IPv4 1 transcript

Okay. Um, we'll be starting with IPv4 address. Let us have a look at it. Um, IPv4 address. Now, it's a 32bit logical address assigned to a network device. The few words that we want to focus here is 32 bits. The first thing that you need to understand what is a bit. I think you already know. So bits are something like zero and one. So zero is one bit. One is one bit. Okay. Now when I say each of them is a bit when I say 32 bits that means you have a combination of 32 zeros.

Like it's a combination of zeros and ones but it has to be 32. So let me just do like this way. Let me just write um something uh 0 1 0 1 0 1 0 1. Let me uh also write something like 1 0 1 0 1 0 1 0. Let me write something like 0 0 0. Let me also write something like one one one one one. Okay. Now uh you can see like I have put some gaps between them. I will come to that point later. Okay. So don't worry about it. Logical address means it can be assigned to any device at any point in time.

Okay. Um now that's not true. Okay. But I'm just saying logical. Okay. Um, so you can assign it. Okay. Now like that is what we are going to learn. Okay. Uh, with time like what IP address you can assign where and what IP address you cannot assign where. Now look at here very carefully. We configure it on a network device and mostly it will be configured on an interface. The another name could be port. The another name of the interface is port.

Okay. As well um so you can configure it on a port. You can configure it on an interface. They're the same thing. Okay. If you look at here is written in decimal format with four octets separated by dots. Now for example 192 168 1.1. Look at here very carefully. This is binary format. And what is the decimal format? It will be something like this. 192 1681.1. Let me write here. What's the decimal format? 192 168.1. It is the decimal format.

Now if you see something like um like 1 2 3 4 5 6 7 8 9 10 whatever is the number that means that's the decimal format. And if you see zeros and ones that means it's a binary. Now don't get confused like this one is a binary. Okay? because it you can look at the pattern and you can see it's like 190 to 160. It will be not something like 0 1 0 1 binary. Okay. So you cannot have a combination of binary and decimal. For the purpose of understanding I may use combination of binary and decimal because the reason is if I want to write everything in binary let's say if if I have 128 bit and if I which is IP v6.

Now if you look at here this is IP V4 which is 32 bits and IP V6 this is something you'll not read now maybe at a point in time then it will be 128 bits okay so I won't be able to write 128 bits like 0 1 0 1 0 1 and all like this way okay so in that case I will put for the purpose of understanding but when you write decimal it's completely decimal when you work with binary it's completely binary now the question Is is this 192?

No. Is this 168? No. Is this one? No. Is this one? No. So I just wanted to give you an example the difference between binary and decimal. So this is surely not 192. This is surely not 168. This is surely not zero. This is surely not one. Okay. Uh now you know what is binary and decimal. But however if you convert this it will be if you convert this it will it will produce a decimal. If you convert this it will produce a decimal.

If you convert this it will produce a decimal. If you convert this it will produce a decimal. And that decimal and if you look at here what it says it's a four octets. Focus on the word octets. Octets means eight eight bits. So that is why I actually put them in this way and they are separated by a dots. So if you look at here, so you will get a dot here, a dot here, a dot here. And if you come, if you look at here, there are eight bits, there are eight bits.

So that is called octets. If you add them all together, you will find 32 bits. Now, um u we will learn conversion later. We'll we will run we will learn conversion later but for the time being not okay. Uh I don't want to put everything in one place. Just have a look here. Okay. Now if you look at here very carefully um what will be the decimal format of this number? So it will be I think if I'm not making a mistake 85.

Okay look uh we can do this conversion like um once we do the conversion like we'll have a look at that one later. uh but for the time being I think it will be 85 and it will be 170 it will be zero and it will be 255. Okay, the conversion is will look like this. And in the same way the conversion of 85 will be this to binary 170 will be this, zero will be this and 255 will be this. Okay, I think you've got a little bit of idea what's um IP address and what it looks like.

Okay. So if you look at here every number can be represented eight binary bits. It is already clear. So every number is eight binary bits. Eight binary bits. Eight binary bits. Eight binary bits. And hence we call it an octave. Now if you look at here the total number of possible IP addresses is 2 to the power 32 because um you have got 32 bits. Okay not all all IP addresses are usable or routable over the internet. Now this is important.

If you come here for this particular line, there is something called private IP address which is 32 bits and there is something called public IP address which is also 32 bits. There is no problem. They they they all look the same. Okay. So what is private IP address? They are not routable on the internet. They are only used on LAN. Okay. and public IP address. You see not all the IP addresses are usable or routable over the internet.

Okay. So public IP addresses they are routable over the internet. Okay. Now what happens if you want to route a private IP address over the internet? Your ISP will block it because internet is something that you don't control. It is controlled by your ISP. Now when I'm saying about ISP, think about Optas, think about TPG, think about uh T uh Telra. Okay, it is for free and it is you need to pay for it and uh like you can write any of the private IP address there there are private IP address range and it's up to you it's up to you but this is something is not up to you.

It is up to the ISP what the ISP gives you. Okay? So, you cannot uh you may request for an IP address. If they have, they will give you. If they don't have, they can't give you. Okay? Now, IP IP V4. Now, look at here very carefully. Don't get confused with this public and the private IP address. IPv4 can be divided into five different classes. Okay? So, private and public is of course there. But IPv4 addresses can be divided into five different classes A, B, C, D and E.

This is something have to be memorized. And if you look at here very carefully like just remember IPv4 address like the lowest you can have in the address is zero and the highest you can have in the address is 255. And if you look at here very carefully, you see all zeros produces only zero and all once it produce only 255. So actually you cannot have less than zero and you cannot have more than 255. So if someone gives you an IP address which is more than 255, it's an invalid IP address.

Okay. Now this is the range for a 0.0.0 to 127.255.255. 255.255. Now let me take this number and look at here very carefully. The starting or the first one is 0.0.0.0.0 and the last one is 127 dot 255 dot 255 dot. 255. Now look at here. If someone gives you an IP address which is 1.5.200 and someone gave you another IP addresses which is uh 195.0.2.1. The first thing that you will try is this IP address. You can fit in between this or not.

If you can fit this, this is a class A IP address. Can I feed this IP address in between? This is a class A. I know that. Can I feed this IP address in between them? 195. So it says the initial is zero and the last one is 127. Can I fit 195 between 0? No. 195 is beyond 127. So this is not a class A. This is not a class A. So this is how you know an IP address belongs to which class? An IP address belongs to which class.

Okay. Similarly, you need to memorize for class B is 128 0000 191 255.255.255. For class C 19200 to 223 255.255.255. Now mostly we will be working with these three classes. Okay. Class D is reserved for multiccast. It is mostly for voice and video. Okay. So if you do CCNA collaboration, okay, CCNP collaboration, you will need about this one. And class C is used for experimental purpose which you can say research and development.

Okay. So mostly you will not be using class D and class C. However, you need to know what is class D and class C is and the range. Okay. But however, we will not use them. Okay. I think so. If you want to assign an IP address to a device, you'll have to choose from either either one of them. Now from each of the classes we have some IP address like public or private. So um we will learn those things okay in uh in one of the videos we'll learn u in one of the classes we'll learn uh what is the public IP address and what is the private IP This okay there is something called RFC 1918 uh 1918 address.

RFC is a standard 1980 address. So this is this standard has been given to the private IP address. Now look at here very carefully in each of the three classes you have a block of IP address that is reserved as the private IP address. We already discussed what is private IP addresses. A few characteristics of the private IP addresses is not routable is not routable over the internet. Very important over the internet.

Uh it is routable inside. Okay. not over the internet. Uh inside means inside the land. It is used only in the land. Okay. Uh it is for free. Uh as long as you know how to create that one, okay? How to use that that one, you can produce your one as well. Um you can produce your one. Uh you can have duplicate IP address. You can have duplicate IP address. You can have duplicate IP address in different lens. Not in the same in different okay in different lens but not in the same not in the same length.

Okay. Now look at here very carefully. Um, IP address is a number that actually identifies a device. So, if you have two devices with the same number, let's say you have two devices with the same number and they're in the same location, then uh how can you identify who is who. Okay, so that is why you cannot have this. So, you can have a different number. Okay, as long as there are certain rules, okay, you need you can follow it, it will work.

Um, yes, they can be used by anyone, doesn't matter. Uh, RFC90 address helps to conserve the Okay, now look at here very carefully here. Why we need private and why we need public? That's the first question. Like why does the private exist? If you look at the IP address, okay, if you look at this IP address thing, like there is a limitation. there is only 32 bits. Okay? And you can have 2 to the^ 32 like um how many uh like I don't know like something million or something.

But if you look like a person is using 10 20 devices even the watch is having an IP address. Even the refrigerators with the IoT everyone is having like at a home you go they need 100 IP addresses. Okay. So if you are not having the private and if you are not having the duplicate IP addresses then you will run out of you you would have run out run out of IP addresses a long time ago. So that is why we actually need u public and private because public IP addresses are unique unlike the private IP addresses and uh there is no duplication of the public IP addresses.

I think um it should clear a little bit about the private IP addresses. It is very important. It is always um now the question comes um what are the private IP addresses. Okay. So we need to know like we need to create the public IP address. We need to sorry we need to create the private IP addresses and we need to use the private IP addresses at our home. So we need to know the range. Now look at here very carefully.

This is the range for the private IP addresses. The first thing you come here. You come here. You get this one. Okay. Let's get this one. Um. Okay. Let's get this one. Let's get this one. Copy this one here. Bring it here. Put it here. Now look at here very carefully. The whole thing is the the whole thing is the class A. So in class A so if you look at here if I write this number 10 dot 0 dot 0.0 and it is 10 dot 255.255.255 it's the this is the full class A and this is the private portion of the class A.

Now look at here very carefully you see where is so if you look at here where is one where is two where is three where is four where is five they're missing so they are the part of the public IP address they are the part of the public IP address so if you compare here it's 10 and here is also 10 so is there any range like for example think like it is 12 so if it had been 12 so there had been a range of two right like two numbers 10 11 12 actually three numbers but there is no range here right so it's all 10 okay so only any number that starts with 10 is a private IP address and if you look at here this is the private IP address you memorize the range for the private IP address you memorize the range for the private IP address and any number that is not a part of the private IP address is a public IP address public IP address of which class A, B or C the public IP address for class A.

Okay, depending on what you have here. In the same way if you come here and if you take this one as well um class B, class C. Okay, as well. So if you take here class B C because that is what we need only. So if you look at here 128 to 191 but if you look at here it is 172. It starts with 172 here which is 172 and it also ends with 172 here. Okay, which is 172. So if you find but here you have range right. So any number in this block of IP address matches with this IP address is a private IP address.

Private for whom? Private for class B. Private for class B. In the same way this is class C. So if you look at here this one to this one 192 to 223. So if you look at here sorry this is class C address. This is the full class C address. However, the private portion is 192.168.0.0. Now, very important to understand here. If you get a number 192.170.0, this is not private. This becomes public. Why this is public? Because if you Okay, now there is a question here.

We didn't write the N1. So, you might get confused. So the end one is 192.168.255.255. So if you look at here very carefully the first portion matched 192 yes 192 match 168 and 168. So if you look at here 170 doesn't match with either of the 168 because this is the starting number this is the ending number. So actually this is the public IP address. In this way you can find a number whether it's a private IP address or it's a public IP address.

Now there is something called loop back address. The loop back address is always fixed. The entire 127.0.0/8. What does it mean? It starts with 127.0.0.0 and it ends with 127.255.255.255. So the entire range. Okay. So this is the starting. So if I get a number which is 127 50.60. So if you look at here this number fall in this range 127 matches with 127. All good. 190 is it between 0 to 255? Yes. 50 is it between 0 to 255?

Yes. 60 is it between 0 to 255? Yes. So this fall in this range. So enter block is the loop back address. Now look at here very carefully. The concept of loop back address is very complex. But however in order to make it simple and whatever you need to know initially is loop back address is uh is own IP address. So if you have a computer, your computer will of course have an IP address which is private IP address and it could be let's say 192.168.15.

In addition, the whole lot of IP address that you can see here. Okay. The whole lot of IP address you can see here is also his own IP address. So any loop back address which is which starts with 127 okay um is the own IP address okay so this computer has maybe a few thousands or millions IP addresses of it own now look at here very carefully loop back address concepts goes beyond we are not going into that so any loop back address is like um um if you ping actually if you ping uh it actually come backs to you okay so if you ping uh 127 7.0.5.6 it will come back to you.

If you ping um 127.255.255 it will actually come back to you. So all the IP address in is in this in this range belongs to the own device. So if you have 100 devices let's say if you have 100 devices all the devices will have the same thing. They actually don't go from one device to the other device. they actually comes here. So if you can if you ping like if this person pings 127.0.0.1 it comes to him. If this person pings 127.0.0.1 it comes backs to him.

If this person pings the same number 127.0.0.1 it actually come backs to him. This is the concept of the loop back address. But however you can see loop back address like 1.1.1.15. Now I said don't worry much about the loop back address just for the time being uh initially you just need to learn about this in the loop back address.