Why We're Out of IP Addresses: Mismanagement and Classful Addressing
This video explains why the internet's 4.3 billion IPv4 addresses are nearly exhausted, focusing on the poor planning of the internet's inventors and the classful addressing system they created. It sets the stage for understanding subnetting and IPv6 as solutions.
The Core Problem: Mismanagement of IP Addresses
The internet's creators failed to anticipate two key factors: the massive growth of the internet and the explosion of devices needing IP addresses (from computers to smart appliances). This led to inefficient allocation and waste.
Classful Addressing: How IPs Were Organized
The IPv4 address space was divided into five classes (A, B, C, D, and E), each with a fixed default subnet mask that determined network size. To fully understand these classes, it's essential to master subnetting basics.
Class A Networks (1.0.0.0 – 126.0.0.0)
- Default Subnet Mask: 255.0.0.0
- Hosts per Network: 16,777,214 (over 16 million)
- Total Networks: 126
- Purpose: Designed for large organizations like governments and big corporations (e.g., GE, IBM, AT&T).
- Problem: Far too many addresses per network, leading to massive waste.
Class B Networks (128.0.0.0 – 191.255.0.0)
- Default Subnet Mask: 255.255.0.0
- Hosts per Network: 65,534
- Total Networks: 16,382
- Purpose: For medium-sized organizations.
- Problem: Still too many hosts per network for most companies.
Class C Networks (192.0.0.0 – 223.255.255.0)
- Default Subnet Mask: 255.255.255.0
- Hosts per Network: 254
- Total Networks: 2,097,150
- Purpose: For small networks, including typical home networks.
- Key Takeaway: This was the most efficient class, but was not used for all networks.
Class D (224.0.0.0 – 239.255.255.255) and Class E (240.0.0.0 – 255.255.255.255)
- Class D: Reserved for multicast traffic.
- Class E: Reserved for experimental use.
- Impact: These entire ranges are unusable for standard host addressing, wasting millions of IP addresses.
The Huge Waste: The Loopback Address (127.0.0.0)
- Missing Range: The address range 127.0.0.0 – 127.255.255.255 (a full Class A network) is reserved for loopback testing.
- Function: Allows a device to send a packet to itself to verify TCP/IP is working (e.g., ping 127.0.0.1). Understanding this requires a solid grasp of IP, TCP, and UDP fundamentals.
- Critique: Only one IP address (127.0.0.1) was needed for testing, but over 16 million addresses were locked away for this purpose.
The Takeaway: Why It Matters
- Inefficiency: The classful system created massive networks (Class A and B) that were far larger than needed, leading to millions of unused public IP addresses.
- Waste: Entire classes (D, E) and the loopback range are off-limits for general use.
- The Band-Aid: Modern networks use classless subnetting (CIDR) to chop up large allocated blocks into smaller, usable chunks, delaying the crisis.
- Next Steps: The future is IPv6, but subnetting helps stretch the remaining IPv4 space.
Key Takeaway for Learners
This video is part of a CCNA subnetting series. Memorizing the class ranges and default subnet masks is critical for certification exams and real-world networking. The mismanagement shown here explains why engineers had to invent tools like CIDR and private IP addressing (not covered in this video). For a deeper dive into how routers handle these addresses, explore CCNA routing fundamentals.
Now, I'm not sure if you knew this, but there are roughly 4.3 billion possible IP addresses and we're out like we don't have anymore, which is a huge problem.
Because as you saw in our last video, if a device wants to communicate on the internet or with other devices, it needs an IP address. So in this video,
I wanna talk about how is that even possible, right? Because the people who invented the internet were pretty stink and smart, but you see around the time they invented it,
which the Internet's birthday is officially January 1st, 1983, it seemed like the 4.3 billion supply of IP addresses was inexhaustible. Right? I mean, it sounds like it might be,
but they didn't understand two big things that honestly, they probably couldn't see coming. The internet became kind of a big deal, obviously. Right. And second, they did not anticipate all the,
that we would assign IP addresses too. I mean, think about it. They're like, oh yeah, maybe a few computers here and there. No, your watch your oven, your microwave, your toilet now,
because they did not understand these two things would happen. They did some pretty stink and dumb things. They mismanaged the heck out of our IP address space. So in this video,
we're gonna explore that. What did they do? And later we'll talk about how we fixed it, kind of with the bandaid. So by the end of this video,
not only will you understand why the inventors of the internet were very terrible planners, you'll also understand a lot about IP addresses. We're building on the foundation that we set in the first video,
and this video will prepare you to become a master chief ninja subnetting skill master chief ninja, because it is part of my series. You suck at subnetting. So make sure you catch all the episodes anyways, real quick.
Can I show you something right, right back here, this guy right here, that little raspberry pie is running an entire business phone system. It's called three CX. It's amazing. And it's sponsor of today's video.
Now you may remember me doing a video on setting up three CX on a raspberry pie right here. I also did it in the cloud. Why not only was it an insanely fun project,
but three CX is an incredible phone system. And this is coming from a guy who worked with Cisco phone systems. They're probably wondering Chuck,
why would you put a phone system in your house? And I would say, well, first, why not? It's just cool. And second three CX makes it super easy because a lot of the features that you
would be nickled and dime for that cost so much are actually free. One of the biggest things is you have unlimited users on your system, which trust me is awesome. And also as a small business owner myself,
I use three CX as my phone system for my business. I have a toll free number in the cloud. I get free video conferencing and my business is fully remote.
And three CX is built for that. Now I also made another video. You can check it out right here, where I play with her live chat. I deployed it to my website. So right from my assistant soft phone,
she could take calls, take live video chats, right from my website, which is kind of crazy. So if you're a nerd, for sure, try the on premise install for three CX or any other computer you have in your
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you can have this on premise or put that sucker up in the cloud. Now, check this out. You get three C X free for a year. And not just the software. If you don't wanna host this yourself,
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And just as a, a nerd and a hobbyist. So check it out, link below. So let's talk about how the inventors of the internet mismanaged and mishandled are 4.3 billion IP addresses. And if you wanna get nerdy,
it's actually two to the 32nd power, which is actually 4 billion, 294 million, 967,296, IP addresses. But you 4.3 billion close enough. So here's what they did.
And it comes down to how they organized the IP addresses. They put them into what are called classes. B C, D E. Yeah, that's it a C D E. And there are two problems I have with this first,
there are large groups of IP addresses that we can't even use. I know like why you'll see. And second, they set it up to where they gave away too many IP addresses. Because again,
they didn't expect the internet to take off and so many devices to have IP addresses. So they gave big companies just, Hey, he, why don't you take 16 million IP addresses? Just take 'em. Well, we don't care.
We have so many right now. We'll never run out idiots. Anyways, here. Here's what they did. So you need recall from the first video that N IP address is four numbers
separated by three dots. And each of these numbers can be anything between zero and 255, which using big brain math will give you a total of, well, right up here,
see the top 4.3 billion IP addresses, but man, they screw it up. So here's the classes. Here's how they organize these IP addresses. So here's the chart. Here's how we group 'em.
I'm not gonna list every one of 'em off. That would be super boring. So just look you can read, but seriously, if you're studying for an exam where you have to know subnetting in the classes,
then you might wanna make flashcards out of this and memorize it. Now at first glance, there's nothing wrong with this. Actually, there is one big glaring problem with it, between a and B.
See if you can notice it. We'll talk about that here in a second, but the problem doesn't come in until this very weird thing they did here. It comes, you ready? Hmm. The subnet mask classes,
a B and C each have their own default subnet mask, which if you recall, from our last video, it determines basically how big the network is or which numbers an I IP address
stay the same and which ones change. For example, let's take the first network we have here in class a, we have the 1 0 0 0 network. This is how it would look here. Let's draw it out.
There's the IP. And here is the subnet mask. If you remember the hack I talked about, when you see a 2 55 in the subnet mask, the corresponding or matched up OCTE, which is the first one here,
and the first one here will stay the same. So one will always be in the IP address. And when you see a zero anyone's game, it can be any number between zero and 255.
Now that is a pretty stink and big network, because if we're just keeping the first Octa at the same, the one, but everything else can be different. Do you know how many addresses that is?
That is, I gotta look it up. Oh my goodness. 16 million, 777,214 IP addresses and one network, which is ends sane. Especially when you contrast that with your home network,
which we talked about in the first video might look like this. There's the IP address and here's the subnet mask. And with 3, 2 50 fives, we're locking in those first three numbers leaving the last one,
the last OCTE to be anything which with this is a humble 256 addresses. So 2 56 versus 16 million. Why? Well,
the idea was that government entities or big companies might need a lot of IP addresses. And since they had plenty 4.3 billion, let's just give 'em a whole bunch. And that's what they class a was for.
And you might recognize some of the companies that have these class, a IP address networks like general electric, GE they own 3, 0, 0, 0, IBM has nine at and T has 12 Xerox, 13 HP, 15.
Each of these companies owns over 16 million IP addresses. So looking back at our class, a range class, a networks are very host heavy because they give you so many stinking hosts over
16 million. And thanks to their default subnet mask. There are only 126 total class a networks. Now you're probably thinking, Chuck, are there actually networks like that big,
like 1 0, 0, 0 with 2 55, 0, 0, 0 is a subnet mask. That's a lot of IP addresses in one network. And the answer is no, they don't really make 'em that big. Yes.
The governing body who hands out IP addresses the Santa clause of IP addresses or the head Oprah, we call them IANA or IANA, the internet assigned numbers, authority they will assign or allocate all those IP addresses that entire
network to a company will pick on IBM for a second with their nine network. What they will do is take this huge network full of IP addresses and cut it up into smaller slices.
So they might have the network 9.40 with a subnet mask of 2 55, 2 5, 5 0. And you're probably thinking, whoa, they can do that. Yeah. So while a class,
a network has the default subnet mask of 2 55, 0 0 0 0, that's the minimum they have to have. They can cut it up very small and say in this network, the,
the one and the four will always be an IP address. And this particular network is smaller with 256 addresses. So they can take their big, massive network and turn it into smaller
subnets. And that my friends is your first little glance into subnetting, which is what we're gonna really cover and dive deep into in the coming videos. And by the way, also what it here taking a class, a network,
and we cut it up and made it smaller with a different subnet mask. Other than its default, we call that a classless network. So for example, my home network is actually ten seven one zero,
a class, a IP address, or a class, a network. But my subnet mask is 2 55 dot 2 55, 2 5 0, making it a degenerate,
a classless network because we're breaking all the rules. We're not obeying this ABC to EFG stuff. That's basically what you're doing. Got no class. But if you do obey the rules and you use the default subnet mask,
then you're class full you're full of class. You're elegant, but you're no fun. Now I'm just kidding. Little bit. So anyways, back to our, our address ranges our classes. We focused a lot on class,
a right here and his subnet mask, giving a network, just a ton of IP addresses too many way, too many, which is again, it's part of the problem I have with IANA or the head Oprah.
They just gave away too many IP addresses. And then as we move down, you'll notice that class B has a different default subnet mask of 2 55, 2 5 5 0 0. So again, if we take this first network right here,
bring it on down here. It might look like this with the subnet mask of 2 55, 2 55, 0 0 locking in those first two numbers. Those first two octets,
those will always stay the same. But then these last two numbers, these last two octets can be anything they want between zero and 255, I'm talking 65,534 host or IP addresses per network.
So bummer you get less IP addresses, which again is way too many. But the flip side is that you get more networks with a class B IANA or queen Oprah can assign 16,382 networks because again,
a class B by default must have a minimum of a subnet mask like this. And then moving on down the line, we got class C, which will look the most familiar to you, right?
Cuz it's it contains your home network. And again, we'll take that first network here, bring it on over here, come on little guy with this default subnet mask and those first three numbers
they're locked in. Can't touch those Octas and looking very familiar. We have a total of 254 available IP addresses on that network. This is the best plan they should have done this with every single network.
Because with class C networks, we have a total available for queen Oprah to assign 2,097,150 networks.
So if they had done that with every class, we'd be okay, kind of maybe no, we wouldn't. We have a different solution because eventually we would've run out,
but we wouldn't have run out so quickly. Come on adventures of the internet. Why can't you just look into the future and anticipate our needs seriously? So that's class a, B and C.
We're about to get to the D and E which infuriate me. I mean, I don't get too angry about it, but it's still pretty stupid. But first I just wanna point out.
I hope that you're picking up that the job of the subnet mask is to help determine how many networks and how many hosts we have for each class. Class C gives us the most networks and the, and smaller hosts per network.
Whereas class a gives us too many freaking hosts per network and like only 126 networks. If you stuck with the, you know, class full subnetting or class full networks. But of course,
and you probably assume this nowadays, we mainly do classless networks to take advantage of the IP addresses we need to use. So anyways, I'm gonna officially say Iyana. That was a dumb idea.
And now we're stuck with your mistake, but it's okay. All we have to worry about is learning this chart, memorizing it, knowing what it is, and then learning something scary called I, I P V six.
We'll cover that later. So now let's talk about my biggest problem with this is that there are IP addresses that we cannot use. We just can't. We can't.
So class D E notice they don't have a subnet mask, cuz it doesn't matter. Class D IP addresses are reserved for multicast or you might see it written in one word. I never know.
All you have to know about those is that they're very important to networking and you can't use them right now. So don't worry about it. Just memorize what they are. And then class E networks.
These bad boys are mysterious. They are locked up in the department of mysteries, FBI, CIA. I don't know they are experimental.
So don't even think about touching those who they'll get in trouble and I'm just getting you can't touch 'em they they're untouchable anyways. So we can't use DNA. And there's one more, I don't know if you noticed this,
look at that shark, is there a number range missing? Can you find where's Waldo? I'll give you a hint. It's in between a and B and also here's the other hint, Dorothy, because there's no place like home. This'll make sense.
And I always gonna make sense here in a bit. I'm not losing my mind. You may have noticed that the range here ends at 1 26 and then picks back up and B at 1 28, making us go, huh?
Where the junk is 127. Like where to go. That's a lot of IP addresses just missing. That's an entire class, a network, which means we're talking 1 27, 0 0 with the subnet
mass 2 55, 0 0, 0, which leaves missing over 16 million addresses. Where are you guys at? You know where they are? They're on your devices. These range of addresses.
Anything beginning with 1, 2 7 are what's known as loop back addresses. You may have heard that term before. They're used for network testing and don't get me wrong.
I love me a good loop back address because you can use it to test your network. You can actually make sure that your computer's networking is working by pinging your loop back address. What am I talking about? Let's try it real quick.
If you're on windows, go ahead and launch your command prompt or type in windows. Key search CMD. It'll look like this on Mac Linux. It'll be terminal. And right here,
acro stand across the board type up in P I N G or ping space. 1 27 0 zero.one. Now, if you're like what the junk is, ping ping is what we use in it to see if something is alive and awake.
So for example, I on my computer might send a ping message out to network shock.com saying, Hey, are you awake?
And if network shark.com is awake and a alive and actually there in living, he should respond back with a response. It is by far the most common troubleshooting tool you'll ever use in it.
So looking back at our example here, we're gonna ping 1 27 1, which is an IP address that just is virtual and lives on your computer. And we should all get the same result. If you're working head enter, Hey,
are you awake? Yes, I'm awake. Heym are you awake? Yes. I'm awake. That's essentially what you're doing. You're just making sure that you can hear yourself,
but the kicker is and the just it's so stink and stupid. I don't maybe is there something I don't know about this here? Here's the problem? I think all we needed was just this one.
IP address 1, 2 7 0, 0 1 to test our Nick our network to make sure it's working. Cuz we just did that. But for some reason they thought we might need 16 million to do that because do
this, you can go ping 1, 2 7, 1 5, 1 5, 8, just a random address. And we get the same thing. We're pinging ourselves.
Our computer has 16 million virtual IP addresses ready to respond to itself. Why? Okay. It's okay. Chuck it's okay. So roughly 4.3 billion IP addresses and
we can't use a lot of them and a lot of them are mismanaged. Thanks a lot IANA. Thanks a lot. Head Oprah. No, it's fine. It's. Fun to learn this. It's fun to learn how our IP addresses were formed,
how they're organized into classes, B C, D E. And it's definitely something you want to commit to memory. So get those flashcards out, memorize the sucker.
It will come in handy your entire it career, and also pretty handy on any kind of test you might be taking here soon. Now I know this might all seem like doom and gloom. I,
some problems that we have with our current IP address space and why we are just out, we're done, but don't worry. In the coming episode, I'll show you the massive bandaid we put on our IP address situation and it did
solve the problem kind of, and then we put it even bigger bandaid on it to really solve the problem. But who knows what will happen?
I know I'm not being specific cause I really want you to watch that video. So go ahead, go and watch. It should be up here somewhere or maybe up next, over here or over here. I never know where to point anyways. That's all I have.
And also have you hacked the YouTube algorithm today? Let's make sure you do. If that like button subscribe, button and notification bill comment almost forgot.
You gotta hack YouTube today. Ethically of course. Yeah. That's all I have. I'll catch you guys next time now real quick in case no, this video is also part of my CCNA series designed to help you and prepare you
for the Cisco CCNA certification exam. That's a mouthful and the sponsor that entire series is boon software. So if you're looking at getting your CCNA, which you definitely should,
it's one of the best it certifications out there. Check out boon. They are without a doubt, the gold standard and prepping you for that exam. From practice exams to lab software, to courseware,
they have everything you need to get the CCNA and not just CCNA, we're talking CCMP Linux plus security. Plus they have it all. I personally used their lab software and practice exam software for the TSU
exam, which was part of the old CCMP and it was super hard, but I felt already from using boon. So if you're sitting here wondering, Hey man, I'm ready to take my security plus or my Linux plus or my CCNA,
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The internet's creators underestimated its growth and the explosion of devices needing IP addresses. Classful addressing wasted vast address ranges by assigning massive networks (like Class A with 16 million hosts) to organizations that didn't need them, while entire classes (D, E) and the loopback range were reserved for specific uses, further reducing usable space.
Classful addressing divides IPv4 into five classes: Class A (1.0.0.0–126.0.0.0) uses a 255.0.0.0 mask and allows 16 million hosts per network. Class B (128.0.0.0–191.255.0.0) uses 255.255.0.0 for 65,534 hosts. Class C (192.0.0.0–223.255.255.0) uses 255.255.255.0 for 254 hosts. Class D is for multicast, and Class E is for experimental use—neither supports host addressing.
Only one IP (127.0.0.1) is needed for loopback testing, but the entire Class A network of 127.0.0.0–127.255.255.255 is reserved, wasting over 16 million addresses. This is a prime example of poor planning in the original IPv4 design.
Large organizations were given Class A or B blocks, which provided far more IP addresses than they actually needed. For example, a company might use only 1,000 out of 16 million available addresses, leaving millions unused and unavailable for other networks.
Class D (224.0.0.0–239.255.255.255) is reserved for multicast traffic, and Class E (240.0.0.0–255.255.255.255) for experimental use. Neither can assign standard host addresses, locking millions of IPs away from public use and worsening the shortage.
Classless addressing (CIDR) replaced the rigid class system, allowing networks to be subdivided with variable subnet masks. This lets large allocated blocks be chopped into smaller, efficient subnets, delaying IPv4 exhaustion. IPv6 is the long-term fix.
Memorizing class ranges and default subnet masks is critical for the CCNA exam and foundational to grasping subnetting, CIDR, and IPv6. The mismanagement history highlights why modern tools like private IPs and NAT exist.
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