Subnetting Explained Step by Step & Subnetting Chart

you welcome to my second tutorial on subnetting chart table if you prepare for a Cisco exam like CCNA or if you're an IT student and need some better understanding of subnetting this video is for you but you must know the basics of networking protocols especially IP version 4 so you must know what an IP addresses and you must know its structure for example what an octet is if you don't please learn those basics first and then come back here to watch this video the first introductory video explained briefly how to increase the network portion changing the subnet mask or in other words what is the relationship between the subnet mask and the network and house portions this video shows you how to draw a new subnet in chart table it's easy to do just follow me and soon you'll become a subnet master so let's start okay we're going to draw the chart table first thing we're going to do is to write down the decimal values for each of the bits in the octa and so first value is 128 second is 64 third one is 32 for 2016 then 8 for two and one once we have all the decimal values for the bits within the octet we write down our border line you remember our imaginary border line between the network portion and the house portion this is it once we have it we write down the subnet mask inside the notation for Class C which is 24 and now remember borrowing the bits from the octet all right now you write down 25 because we borrow one bit here we write 26 here because we borrow 2 bits and so on 27 28 29 30 31 and 32 and now we were getting to the point what is the subnet mask value in dotted decimal notation 4/25 it's 128 4 / 26 okay it's not 64 it's 128 plus 64 4 / 27 is 128 plus 64 plus 32 so to make the things easier I'm going to write down another row of values these values will be psalms of the following values from the octet bits and so in first place we have 128 in the second one you have 192 because 128 plus 64 is 192 in the third place 192 plus 32 is 2 2 4 2 2 4 + 16 240 240 plus 8 is 248 two forty eight plus four is two fifty two plus two to fifty four plus one is two fifty five all right now we have all the values written down for class see how to use or how to read the table now if you have example of / 25 subnet mask that means that if you look up here you read 128 so it becomes remember we're working with Class C that means this is the last octet so we would have 255 dot 255 dot 255 remember this is our border line and now 128 if you had for example 29 in side row notation what it is in dotted decimal notation simply look up here what it is it's 248 so right down in the last octet as we work in with Class C and we have 24 bits already assigned to that class so first three octaves would still have 255 255 dot to buy 5 in our different example if you had for example given that the subnet mask in dotted decimal notation a subnet mask of 255 255 255 dot to 48 and you want to find out what it is in Sider notation you simply look down and you find out that it is slash 29 all right now let's complete our table for Class B and for Class A in Class B remember the subnet mask was 16 so adding one more bit would be 17 adding one more bit would be 18 and so on so we can simply and easily fill out our table 23 and 24 for for all the classes class a the subnet mask was slash eight so the next one adding one bit is slash nine adding another one is slash 10 and so on slash 11 12 13 14 15 and + 16 and now an example from Class B remember Class B uses 16 bits for the network portion so if you are borrowing bits from the host portion you now you're jumping from the second octet to the third octet so the numbers will be working with appear in this in the third octet not in the fourth octet like in Class C and so for example let's take slash 18 what it is in dotted decimal notation definitely we use two octaves so 255 dot 255 dot the third octet which will read 192 and put it into third octet and then we have 0 another example / 22 / 22 gives us 255 dot 255 now we're jumping from the second doctor to the third octet we have looking up to 5/2 so we're writing down to 5/2 and now 0 we can work this out in other direction too for example if you are given with a subnet mask - sorry 255.255.255.0 that Class B uses 16 bits which are 2 octaves when you add some more bits you're jumping to the third octet so you need to read this row this line in order to get values from the third octet so what it is then in third octet for two to four it / 19 and last short example from class a if your subnet mask is 255.255.255.0 14 our value in this line is 12 so / 12 and we know that 12 is between 8 and 16 so it must be the second octet the same in other direction for example / 13 what it is / 13 I'm looking here I found it looking up its 248 in which octet in second octet so it's 2 55.2 48.0 to 0 ok you might think that we have completed our subnetting chart table but i'm going to show you something more actually something that makes this table really useful really really useful okay I have my table cleaned up so you can see only the numbers only the values and the question is how big are those portions those smaller subnets where do they start where do they end because once one subnet ends the next one right after it starts and so on and so on this chart table shows you all those values alright let's take an example a network 192 168 dots tandel 0 and let's say / 26 subnet mask we know that subnet zero will be at 192 168 or 10.0 how big is this subnet where it ends where the next one starts ok let's look at the table we have / 26 here now we're looking up up at the top row 64 number 64 tells us that the next network next next subnet will start at 1 9 2 1 6 8 or 10 dot 64 where the next one starts again we need to add 64 so 192 one six eight dot 10.1 28 because 64 + 64 this 64 gives us 128 sometimes the values from the top row are called steps or magical numbers why because for example here we have 64 which is a step between first subnet and step between the next subnet I'll stab it in another one and so on let's take another example 1 9 2 1 6 8 touch 10.0 different subnet mask let's see 20 okay we're looking for 20 in the table once we found it we look in the same column but the top row we find number 16 and the 16 now becomes the step between the subnets using this subnet mask so we need to add 16 another 16 for another network another 16 for another subnet and so on so remember you're working within one octet here these values don't change only these values change with for the subnet mask so 0 16 next 32 next 48 so these are subnet addresses subnet values that use slash 20 subnet mask and here's the final result our subnetting chart tape nice and clean I hope you find it useful and easy to use if you like my tutorials please leave comments and hit the like button and thank you for watching my video

Channel: Jacek Majda

Views: 480,053

Keywords: subnetting, subnet, chart, charting, table, easy, explained, step by step, create, make, use, draw, tutorial, how to, educational, ccna, cisco, networking, ip, classfull, classless, bonus

Id: Gt0RQX3QCO8

Length: 14min 57sec (897 seconds)

Published: Sat Mar 24 2012