Hello, I’m Sourav Khanna. And welcome to our new article on the introduction to ipv4 part two. Today we’re going to talk about classes of ipv4 addresses. And then we’re going to move on to Classless ipv4 addressing and we will conclude with a brief discussion on subnetting ipv4 addresses. There’s a whole lot of technical information to cover, so let’s go ahead and begin the session. Let’s begin by talking about classes of ipv4 addresses.
What is IPV4?
Internet Protocol Version four ipv4 is a binary addressing scheme that’s used for networking. It was initially finalized as a standard in 1981. ipv4 is a common network addressing scheme that is still being deployed today. There is an issue though with ipv4. Because of its structure and the growth and popularity of the internet.
Most of the world has run out of assignable ipv4 addresses. But thanks to some forethought, it’s still a valid scheme.
Today, we need to talk about classes of ipv4 addresses and we begin with a class a network address. Class A networks have an address range of zero to 127 in the first octet, which gives us addresses from 0.0.0.0 up to 127.255.255.255.
The first octet on the left has a binary representation that always begins with a zero. This gives us a possible 16,777,214 host addresses and the subnet mask with a class a network is always 255.0.0 dot zero then there are classes B network addresses, they have an address range of 128 to 191 in the first octet, which means that class B networks can have a range of 128.0.0.0 up to 191.255.255.255. The first octet on the left always has a binary representation that begins with one zero.
Now Class B network addresses give us a possible 65,534 hosts in the subnet mask used with a Class B network is always 255.255.0.0. Then there are Class C network addresses and they have an address range in the first octet of 192 up to 223. That means that we have an address range of 192.0.0.0, up through 223.255.255.255. And that first octet on the left always begins with one zero.
Class C network addresses give us a possible 254 post addresses or node addresses and the subnet mask with a Class C is always 255.255.255.0. The last class of address that you need to concern yourself with is the Class D network address. It has an address range of 224 up through 239 in the first octet, which means that it can range from 220 4.0.0.0 up through 239.255255255.
That first octet on the left has a binary representation of 1110. So the first four bits are always taken and they are always 1110. Now subnet masks are not defined for class the networking class and the network addresses are used for multicast communication. And finally, we have a special class of addresses Well, kind of a class of addresses, and that involves automatic private IP addressing up PIPA.
In some cases, the Dynamic Host Configuration Protocol DHCP process may fail. In these cases, a node or host will self-configure an IP PIPA address. Now within a PIPA address, the first two octets are always 168.2 54. And if you see that in your IP configuration, you know that you have a DHCP problem. So one of the first methods that they use to conserve the ipv4 address space was they broke them out into public and private IP addresses. public IP addresses are routable.
And being routable means that each public IP address is unique. There can only be one. Now public IP addresses are not flexible, you are assigned to your network space, and you’re not really given a choice of what your public IP address is going to be.
And then there are the private IP addresses. These are non routable. They do not need to be completely unique throughout the world. They only have to be unique on their network. The first one that we’re going to discuss is the class a license, there is only one class a license, you have a possible address range of 10.0.0.0 up through 10.255.255.255.
Next up is the class B license. There are 16 possible network addresses, not networking O’s, but just network addresses available in a Class B license. They have an address range of 172.16.0.0 up through 172.31.255.255. And last but not least is the class C license. There are 256 Class C licenses with a possible address range of 192.168.0.0 up through 192.1 68.255.255.
Now private IP addresses are highly flexible. You get to assign the network space it’s not assigned to you. Now let’s move on to Classless ipv4. Addressing Now the classes of addresses actually limited the flexibility of ipv4. Part of the reason for that was that the first routing protocols required the class structure. And you would think that with over 4 billion possible IP addresses we’d still have flexibility, but we really didn’t. classless addressing, which is called classless inter-domain routing or cider was developed to slow the growth of routing tables.
It also slowed the exhaustion of ipv4 addresses, it also created much more flexibility, the subnet mask becomes fluid, and it’s not rigid with cider addresses. It does not affect the private address space ranges though, even though the subnet mask is now fluid, you still only have those range of addresses available with the introduction of classless addressing subnetting is now possible, and it’s highly desirable.
So let’s take a look at how cider notation works. And we’ll begin with 190 2.168.9 with a subnet mask of 255.255.0. With that becomes is 190 2.168.0.9 slash 24. That slash 24 represents all of the ones in the subnet mask. And that’s those first three octets on the left that 255.255.255. And if you look at that address, it’s a Class C address, which always has a 255.255.255.0 subnet mask, but it now becomes fluid with cider, we can take it and we can make it a 190 2.1 68.1 28.0/23.
And what that really represents is that slash 23 is a subnet mask of 255.255.1 28.0. And that gives us a network of 190 2.1 68.1 28.0 which actually gives us a host range of 190 2.1 68.1 28.1 through 190 2.1 68.129.2 54. That gives us 512 host addresses as opposed to the possible 254.
Now the broadcast address for that network would be 190 2.1 68.1 29.2 55. So now let’s move on to subnetting ipv4 addresses. So what is subnetting? Well, subnetting cuts address spaces into smaller pieces. It takes one range of addresses and splits it. This creates flexibility and network design and creates efficiency in addressing space utilization. So let’s take a look at an example of subnetting. This will involve a small office network.
So originally, we have a network address of 223.15.1.0/24. This is a Class C private network and it gives us a possible 254 hosts available. Why only 254 will be because a host cannot be assigned to the network address which is 223.15.1.0. And it can’t use the broadcast address which is 223.15.1.255. In this example, with this network address, all the hosts in the network can see all the other nodes.
Now let’s say that for security considerations, you want to split this into two networks. Well, you can do this using subnetting. So what you do is you take that slash 24 network and you create two slash 25 networks. And those would be 223.15.1.0/25 and 223/15.1.128/25. In this situation, the first network’s host address range would be 223.15.1.1 up through to 23.15.1.126.
And why is that? Well, because you can’t use the network address which is 223.15.1.0. And you can’t use the broadcast address which is 223.1.1 27. The second address range that would be created through this subnetting process would give us a host range of 223.15.1.129 up through 223.15.1.254.
That’s because you can’t use the network address which is 223.15.1.128. And you can’t use the broadcast address which is 223.15.1.255. Each of those subnets would have 126 possible host addresses. So you took your possible 254 hosts available in one network, and you broke it down so that you now have two separate networks, each that are capable of having 126 hosts. And that’s an example of subnetting an ipv4 address.
Now, that concludes this session on the introduction to ipv4 part two, I talked about classes of ipv4 addresses. I then moved on to Classless ipv4 addressing and we concluded with a brief discussion on subnetting ipv4 addresses. Good day.