IPv4 5 transcript

Today we are going to learn how to find the network address, broadcast address, first IP address in the range, then last IP address in the range. Now first of all network address, what is network address? A network address identifies the entire network. Now look at here very carefully. A network address identifies the entire network, not a specific device. What does it mean? So that means you cannot assign a network address to a particular device like PC.

It has an IP address but there is something called network address which you cannot assign to a PC. This is not possible. Okay. It is the first IP address in the subnet. What is it? We'll have a look. In order to find it, if you make all host bits zeros, okay, in binary, then you will get it. Routers use it to identify the network. Now let's come here. Let's say this is an IP address. If you look at here, what kind of IP address is this is?

This is class C IP address. So for any class C, the cider is /24. The cider is SL24. If you convert SL24 into the subnet mask, you will find 255 255 255.0. Now look at here very carefully. What did I say? Whatever is the cider value is your network bits. Is your network bits. That means you have 24 network bits. So if you have 24 network bits, how many host bits you have? First of all, the total number of bits are 32.

And if you subtract 24 network bits, you left with eight host bits. So if you look at here, uh it has got network portion has 24 bits, host portion is 8 bits. Okay. Now if you convert this IP address into the binary it will be something like this. And if you convert this subnet mask into binary it will be something like this. Now look at here very carefully. There are 24 bits that are network portion. Now if you count you will find 8 8 is 24.

Okay. These 24 bits are network portion. There is another formula as well. Okay. The other formula is as long as you can see one as long as you can see one in the subnet mask. So if you look as long as you can see one in the subnet mask that means that's the network portion. The time you see starts with zeros that's the host portion. The time you see it starts with zero that's the host portion. Okay. Now uh I will show you something.

Okay, what I wanted to show you, let's say if you have a subnet mask, it will never be something like 255.0.0.255. It will never be something like that. It will always be let's say 255.255.0.0 or zero acceptable. The time you go to zero, you cannot The time you go to zero, you cannot go to any other number. Now look at here very carefully. We know that this cannot be and this can be. Let's look at here 255.1 192.0.0.

Can this be a subnet mask? Of course, it can be a subnet mask because the time you went to zero, you never went to a number anymore. Okay? So, in other words, if you look at here in the subnet mask when you are writing once the time, let's say you can stop here one and you can start zero from here. So, everything will be zero. That's completely fine. No problem. The time you start with zero, you cannot go back to one anymore.

Okay? And of course you know from binary you need to do the calculation for the um decimal. Now look at here this is the network portion and obviously this is the host portion. Never ever touch network portion. Network portions are fixed. You cannot change anything in the network portion. You cannot change anything in network portion host portion you can change anything and everything it doesn't matter okay so why this is the network portion first of all /24 24 bits so any any correspondence bits that you can see from the IP address comparing with the like subnet mask you cannot touch it okay because that's the network portion The only portion is the host portion.

What it says here, this is the most important one. All host bits zero. Now make all the host bits. Now exactly the same. You wrote the same IP address. This is the network portion. This is the network portion. And when you come to the host bits, make all host bits zeros. So if you make all of them zero, you will find 192 168 1.0. So the network is 192 168 1.0. Now look at here very carefully I gave you like think about the table the first number is zero and the last number of the table could be 100 could be 99 doesn't matter but it always starts with zero so if you look at here this is the first address of the subnet this is the first address of the subnet first IP address of the subnet and this is the network portion and sorry this is the network address and it cannot be assigned to a individual device.

Now look at here very carefully. Uh it may not be zero always. Okay? Depending on the circumstances it may not be zero. It may not be zero. Okay? Uh it depends on a lot of things. Okay? But you do like this whatever you get is the network address. Now let's look at broadcast address. What is a broadcast address? Okay. First of all, according to the definition of broadcast address, if your computer, this is a computer 19268.1.1.

This is another computer 19268.1.2. This is another computer 19268.1.5. Let's say in this way you have like 1 until 1. If this computer wants to send to all of the computers at the same time, he will use the broadcast address. So broadcast address is used to send packets to all devices in the subnet. So if it is used to send packets to all devices in the subnet, obviously it is clear that you cannot use it on a particular device.

So the network address and the broadcast address cannot be used it on a particular device. It is the last address in the subnet. Make all host bits once. Now let us work with this one. So this is the IP address and this is the subnet mask. We know the network portion. This is the network portion and you cannot make any changes in the network portion. The only changes you can make in the host portion. This is the host portion.

This is the where you can make any changes. So if you look at here you have once here you cannot make any changes on the on the top. However, if you have zero here, if you have zero in the subnet mask, you can make changes to the corresponding bits on the top in the IP address. Okay? So, if you have zero in the sub, if you have once in the subnet mask, you cannot make any changes in the corresponding bits. But if you have zeros, you are free to make any change.

Now, look at here very carefully. This [clears throat] is the same number. This is the network address. We know that last B host bits are zero. Okay. Set them to on. Okay. Now what you need to do actually here you need to set them one. So 1 2 3 4 5 6 7 8. So if you set them to one if you set them to one you will find 192 168 1.255. Okay. So if you take this number 11 one okay so if you do here uh binary to decimal conversion so 2 ^ 0 2 ^ 1 2 the power 2 2 the power 3 2 the power 4 2 the^ 5 2 ^ 6 2 ^ 7 and if you do that it will be 1 2 4 8 16 32 2 64 128 and if you give make them all once and if you add them you will find if you add if you add the values whatever is 255 is 255 okay and that is the last value that you can get and this is broadcast address and you cannot use it on any device.

Now let's look at here very carefully usable host address. First of all if you have two if you have eight host bits how many numbers you can produce from eight host bits there is a formula it's 2 to the^ number of host bits that number of IP addresses you can produce. Now if you do 2 ^ 8 is 256 IP addresses you can produce with 8 host bits. But there is a problem. What is the problem? There are two bits that you need to always subtract.

So 256 minus 2 it will be 254 usable IP. Usable IP. Why usable IP? Just remember there is something called network address. there is something called broadcast address which we cannot assign it on on any device. Okay. So we will have only 254 usable IP address. We'll have 254 usable IP addresses. Now look at here very carefully. The network address is 1.0. We already know that the broadcast address is 1.255. This is the first address.

This is the last address. They cannot be assigned anywhere. What will be the first usable address is 1.1. Second usable address 1.2. Third is uh the last host will be 1.254. Now here if you look at here very carefully this is the network portion. There is no change in the network portion. As I said you cannot make any changes in the network portion. This is the network portion. No changes. This is the network portion.

No changes. This is the network the host portion. So if you look at here this is the host portion. This is the host portion. This is the host portion. So host bits you can change it in any way and this number will keep on changing. Okay. Now look at here very carefully. Let's do something with class B. Okay. That was with class C. Let's do with class B. We know that for network address all host bits will be zero. Now look at here.

We have an IP address 10.6 Six 10/16. How can we understand it is class B? Look at the first octed. Look at the first octed. By looking at the first octed, you will be able to say it is class B or not. Check the range of class B. Okay. Check the range of class B. What is the range for class B? So if you remember for class A it's um 0 to 126 for class um okay sorry I made a mistake here 1 to 126 for class A is 12126 for class B is 128 to 191 for class C is 192 to 223 I think so okay now look at here very carefully This 172 lies between 128 to 191.

So this is class B. Okay, this 172 is class B. Now look at here very carefully. If it is a class B, what did I say? Because these are the things that you need to memorize. Okay, for class A, for class A, the default cider is slash8. For class A, the default cider is SL8. For class B, the default cider is SL16. For class C, the default For class C, the default cider is SL24. Okay. For class B, the default cider is SL16. 16.

The subnet mask is 255 255.0. Now look at here very carefully. If you get the binary of this 172, 1645 10, it will be something like this. Now what did you look at here is the subnet mask. The subnet mask is 255 255 0. So this is the subnet mask. What is the network portion? This is the network portion. This is the network portion and rest of this is the host portion. So you can this is your host portion. This is your another host portion.

Okay? Because if you see zeros in the subnet mask, any binaries corresponding to zeros on the IP address, you can change it. Now look at here very carefully. According to the according to the definition of the network address, make all host bits zeros. So this is a host portion. This is a host portion. Make everything zero. But you cannot touch here. So it will be the same. 170 to 16 0 0 0 170 to 16 0 0. Now look at here very carefully according to the broadcast address make all host bits zeros.

Now again this is the host portion. Okay. And this is the because everything is zero here. If this is the host portion make all host bits. So make all host bits once. Make them on. Make them on. Okay. So 255.255. If you do this one, you'll find this one. So this is the broadcast address for class B. So basically in class B, two octets will be impacted. Now usable host again you know that how many host bits you have in class B.

Class B / 16. So there are 16 network bits. Therefore you have total 32 - 16 is equals to 16 host bits. Okay, simple. The formula for finding the number of IP address is 2 to the power host bits which is 2 ^ 16. So you 2 ^ 16 is 65336 and you need to subtract two. Why you need to subtract two? Because there is a network address and there is a broadcast address. they cannot be assigned to any device. Okay. So you will have these many usable IP address.

Now if you look at here according to the formula 0 0 is the network address. 255 255 is the broadcast address. Now look at here very carefully. People sometimes they get confused. If I give you 0 1, what will be the second number? 02. What will be the third number? 03. So if you look at here this zero remains fixed. Okay, you cannot make any changes in this zero. But 1 2 3 will keep on changing. So if you look at here this zero will remain fixed but 1 2 this will keep on changing. 254 is the um so if you look at here you will reach something like this 172.16.0.1 0.1 172.16.0.2 172.16.0 The max it can go is 255.

Is this a broadcast address? Is this a broadcast address? The answer is no. Why? Because we already know that this is the broadcast address 255.255. But here you have 0.255. So this is an IP address. Now look at here. Once it reaches 255, it cannot go to 256. So what will happen? It will become 17216.1.0. Is 0 network address? Is it a network address? The answer is no. Why? Because we already know that 0 is the first address and which is the network address.

Then it will become 17216.1.1. Then it will become 17216.1.255. Then again it will increase one. So it will increase 1726.2. So when it reaches 2.255 it will become 3.255. Then it will become in this way it will keep on increasing. Now look at here very carefully. If it keeps on increasing like that you will have one day 1716 dot. 255. 255 and after that you cannot make it 256 and you cannot make it 256. You cannot change it anymore.

So this is the broadcast address. You already know that this is the broadcast address. The first usable address is 0.1. Last usable address is 255.254 because after this you will have 255.255 and you will have no more. So this is the last usable host. Now again come to class A. So according to the formula I said 10 it starts with 10 1 to 126 is class A by default is SL 8 /8 means there are eight network bits. So how many host bits you have 32 minus 8 network bits.

So you left with 24 host bits. So if you look at here the maximum number of host bits that you can have is in class A because you have maximum number of host bits. Okay. Now let's come here. This is the IP address and this is the subnet mask. The network portion is this. Can you make any changes in the network portion? I cannot make any changes in the network portion. However, if you look at here, the host portion is this.

Why? Because you have zeros here. In correspondence, you have zeros here. You can you can make any changes in this portion. This is your host portion. Whatever you want you can make it here. Now according to the formula set all the host bits zeros. So if you make everything zero you will find something like 10.0.0.0. And this is the network address. This is the network address. If you look at here this is the network address.

Okay. Any questions? No. Okay. Now look at here very carefully. Broadcast address make all host bits once. So if you come at here the same thing. If you come at here, this is your host portion. Make all the host bits once and it is 10.255.255.255. Okay. So this is the host portion. This is the host portion. This is the host portion. So you make everything zero in the host portion. You get 0 0 0 because you cannot touch the network portion.

Okay. Now again the formula is 2 to the power the total number of IP address you can produce 2 to the power h. The total number of IP address will be 2 ^ 24 which is 216. Now there are two addresses one is the network address another is the broadcast address that cannot be assigned to any device. So you need to subtract two from here. So 214 will be the will be the these number of usable IP address you can produce these number of IP addresses and you can assign it to the users.

Okay. But however this is the total this is the total. Now again if you look at here very carefully the network address all host B zeros the broadcast address all host bits once. Now look at here very carefully 10.0.0.0 what will be the next number? 10.0.01. In the same way you will go to 10.0.255. Then you will find 10.0.1.250. Okay. Then you will go 10.0.1.255. Then when it is 255 it will keep on increasing 10.0.2.255 like 2.02.12.2 2.3 2.255.

In the same way it will keep on increasing and when it reaches 255.254 this is the last usable IP address. This is the last usable IP address. After 254 it will become 255 which makes the broadcast address and that will be the end of this address range that you can assign on the user. That will be the end of this address range that you can assign on the user. In this way you can calculate the fifth usable host. The second last usable host you just have to take time and you just need to find all these things.