here’s a challenge for you real quick. We changed our subnet mask, which means the value in decimal is gonna be different. It will no longer be 2 5 5, 2 5 5 2 5 5 0. Cuz we changed something. 

We changed the third OCTE so real quick, let’s convert it back to decimal back to the regular version of it and see what it looks like now, right off the bat. We know that the first two octets will be the exact same they’re all once. But the third one, it won’t be 2 55 anymore. It’s gonna be different. We know the first let’s see seven, seven bits here are gonna be on bam. Bam, bam, bam, bam, bam, bam. Just like that. And hour shift that you’re gonna do is add these numbers together and a result will be, and you may have been able to do this in your head. The result will be 2 54. That’s our new subnet mask with 512 possible IP addresses or 510 usable IP addresses. Now what just happened here with nothing short of magic. And I’m leading a lot of questions unanswered like, Hey dude, what’s our range of IP addresses. 

Like how what’s the network look like from like what IP address to what IP address. I’m not gonna cover that right now. We’re gonna cover that in the next episode where we’re gonna break down subnetting even more and do a lot more of it. That’s that’s what I’m trying to say. But one more thing before we end this episode, I want you to notice in our subnet mask, the numbers are contiguous, which is a weird word. I always love saying cuz it feels like continuous with adding a G contiguous, meaning that the ones will always be in a row like you won’t suddenly have 1, 1, 1 0. No, no that will never happen. The numbers are contiguous. It’ll always be a row of ones. It’ll always be a row of zeros. So in this episode we uncovered a few of the deep dark secrets of the subnet mask. 

He tells us how big our network is. He tells us how many IP addresses we have. But in this episode we actually dove deeper into how that works and what’s actually happening. And in the next episode, we’re gonna dive even deeper because these ones and zeros, they’re not done whispering to us. They have some more secrets that we haven’t uncovered yet. So I’ll see you then. And by the way, if you want some extra practice converting your subnet masks into decimal and back to binary and vice versa, check out network check academy, link below. I’ve got a ton of extra practice for you. Oh and also, Hey, have you hacked the YouTube algorithm today? Let’s make sure you do hit that leg button notification about comment. Subscribe. You gotta hack YouTube today. Ethically of course. Yeah. That’s all I got. I’ll catch you guys next time.

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