3. IP Addresses Network Classes

okay hello and welcome to this tutorial we're going to talk about IP addresses and network classes now the idea or the concept of network classes is one that is very fundamental to your overall understanding of how IP addressing works it's going to be something that is part of the conversation from this point going forward so as long as your network administrator dealing with IP you need to understand Network classes so that's what we're going to address today and in the last tutorial we discussed the concept of grouping IP addresses together and we now know that an IP address has a network portion which identifies the group itself and then it has a host portion which identifies each member of the group well ask yourself this question are all networks everywhere in the world the same size well you can probably guess the answer and that is no not all networks are the same size and so when IP was defined they also defined classes of networks along with it and we're going to look at three classes of networks that were defined in IP we're going to start off with the class a network and Class A networks are very large networks and then we're going to talk about the Class B Network Class B networks are more of your medium-sized networks not as big as your Class A and then finally we're going to talk about Class C networks which are for a small size network so they're not quite as big as Class B we're going to go through each one of these and figure out what they mean and how they're useful to us in understanding IP as a whole all right so let's get started and take a look at Class A networks Class A networks are very large networks now how do we know this well the network portion of an IP address is limited is limited to just the first octet okay so that means if we have four octets the first octet is the network portion and then octet two three and four are the host portion so if we look at an example I will write that write down a network number and as we discussed before a network number is the ID which represents a particular IP network and here the first octet is 10 and that is the network portion which means octets 2 3 & 4 are the host portions now why is this a very large network because we have three octets available to us to number hosts so there are a huge number of hosts available in a class a network in a little while we're going to look at all of the the sizes of these networks and you'll get a better understanding of just how many hosts you can fit into a single class a network all right so that's class a very large the network portion limited to the first octet let's take a look at class B's now Class B networks are considered medium-sized networks so they're not as big as a Class A yet they're going to be bigger than a Class C so they're right in the middle now the network portion of a Class B is the first two octets which means the host portion has to be the second two octets in other words octet Sri and 4 so we kind of split the IP address in half the first half is just for the network portion and the second half is just for the host portion if we write out an example here 172 dot 1600 so the first two octets are for the network portion so you can see because we have two octets as opposed to one octet in the Class A we can actually create more Class B networks because we have more room we have a whole second octet in order to create more of them however each one is going to be smaller than a Class A because there's less room in host portion of a Class B Network all right so we can create more Class B networks however each one is going to be a little bit smaller than a class a network all right let's go ahead now and take a look at a Class C Network Class C networks are considered small networks especially when compared to a Class A or Class B so with a Class C the network portion is the first three octets that means we're only left with one octet the fourth octet for the host portion I'll write out an example of a Class C Network 192 168 dot 1.0 so here the first three octets are all dedicated to the network portion so again we can figure out that class C's we can create more class C's because we have yet another octet the third octet now dedicated to creating class C's so we can create a lot more of these and we can ease and B's yet each Class C is going to be small because the host portion is as the single octet and remember an octet has a maximum value of 255 to illustrate the differences of the three classes of networks you can see here how each octet is dedicated so Class A you just have your single octet for the network portion whereas Class B and Class C have two and three octets dedicated so from this point of view looking at it illustrated like this you can see why a Class A is so big because you have three octets for hosts when you win you compare it to B and C just two and one likewise going in the other direction a Class C you can have so many of the Class C networks because you have three octets dedicated to making them whereas Class A just has a single octet for the network portion maybe you're wondering well how do you know if the IP address you're looking at all within a Class A B or C network well here's the answer each class has a range in the first octet that's dedicated to it so if you're looking at the first octet of an IP and the number falls between 1 and 126 it is a class a network likewise if it falls between 128 and 191 it's a Class B and 192 to 223 is a Class C so if you're looking at the number 172 you know it falls within the Class B range therefore it is a Class B Network in the third column here we've listed all of the the network numbers so you can see 1 thru 126 128 to 191 to 5500 and that's because class B's can occupy the first and the second octet so that's why you're including the second octet in the maximum range value there likewise in Class C the range is 192 0 0 0 all the way up to 223 255 dot 255 because because class C's can occupy the first 3 octets for the network portion okay so you have to memorize this chart because you have to know just by looking at an IP which class it falls into so again you'll always be looking at the first octet to determine that well pause the video write this down and commit it to memory and then when you're ready come back and we'll look at the next chart if you're wondering exactly how big are the classes in terms of networks and hosts well this chart here gives us an idea so if we look at the second column total number of networks we can see the formula and we can see the answer for each one and you can see the numbers are pretty pretty big so starting with a Class A two to the seventh minus 2 you get 126 and that makes sense because our range is from 1 to 126 now because we only have one octet dedicated to the Class A relatively few networks available to us that are in the Class A range however now if we move down to Class B you can see because we have two octets available to us that number grows significantly so there are a total of 16384 Class B networks available it's a pretty big number however it's not even close to as big as a number of class C's because we have three octets available to us we have a little over 2 million Class C networks now if we look at the third column we can get an idea of how big each network is in terms of how many hosts can live in that particular group so for a Class A that's your biggest one you can have the most hosts there in the formula there is 2 to the 24th because you have 3 octets dedicated to the hosts and that gives you almost 17 million hosts for each class a network and there are a total of 126 Class A networks so that's a lot of hosts not only for each network but then in total all the class A's if you look down to class B's it gets a little bit smaller because now you don't have as many octets available for the host portion only 2 this time so it's 2 to the 16th and that gives you about 65,000 hosts per Class B Network and there are 16,000 384 Class B networks and then finally the Class C is the smallest number because it only has one octet dedicated to it for hosts and there the total number is 254 this chart here is also something you'll need to commit to memory it comes up in the certification tracks so it's something you just have to commit I suggest memorizing the formulas that's probably the easiest way to go ok and that brings us to the end of this tutorial to summarize what we went over we know that there are three classes of networks and each Class A B and C has some unique characteristics to it now we can tell an IP belongs to a specific class because each class is ID if I buy a particular range in the first octet so again go back to those charts and memorize them and each class is unique in terms of the number of networks and the number of hosts available and that's because each class has a different formula in terms of how many octet Saar dedicated to the network portion and how many octet Saar dedicated to the host portion okay so that's everything you should know about classes of networks there's a fair amount of information but if you go through it a few times it'll start the stick and include this in in your your lessons of mandatory information that really you just need to commit to memory okay so that's it that is IP addressing and network classes thanks for watching

Channel: System Engineer

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Id: rJ8dK0lwet4

Length: 11min 43sec (703 seconds)

Published: Mon Apr 24 2017