 Hello, dear learner friends, welcome to this video session part 2 of Network Layer IP Addressing. Myself, Mr. Vipul Kondekar from Walton Institute of Technology, Sholapur. These are the learning outcomes of this session, so you will be, student will be able to get the concept explore classless addressing, so what is comparison between classful and classless, identifying the class as well, how we can differentiate between the network address and host address, so you will get that skill after attending this particular session. So these are the contents where we will go for understanding the address blocks used for the classful representation, then we will go for some special IP addresses used, and then we will go finally for classless IP address representation, and then how we can separate the network ID part and host ID part in classless representation with the help of cider representation, classless intradomain representation. Now we know that when we go for classful representation of the IP address, so there are three types of what we can say consumers were expected, so very big small on moderate, see but the point is when you talk about class B type of address, it assumes that you will be having 65,534 number of hosts, class C says that you can have at the max 250, 254 number of hosts, now this class B is too big for the most of the organizations and class C is too small, so can we have something in between that, so that is the need of classless IP address representation, because in classful IP addressing you will have two levels of hierarchy that can be increased to three level by using subnet, but still you will find that the classful addressing is inflexible, because if you have a company with around 2000 hosts, so then class A and B if I go for, so I will be wasting most of the IP addresses and if I go for class C then class C will not be sufficient, so what can be the solution in that case, so later they come up with the classless IP address representation and classless IP addressing is a special, classful IP addressing is a special case of classless addressing itself, so what is done is as in classful addressing the addresses most of the large part of the address is wasted, so we are trying to minimize that particular wastage, we want to efficiently utilize the IP addresses, so the classful is almost absolute, what is getting used in current days is classless representation itself, now who is giving you the IP addresses, when you want to get connected to the internet, when you want to get connected to the internet ICANN is the authority, internet cooperation for assigned names and addresses, this is the authority used for giving the addresses, so now we will try to understand what was the problem, so if you look at these blocks you will find that this is the block representing the situation in case of class A type of IP address where you will find that in class A type of IP address you can have around 127 different networks because the network ID is of 7 bits, 1 bit is used for identifying the class itself and then within a network you can have 2 raised to 24 different hosts, so within the network huge number of hosts are possible, so in general you may say that you can have 128 blocks with these many number of hosts in each block, so if you look at class B what is happening is the network ID is increasing means number of networks you can have will go on increasing and number of hosts are slightly less than class A you will find that you can have these many blocks with around 65,536 addresses in each block, like that in class C also, you class C you can have more networks you can have 2 raised to 24 different networks in case of class C, but within a network you can have 2 raised to 8 different hosts, so 256 addresses are possible in class C, but summarizing the thing what happens is it is observed that millions of addresses are wasted when you go for class full representation as far as the class A are concerned, many are wasted many addresses are wasted when you go for class B and then in class C the problem is the addresses are smaller than the need for most of the organizations, so there is problem with the class full addressing, so class D and class E they are reserved for future use class E and class D are most of the spatial IP addresses which we are going to discuss now, and this is one of the reason why we go for again class less IP address representation, so now let us come to this point what are the spatial IP addresses, so these are the spatial IP addresses where how we can identify the spatial IP address is the if the host ID is all zeros then it is a spatial IP address you are talking about the specific network, so this you will understand with the help of the diagrams which are there in the next slides and there are some IP addresses which are called as addresses for the private network, so those can be freely used other than these IP addresses you need to pay for ICANN to get the IP address for getting connected to the internet, so let us concentrate again on some spatial IP addresses, so this is the if this kind of address is there then this will be the network address means all host ID bits are zero means you are talking about a particular network, so just if you look at all these addresses means host ID part is zero class C representation means you are talking about this particular network, then there can be an IP address of kind called as broadcast direct broadcast IP address, so how it will appear in the host ID part all the bits will be one, so if you look at this IP address, so if you find the IP address destination IP address, if you are finding that 221.45.71.255, so you understand it is a class C address and then 255 means all host ID parts bits are one, it indicates that that packet you want to forward to all the host within the network means this is the broadcasting and that broadcast packet will never go outside network means when it goes to the router, so it will kill that particular packet, so packet will not go outside but within the network it will be broadcasted if this is the all ones are present in the host ID part, so like that sometimes you can have a limited broadcast, so limited broadcast means all ones means IP address with IP address 255.255 that sort of IP address 255.255.255.255, so that will be IP address of kind limited broadcast, so now some IP addresses are used for address resolution, so this is a special IP address when it is talking about the discourse on this network, so you are concerned with getting if you don't know your IP address you will use this type of what we can say IP address and then there is one special specific host on this network, so if you are interested in talking to a particular host within your network then the network ID part of that IP address will be zero and just you will be talking about the you will be giving host ID part in the destination, so if this is the destination means you want to communicate with the host within the network having the host ID part 64, so this is how the communication will be taking place between the two hosts within the network, so there can be one interesting IP address which is called as loopback address where the first byte will be 127 and remaining bytes will be as it is and if it is a loopback address what exactly happens is it is not crossing to or it is not going to some another node but what it is doing what that packet will do is packet will be again forwarded to the same host means the source and destination it is again coming to the same host, so this is called as loopback. Now let us try to understand how the problems with the classful addressing are solved with the classless addressing, so in classless addressing what we are doing is the IP address is represented in the cider format, so IP address is of kind VLSM means variable length subnet mask is supported for these kind of IP addresses and this is the format of representation, general format where the decimal format dotted decimal format representation of IP address will be there and that will be preceded by slash yun and where this yun is the number which indicates how many bits of IP address are corresponding to the network ID part okay so and then easily you will be separate out how much is the network ID and how much is the host ID and for IPv4 version this yun can take values from 1 to 32 and then when you have this value of yun as 1 it is equivalent to you have a mask of this kind 128.0.0.0, so these are the equivalent mask for all these values of yun okay, so this is how the CIDR representation where there is no class for the IP address just a separator slash yun which indicates how many bits that yun will indicate how many bits of the IP address will be representing the network ID part and remaining bits will be representing the host ID part obviously. So let us check your understanding with this read this problem so given this IP address what is the first address in the block what is the first address in the block so if this is the network address represented in classless representation side of format this is slash 27 what it means out of 32 bit IP address 27 bits will be representing the network ID part if 27 bits are representing the network ID part how many bits will be remaining remaining will be five bits and those five bits will be representing the host ID part and now if I want to get the address of the uh means address in the block first address in the block how I can get that is this is the IP address I can take that IP address I can represent in the binary format and then I will take the help of mask now mask is mentioned indirectly here slash 27 means 27 once will be there in the mask and that's why those first 27 bits will be as it is and what about remaining bit as you want to find out the first address of the block so I assume that remaining bits are zero okay the remaining bits are zero and then that will uh with that you will come up with the first address as 167.190.1.170.64 64 is what it is the decimal representation of this value okay so this will be the address of the this will be the first address in the block okay so this is how this CIDR representation is used one more example is there where try to find out how many addresses will be there in the block so now again if you understand how CIDR representation is there so given this is the IP address slash 20 indicates that 20 bits will be representing the network ID part so if 20 bits are representing 20 out of 32 are representing the network ID part what remains are the 12 bits okay and then 12 bits will corresponds to 2 raised to 12 means 4096 different hosts so how many addresses you can have within a single block will be 4096 so this is how the class list representation can be done with the help of CIDR representation where slash n and n will be indicating the number of bits representing the network ID part so with this we will stop here these are the references used for this video presentation thank you