Module 3:IP address, Subnetting, VLSM and Summarization

[Music] hi my name is todd lammle and welcome to module three of the CCNA fourteen module series this module is IP addressing subnetting variable length subnet masking and summarization just from the name of the module you can see that this module might be somewhat long at over an hour it's going to be so we're going to do this one in somewhat chunks where I'm going to say okay you're gonna take a break now you should take a break I'm also going to have some lab time in between different modules or distant different sections within this module just so you can break this up I'll also tell you to stop go back and go through this section again is this module although long and has a lot of information is very important so we must have this foundational knowledge to be able to move on to the other modules in this series so let's go ahead and take a look at IP addressing subnetting the LSM very linked subnet masking and summarization let's start with binary to decimal conversion and then we're going to do hexadecimal a decimal conversion we need to understand this is just foundational material again now we're working through Chapter three of the CCNA study guide if we look at a binary number it's going to be eight digits long each digit - haven't value from one 228 starting off the right moving left doubling value as we move left example 1 2 4 8 16 32 64 128 well it's gonna call these our block sizes and we'll get to that term in a minute if I have no bits on in a byte my value is 0 notice I have 4 bits on here and what I'm going to do is take where there's ones and I'm going to add up their value now it's really easy when up here I have the bit values so you don't always get this in life but in this case we have the bit values up here so we'll just add up a lot eight four two and one that's 12 two is 14 plus one equals 15 in this example we have 64 bits turned on the 16 that's 80 plus 4 is 84 85 now I always like to start with the largest numbers and then move to the right adding the smaller numbers but it really doesn't matter how you add them up that's just my ease of use let's take a look at another one 128 plus 2 is 130 plus 1 is 131 on this one it's 16 plus 4 is 22 now let's count up this law this last one and you're gonna see that these are also our subnet masks that we use and doesn't matter if we do in Class A Class B or Class C subnet masks always are the same they just move into different octet so that's the good news so once I teach you my method of subnetting in a certain art ad and we'll just start with Class C of course then you're gonna learn that this subnetting this method can easily be moved to any octet and the answers are always the same I'm gonna show you how easy this can be however I can't in Russia sure you can rest assured that you will go through this module more than once just for practice and as a matter of fact having this module is a really great tool because subnetting is kind of like going to the gym you can't be in shape by going to the gym once you have to go all the time so to be in shape with IP we need to practice all the time and this module is gonna be great to watch over and over and over again especially maybe if you can't sleep that's a joke anyways we've got the 128 bit on + the 64 bit is 192 so let's just add all these up so 128 is a subnet mask I have two bits on that's a subnet mask then and 128 64 is 192 if I turn three bits on 128 64 is 192 plus 32 is 224 128 + 64 is 192 plus 32 is 224 plus 16 is 240 240 plus 8 is two forty eight plus four is 250 two plus two is 254 plus one equals 255 now the numbers go for in an any octet go from zero to 255 that's 256 numbers now what I just read you was turning on a bit at a time from left to right without skipping bits that's actually how we get our subnet mask 128 192 - 24 - 42 48 to 52 to 54 and 255 that's all the mass you can have in any given octet let's go ahead and now and learn how to do hexadecimal to decimal conversion so if I take these same numbers this is called a byte because there's eight bits so what I want to do is break this up into nibbles and I mentioned the first module had you watch that I'm not sure that a nibble is 4 bits so here's one nibble and here's the second nibble so the numbers only go from 0 to 15 which is kind of nice so they can't get too big so it's really easy my decimal decimal I'm sorry hexadecimal conversion number here - decimal hexadecimal is 0 0 so my answer would be 0 0 now on this second one if we look at the second line my first nibble here is definitely a 0 there's no bits on but look at this 1 1 1 1 1 that's 8 and 4 is 12 plus 2 as 14 plus 1 is 15 in hexadecimal you can't use the numbers 10 11 12 13 14 15 as we only can use one bit zero or one so when we get to ten we're going to call that a 11 would be B 12 would be C 13 would be d 14 would be e and 15 is F so in this case let's take a look here again this answer in haxe would be 0 F now this one here is 0 1 0 1 again just starting to write in moving left 1 2 or 8 that's all it is and down here this is my second level 1 2 or 8 so both of these are 5 so that's a 55 and decimal isn't it hexadecimal d5 now how do you know that that is in hexadecimal and not being listed in decimal we're doing hex we're doing binary to hexadecimal conversion I'm sorry if I said that wrong early binary to hexadecimal conversion so if my hexadecimal number is 55 how do I know that's not decimal well the answer is because we put a zero acts in front so if it says 0x55 we know that's a hexadecimal number for the example before that 0 X 0 F was the second line here taking a look again 0 F 0 X 0 F is my hexadecimal 0 X 0 0 and on the third line 0x55 on the fourth line here 1 2 4 8 1 2 4 8 this looks like an 8 and a 3 1 & 2 is 3 so this is 0 X 83 0 X 83 and this one looks like the one bit on and 1 2 4 8 so that looks like 6 doesn't it 0 X 1 6 now just looking down here we can see all the bits are on the wean it really can do we have to add that up to 15 I guess we can 1 into 4 8 8 & 4 is 12 14 15 15 and 15 really is 0x let's take a look at one more example from binary to hexadecimal conversion so what is the decimal and hexadecimal equivalent of this well let's first add up the decimal for fun this is fun right 128 this is the 64 bit it is not on this 32 16 8 4 is not on the 2 and the 1 so there's a lot of bits on here as we can see so let's try to add these up Excel just wrote them down here 128 and 32 is what 160 plus 16 is 176 plus 8 is 180 4 plus 2 is 180 6 plus 1 equals 187 that's somewhat of a hard number if you don't write it down but nonetheless that's how it's done now to get our hexadecimal equivalent of a binary number we're gonna break this byte into two parts called a nibble so we just break this in half 1 0 1 1 and 1 0 1 1 8 Plus this is the 8 for the 2 and the 1 what's on the 8 the 2 and the 1 a plus 2 plus 1 so it's 10 1 so that equals 11 and 11 and a is 10 B is 11 so the answer is zero XB b isn't it now let's continue on with some binary and let's take a look and I've already kind of talked about this but let's just I'm just gonna ride it out again and we're gonna memorize this pattern so if we have these bits in a byte 0 through 8 my binary what's turned on my decimal equivalent if I have no bits on my byte value would be 0 if I have one bit on starting at the left and moving right and I can't skip bits because we're talking about subnet masks here they can't skip bits have one bit on seven bits off that gives me a mask of 128 if I have two bits on that's 128 plus 64 is 192 this gives me two bits on and six bits off so we need to remember this so you might want to go back over this on the screen many times if you have a mask of 128 that's one bit on in seven bits off you have a mask of 192 that's two bits on and six bits off so if I have three bits on in five bits off I have the 128 in the 64 is 192 plus 32 equals to 24 so if I have a two to four mask I have three bits on and five bits off if I have four bits on in four bits off I'm going to have a 240 mask 128 64 is 192 plus 32 is 224 plus 16 is 240 a 240 mask is four bits on and four bits off by a five bits on in three bits off I have a 248 mask a 248 masks five bits on and three bits off they might be saying to yourself what is he doing this sounds ridiculous is nothing like I've learned before is absolutely true I promise you though if you pay attention and you learn with me and you trust me I will get you to where we need to be but you just have to trust me for a few more screens and memorize what I'm telling you and then we will be able to submit in our heads it won't take long it'll be helpful if you read chapter 3 of my book but I'm gonna try to do that without even have to read that if you can help it anyways 5 bits on it's off is a 2:48 mask so and six bits on and two bits off is a 252 mask now if you're using Class C if you have a Class C address you can only use a mask from 0 to 250 - let's take a look like on a 254 mask you only have one host bit the ones being subnet bits the zeros be inhospitable suis have the less host bits we have so this might this is based on your network design and what you need more hosts or more subnets now in this case you have to have at least two host bits you'll be able to create a subnet mask you can't have one host bit or no host bits which if we look the 254 mask gives us one host bit the 285 is all subnet that's a so to go over this again the 1 to 0 mask if that's an acid for example 255 255 25 0 means we have no subnet bits on in the fourth octet if I have a 128 mask in the fourth octet 255 255 255 dot 128 that means I have 1 7 a bit in 7 host bits in the fourth octet if I have a 2 to 4 mask that means I have 3 bits on in the fourth octet in 5 host bits 3/7 of bits 5 host bits 240 means I have for subnet bits and 4 host bits 248 means I have 5 subnet bits and 3 host bits 252 means I have 6 subnet bits and two hosts bets again if we're doing this in the fourth octet we're done these are our masses take a look at this for a second our subnet masks are 0 means we don't have any sudden of bits 128 192 to 24 to 40 to 48 to 52 that's 1 2 3 4 5 6 we're doing classy something or something in the fourth octet we can only have 6 subnet masks so this means we can be successful because there's only 6 masks we have to remember you're going oh I've heard that before but I promise it's going to be true just hang in there if we have a 254 mass 7 subnet bits 0 host bits a 285 mask all subnet bits now let's go on with our techniques we've learned our masks and how many bits are on and off I back up and go over that until you have that down I promise you the rest of the modules will be easier if you can remember what I'm giving you right now let's talk about block sizes for a minute it is something I came up with a long time ago and actually determined in the early 90s how block sizes are used within subnet masks to create a group of hosts well once I learned about block sizes and how they were used it changed my whole career and is probably one of the reasons that I'm sitting here today I learned that block sizes can help us easily not only subnet or they can help us do summarization variable length subnet masking wildcard and asking for SPF configurations as well as access lists so block sizes are our friends okay so by learning block sizes and how they're used it will really help us to understand how we can easily subnet and how networks are easily logically put together so let's go ahead and memorize our block sizes for each subnet mask I think what's really important here is the screen before this understanding all your subnet masks how many bits are on and off so we know how many subnets and hosts that we have and if I also look at a subnet mask I know it's block size there's a couple things this is going to tell me first then if I look at a mask I know it's block size I know the actual subnet in that mask that I can use as well as the amount of hosts that are available per subnet that's some pretty good information let's take a look 2:56 and by the way we use the number 286 here because there's 256 numbers remember I said 0 to 255 in any octet that's 256 numbers we minus the subnet mask and we come up with the block size so 286 minus 128 because that's my mask these are my masks right comes up with the block size of 128 so what does that mean to me well starting at 0 that's always gonna be my first subnet right now 0 and I count in increments of that of that block size so if ever if I have a 128 mask and say 0 the next increment of 128 is 128 what's 128 plus 128 256 you actually want to count to 256 and I'll explain why in a minute so we're gonna say 0 128 256 256 cannot be a valid subnet so my subnets are 0 and 128 if that's the case how many hosts do I have per subnet well it isn't the answer isn't 128 but what I have to do is take the block size and just minus 2 so I say I have 2 subnets each with a hundred and 26 hosts now why do I minus 2 because there's a network address and there's a broadcast address that are used for each subnet those are not valid hosts in other words they cannot be assigned to host or router interfaces or printers or servers or anything like that so they're not valid for use and put on our hosts so we minus 2 from our block size that gives us the amount of hosts so if my block size is 128 I can count my subnets starting at 0 in increments of 1 28-0 128 256 count to 256 but don't use it as a subnet now I know the amount of hosts per subnet it's the block size minus 2 in this case two subnets each with 126 house ok hold on I know my 128 mask what do I know about it so far there's one bit on seven bits off the block size of 128 my subnets are 0 and 128 and I have 126 hosts per subnet I need you to remember this information and it is doable because if I'm doing it you can do it and I am NOT a genius ok the fact is the reason that I can do it because I go to the gem of IP every day that's all you have to do and you can remember this this isn't rocket science it's just memorization techniques let's memorize the next subnet mask okay we have the 192 mask and what do we know about it so far it's two bits on and six bits off well it's also a block size of 64 56 minus 192 is 64 so let's count our subnets 0 64 128 192 256 so that's 4 subnets each with what 62 hosts how do I know that because the box size is 64 so what do I know about my 192 mask well I know it's 2 bits on and 6 bits off with a block size of 64 the subnets are 0 64 128 192 each of those having 62 hosts each again you can do this just practice practice practice and by the way if you're studying for your CE sent or CCNA objectives you have to know it just like I'm saying it to you it is critical in your success let's take a look at the next one the 2:24 mask that's a block size of 32 please memorize your mask your block sizes the bits on and off okay so I'm just helping you do that right now the 224 mask is three bits on five bits off the block size of 32 so let's count our subnets starting 0 0 32 64 96 128 160 192 2 24:56 that looks like 8 subnets each with that's right 30 hosts now there's other ways to figure out how many subnets you have other than counting on your fingers but I'm just showing you a very simple way to do it what I want you to remember right now is if you see a 2 to 4 mask you know there's 3 bits on 5 bits off the block size of 32 8 subnets dirty house you have to be able to say it as I'm saying it right now not trying to be mean I'm just a messenger okay 240 mask block size of 16 so how many bits do we have on and off in a 240 mask it's 4 bits on and 4 bits off now I'm going to show you that by not counting our fingers how we can do this in the next slide but for right now I'm just going to know that that's 16 subnets how many hosts do I have per subnet well it's a block size of 16 so I have 14 hosts so here's what you're gonna remember about a 240 mask you forty masks or bits on or bits off a block size of 16 16 subnets or teen hosts now by the way it is critical that you can count by 16s and it is pretty hard to do I don't know if you could try this without me doing it I'm gonna do it here in a minute when we get to that section accounting by 16s is pretty critical for the CCNA objectives the 248 mask the block size of 8 so what do we know about the 248 mask well it's five bits on and three bits off and trust me that that's 32 subnets I'll show you how I got that in a minute I really don't want to count 32 sudden that's on my hands anyway so I have 32 subnets each with what six hosts that's right so what do we know about the 248 masks five bits on three bits off it's a block size of what eight there's 32 subnets each with six votes now the 252 mask six bits on two bits off lock size of for 64 subnets two hosts each Wow wooden will be used two hosts I mean that's pretty good right host router or something this is what we'd see on our win links wouldn't we router the router where they only use two house I'll show you that in a minute but a 252 mask when used in the fourth octet will only give you two hosts 64 subnets new house so a 252 mask six bits on two bits off block size of 464 subnets two house yeah 254 to 255 mask well there are block size of two and a block size of one I'm going to hold off on the rest of the memorization techniques for those until we get later on in the section what I want you to remember is the 0 obviously if there's a 0 there's no subnet subnet mask so it's one network it's a 128 mask we have one bit on seven bits off with a block size of 128 two subnets each with 126 hosts the next one is a 192 mask and what we need to remember about that is it's two bits on six bits off a block size of 64 or subnets 62 hosts each the next mask is a 224 mask Reeb it's on five bits off block size of 32 8 subnets 30 hosts each the next is a 240 mask or bits on four bits off block size of 16 16 subnets 14 hosts to 48 mask by bits on three bits off 32 subnets 6 house to 52 masks 6 bits on 2 bits off block sighs of for 60 to 64 subnets each with to house now let's go ahead and memorize and act our exponents and how we can figure out if we have two to the six how do they know that was 64 subnets and so on let's take a look at that so what we do is we use our exponents for the amount of subnets or hosts so we don't have to we can use the math in other words instead of just memorizing them obviously memorizing would be better but if we take a look at here we use our exponents to our powers of 2 2 to the 1 equals 2 so if I have one bit on it gives me two subnets for example r128 mask only had one bit on so we have two subnets if I have two bits on as are 192 masked us that gives me four subnets three bits on is our 224 mask has is 8 subnets or bid someone is our 240 masters gives us 16 subnets 5 bits on like our 248 mask gives me 32 subnets and 6 bits on as our 252 mask gives me 64 subnets so instead of counting on our fingers which we can easily do starting at 0 and counting through our block sizes we could use our exponents to quickly and efficiently figure out how many subnets and or hosts because we can use the same thing for the amount of oh so if I had a 192 mass that gives me 6 host bits that means I look I have an answer of 64 but we know we have 2 minus 2 gives me 62 hosts it's easier just to remember the 192 mask is a block size of 64 that always is going to give me 60 to host or subnet so it is unfortunate but part of our memorization techniques for IP subnetting or IP addressing is exponents and no you cannot use the calculator now in real life or in production networks we can use a calculator but we need to remember some certain aspects of of the mask and those are without being able to use a calculator we need to know the mass we do know how many bits are on and off the block size be able to count in that block size and how many subnets and hosts I get from each mask now remember in a class see it's not that hard there's only 6 subnets so if we just keep going over and over and over again everything I'm telling you you will get it and if you do have my book and are reading chapter 3 this really will fill in the black now so what we need to remember is two to the eighth equals 256 now why do I say 2 to the 8th 2 equals to 86 because it's right in the middle here kind of so if I remember to the 8th equals 256 2 to the 9th is going to be 512 why is that because it's double 256 so I just keep doubling it what's 512 and 512 1024 that would be 2 that to the 10th - to the 11th is let's take a look here 2048 2 to the 12th is 4096 to the 13th 8192 2 to the 14th is 16 384 2 to the 15 32 768 really all you need to remember to and trust me that's a lot isn't it so we're going to come back here and look and remember all of these and memorize them I hate to say you have to do it but you do and just if we just remember to the eighth this 286 we can cut it in half go to to the seventh is 128 or go to to the 9th which is 512 so just keep doubling it or cutting it in half either way that's a great memorization technique IP addressing is 32 bits long broken up into dotted decimal 8 bits each 8 bits equal a byte so we can see that we have 4 bytes now these are broken up into different classes of addresses that we can assign to host there's actually 5 classes but only 3 classes we can use to assign hosts with Class A says we can only use the first byte to define the networks in the last 3 bytes to define the host bits Class B says we use the first two bytes to define the network than the last 2 bytes to define the host bits for each Network class he says we have the first 3 bytes 24 bits to define the networks and only eight bits are 1 byte to define the amount of hosts on each network Class D is used for multi-class multi casting and Class E is used for scientific user just really not in use anymore anyways Class A we take a look here 8 bits on 24 bits off all the 24 bits off our host bits all the bits that are on our network bits Class B we have 16 bits for networks and 16 bits for host bits Class C 24 bits for networking and 8 bits for host so obviously these were made for different sized companies Class A made for a very large size company with lots of hosts and Class C used for lots of different companies with a small amount of hosts now how can we tell the difference between a Class A Class B or Class C Network well the difference is in the first couple bits of the first byte let's go ahead and take a look at that in a Class A the address range is say the range is 1 to 126 and how do we get that they say the first bit can never be turned on in a class 8 network so if we turn the first bit off and all the other 7 bits off our value is going to be 0 we leave the first bit off turn all the other 7 bits on we're going to get our range 0 through 127 now obviously we cannot use 0 as a network address nor 127 most of us already know that 127 is reserved for our loopback or diagnostic host it is unfortunate that reserved that whole class 8 range for the one 2017 or one host ID but nonetheless our range is 1 to 126 so why is this important understand anytime you see a host ID that's between the number 0 and 127 from 1 to 126 what that says is that we have three bytes for our host bits a lot of host bits so this will help us find where our host bits are and I'm going to explain to you why this is so important in the next slide but in this case let's take a look here again if I have a Class B the first bits always has to be on but the second bit can never be turned on that means if we take the other seven seven six bits excuse me six bits off and turn them all off those six bits and turn them all on that gives us a range of 128 through 191 so anytime we see an address range that starts with 128 through 191 we know the last two bytes are our host bits for a Class C the first bit must always be turned on second bit must always be turned on but the third bit can never be turned on so if we take our range and turn all the other host bits off our byte turn all the other host bits on again our range is 192 through 223 so that's our Class C range whenever we see an address range from 192 to 223 we know that only the fourth byte is used for addressing of hosts those are our host bits so taking a look at how we can use this if I see that I have a 10 here that's a Class A which means the next three bytes are my host bits so how do I get my network address and broadcast address and why do I care the network address is all host bits off the broadcast addresses all host bits on so why do I care about this because I want to get my valid host range my valid host range is all the numbers between the network address and the broadcast address not including the network caps and broadcast headers which is why when we got our block size we - to the network caption broadcast address so for this example we have a 10 which means the next three bytes our host addresses by default and then so we'll turn them all off to get our network address we'll turn them all on to get our broadcast address or are valid hosts were always the numbers between the network address and the broadcast address in this case 10 0 0 1 through 10 255 255 255 is our valid host range that's a lot of hosts by the way we really can't do that in production but nonetheless it's an example of how or why we would - - and how to get your network address and broadcast address they get a look at the next example 170 - 1600 it's a 172 so that gives us a Class B so that means only the last two bytes are our host addresses so we would turn off the last two bytes make them both 0 and that would be our network address to get our broadcast address for this network address we would turn all the host bits on so it would be 170 216 255 dot 255 our valid host would be the numbers in between 0 1 through 255 dot 255 now remember obviously these are the default masks which we'll talk about in the next screen but it's still important to understand that when we find a subnet or network we turn all the host bits off to get our network address turn all the bits on to get our broadcast address again that's why we - - from our block size to get our network out to get our amount of hosts 192 is a Class C this means we're only using the fourth octet - for our host bits it means we only can use a fourth octet for our host bits so we would turn that all off it's a zero turn all the host bits on to get our broadcast address and our valid hosts are the numbers in which one through 254 so again it's important to remember that when we have a network address get the network address we turn all the host bits off you get the broadcast address return all the host bits on the valid host for that subnet are the numbers in between the network address and the broadcast address now let's take a look at what it's like to use the default mask to use non default subnet mask and really what are our default masks okay in this example we don't have we have a Class B which means the last two bytes are our host bits and if we had a default mask we would have all our host bits in the last two octets will be 172 16 0 1 0 2 and so on all the way up to 2d 5.2 54 you want to figure out how many hosts that is please do 2 to the 16 that's really what that answer is isn't it now if we really wanted to do this right we would take this class b network address we're using and what we're going to do is borrow bits from the host bits and create subnets or sub networks so in this case you can see we're using the third octet to create subnets in this case it's 10 20 30 40 each router interface is a different subnet different logical network different broadcast domain isn't that almost the same thing but only on the land is this a broadcast domain not on the way and this is not considered a broadcast domain but it is a subnet or logical network isn't it so on our lands though these are broadcast domains so what we're going to do in order to create subnets is we don't take bits away from the network addresses or anything like that we take bits away from the host bits we add subnet bits into the hosts section taking away host bits so the more subnets we have the less hosts per subnet we're going to get now our default mass for a is 2 2 5 0 0 0 where these zeros are where our default host bits are so you can see why the last three octet Tsar host bits in Class A in Class B it's 255 255 dot 0 0 and so only the last two are caps by default are used for host bits Class C 255.255.255.0 the fourth octet is the only bite that is host bits now if I wanted to subnet I would have to in the CAHSEE right here start right here the leftmost bit that's the 128-bit and move right not skipping bits so my mass would be 128 192 224 to 42 48 to 52 I can't do anything more than that because the 252 mask is 6 bits on 2 bits off and I must have at least 2 bits for hosts so those are my masks in class II starting with 0 mean and I have 1 network with 254 hosts and if I have a 128 mask gives me 1 bit on and 7 bits off doesn't it and someone this is why we want to memorize this these are the only 6 masks that you can have so how do I determine which masks that I want to use do I want to just come up and say I'm going to use the 240 mask because it's right in the middle 4 bits on and 4 bits off which by the way gives me 16 subnets each with 14 hosts so first off we want to count the number of subnets in the network and remember to think about growth then we count the number of hosts in each subnet remember to think about growth as well now we can think about this as subnets or a lot of times we might be doing virtual LANs and I know that's in a later module but the fact is is a lot of times we just have switches today which allows us to create virtual LANs so once we determine how many subnets slash virtual LANs we're going to need we're going to determine how many hosts we have in each subnet or virtual LAN and again we just do this by counting the number of subnets and Counting the amount of hosts and determining if there's going to be growth or not and then we can base our mask on the amount of subnets and hosts that we need now once we determine which masts we're going to use we need to ask yourself two questions how many subnets does this mask provide and doesn't meet my business requirements if it doesn't meet my business requirements I have to go back and find a different mask how many hosts per subnet does it meet my business requirements so do I have enough subnets do I have enough hosts is this right is this my business requirements if not add more subnet bits or take them away based on your business requirements and you need to keep doing this until you get the right mask for your network so once I have my mask and I determine the amount of subnets and hosts and I determine them ask is right there's four the questions I have to ask before I can implement this what are the subnets what are the valid hosts for each subnet and what are the broadcast addresses well really this is the easy part once I determine my mask I think that's the hardest part doing network design is really what this is so for example if I have the 192 mask I know of a block size of 64 so what are my subnets 0 64 128 192 256 those are my four subnets okay well here comes the fun part after everything we've got to we're finally going to have some fun right if I'm in the zero subnet the next 7 it is 64 what's the number right before 6463 well if I'm in the zero subnet the broadcast address for the serial subnet is 63 my valid host then would be the numbers between 0 and 63 because zeros my network 63 is my broadcast address my valid hosts one through 62 so that's how we do this now I know you're going oh my gosh that that's incredible I I don't think I could ever do this no you can you can because we're gonna go through a lot of practice and we're gonna do this over and over and over again we're going to do it for each and every mask so let's start with the 128 mask if I have a 128 mask we know my first subnet is 0 always starting at 0 the next mask is 128 the next increment of 128 is 256 so starting at 0 128 is my next subnet what's the number right before 128 127 so for the zero subnet 127 is my broadcast address because 128 is the next subnet so my valid host then must be one to 126 the next of its 128 the next increment of 128 is 256 what's the number right before 256 255 if we do this right we start at 0 and in that 255 so my next 7 is 128 my broadcast address is 255 my valid hosts are the numbers in between 128 and 285 those are my subnet and broadcast address 129 to 254 let's go back to the 192 mask again it has two bits on six bits off with a block size of 64 my subnets are 0 64 128 192 256 if I'm in the zero subnet the next seven at 64 so my broadcast address is 63 valid hosts are the numbers in between the network and broadcast address in this case one through 62 the next subnet is 64 seven after that is 128 you always have to know what the next increment is so you get your block size or broadcast address 64 128 the number right before 128 is 127 64 is my network address 127 is my broadcast address valid host 65 to 126 next seven it is 128 the subnet or after that is 192 number right for that is 191 so if I'm in the 128 subnet my broadcast address is 191 my valid hosts are 129 through 190 my very last subnet is 192 the next increment of 64 is 256 the number right before 286 is 255 we did in that 255 we started a 0 and ended at 255 so we must have done something right so my last 7 is 192 the broadcast address is 255 valid hosts are 193 through 254 we have the 224 mask it's 3 bits on in 5 bits off with the block size of 32 my subnets are 0 32 64 96 128 160 192 into 24 not going to go 320 these I'll just do a couple if I'm in the 0 subnet the next 7 is 32 so 0 is my subnet my broadcast address then would be 31 valid host 1 to 30 if I'm in the 220 I'm sorry if I'm in the 32 subnet the next subnet 64 so my broadcast address is 63 valid host 33 through 62 so so on and so on and so on you do the same thing for every single mask every single block size the next mask is a 240 mask these are my block sizes of 16 now I have to tell you you have to build count in 16s because we have to be able to submit anywhere within the 240 masks so let's start at 0 count all my subnets all up to 256 we might even do it backwards okay you ready 0 16 32 48 64 80 96 112 128 144 160 176 192 - 24 - 42:56 backwards 256 242 24 208 192 176 160 144 128 112 96 80 60 448 32 16 0 I think I did that all without skipping if not we need to do it again and what you need to do is do this over and over and over again and why do you have to do it backwards well if we're something in our head and we're way up in the to 40 masks we have to be able to know what something it is without starting at zero we don't have time to start at zero and count all the way through so let's do this section over and over and over again till we know our sixteenth forward and backwards I can't tell you how important it is to your success okay so if I'm in the zero subnet the next subnet is 16 so that makes the broadcast address of the zero subnet 15 so if I start at zero my broadcast addresses if I'm sorry 15 my valid hosts are 1 through 14 if I'm in the 16 subnet the next subnet is 32 I'm in the 16 subnet my broadcast address then would be 31 valid host 17 through 30 and so on the next subnet mask is 248 my bits on and three bits off with a block size of 8 0 8 16 24 and so on you can count all the way to AIDS through 256 if you'd like zero subnet the next subnet is 8 and makes my broadcast 7 valid host 1 through 6 I mean the eighth subnet the next subnet is 16 broadcast address of the eighth seventh then B 15 valid host nine through 14 and so on can you see that the method has done the same we're just counting in different block sizes that's all it is okay just one more okay 252 mask 6 bits on 2 bits off block size of 4 let's count them all zero four eight twelve I'm kidding anyways zero subnet the next seven it's four so my broadcast address must be three valid host one and two next subnet for something after that eight broadcast for the for subnet seven valid host five and six and so on and so on and so on so I'll done in the same way now in increments of your block size this is why it's so important you could look at and ask it no it's block size as you know two things you know the subnets once you know the subnets you know the broadcast address of your subnets it's always the number right before the next subnet and you know how many hosts are are per subnet cuz it's always the block size minus two now basically on this screen it's just showing you exactly what I went through it's just how to get the six answers but I just went through that all in my head and I know you can do this too if you need to just go backwards and do it over and over and over again but I have a memorization technique coming up that's really going to help you now before I do that though I want to talk about something called classless Internet domain routing it's a way to hand out IP addresses without saying the mask 255 twenty-five twenty-five to fifty to we can just say slash thirty in other words how many bits are turned on out of 32 so we're gonna find out that classless Internet domain routing his other name for a variable length subnet masking and so on later in this section but nonetheless when we give out a cider address or slash notation I'll call it we have to determine what the mask is and then everything else we know about that mask so anyway so if we look at a slash eight we know that said 255 0 0 0 because what that saying is how many bits are turned on out of 32 / 8 means there's only the first byte because that's a bit let's take a look at this so the eight bits on 255 0 0 0 16 u 255 255 0 0 to 2 bytes on slash 24 8 16 24 now as you can see I've got all these Class C maths here because that's what we're studying right now so we know the first three bytes is 8 16 24 that's not gonna change for the rest of our masks so we always start at 24 bits are on right here 8 16 24 now we just have to determine how many bits are turned on with these last Matt's in the last octet a 1:28 mask has how many bits turned on I hope you said one so that would make this 24 plus one is a / 25 24 and 192 mask is 2 bits on exists of / 26 to 24 mask has 3 bits on makes its of / 27 to 40 masks or bits on / 28 to 48 mask / 29 and lastly a to 52 mask as a / 30 and by the way as last 30 masks is the largest master you can have regardless of your class of address as you always must have 2 bits on now IP 7 and 0 remember how I we said we always started 0 0 16 32 48 and so on we started at 0 0 32 64 0 64 128 0 8 16 and so high we started 0 the reason that is is this inside a router you must have this command on IP subnet - 0 now if that command is not turned on you can't start at 0 for example if we were in the 240 mask and started instead of starting at 0 16 32 we'd started 16 32 48 and we couldn't use the last mask of 240 as well so what this does is make it so we can't use the first in the last subnet so we wouldn't be able to we'd have to - too far our subnets and that's a waste waste of space so IP subnet - 0 is turned on by default starting with 1212 Oh make sure it's turned on the CCNA objectives are based on the fact that do you start at 0 or don't you please look for this command it's a troubleshooting spot that you need to be aware of if that command is not in there you can't start at 0 okay one last section in this part of the module and that is when we see a or this is what I call the what do you know section and this is going to help you bring everything together that we've learned so far it is a great part and I encourage you to go over this over and over and over again till you can say it just like I am I'm gonna have it on the screen and I encourage you to go backwards and backwards over and over and over again and you know what you need to do between now and the time you take your exam if that's what you're trying to do do this every single day multiple times if possible so you if we see a slash notation that's what we need to know we need to be able to turn it into a mask how many bits the block size how many subnets in-house and we're going to memorize this and so everything we've learned so far comes down to this one section so for example what do I know or what do you know about a slash 25 and of course we always talk about a Class C at this point but we will see when we get to Class B and Class A that we get to use the same information again over and over over again it does not change so it's important to memorize this a slash 25 is a 128 mask one bit on seven bits off block size of 128 two subnets 126 house please say it with me it's important that you say this out loud now as a good instructor you always make sure that students can learn by either writing it down typing it in or saying it out loud so I encourage you to say this out loud with me you ready a slash 25 is a 128 mask one bit on seven bits off lock size of 128 two subnets 126 hosts now this can't be that hard because I have it on the screen for you so the key is can you say this without the screen let's try it you have a slash 25 what do you know it's a 128 mask one bit on seven bits off block size of 128 two subnets 126 house now that wasn't so bad was it let's take a look at the next mask which would be a slash 26 what do you know about a slash 26 say 192 mask 2 bits on 6 bits off lock sizes 64 for subnet 62 host say it out loud with me slash 26 192 mask 2 bits on 6 bits off block size of 64 for subnets 62 hosts now let's do it without looking at the screen are you ready what do you know about a slash 26 it's a 192 mask 2 bits on 6 bits off lock size of 64 or subnets 62 house I know this can be difficult but just keep doing it over and over and over again until you can get this down just like I'm saying it right now take a look at the next one which is a so 27 and by the way we don't have too many more so hang in there if you have a slash 27 what do you know say 2 to 4 masks 3 bits on 5 bits off block size of 32 8 subnets 30 hosts say it out loud with me because we're about to do it without looking at the screen you if you have a slash 27 what do you know it's a 2 to 4 mask 3 bits on 5 bits off block size of 32 8 subnets there anyhow ok here we go last 27 what do you know 2 to 4 mask 3 bits on by bit soft lock size of 32 8 subnets 30 house that's not so bad is it let's take a look at a slash 20 8/28 is a 240 mask or bits on four bit soft lock size of 16 16 7 it's 14 hosts at say it out loud slash 28 what do you know 240 masks 4 bits on 4 bits off block size of 16 16 7 it's 14 house here we go without the screen what do you know about the slash 28 it's a 240 mask 4 bits on orbits off block size of 16 16 subnets 14 house there's only two more hang in there / 29 what do you know say it out loud 248 mask 5 bits on 3 bits off lock size of 8 32 subnets 6 hosts here we go / 29 what do you know 248 mask by bits on 3 bits off lock size of 8 32 subnets 6 hosts we only have one more and to me it's easiest one if you have a / 30 what do you know it's a 2 5 2 masks 6 bits on 2 bits off lock size of 464 subnets to most out loud here we go / 30 what do you know 2 5 2 masks 6 bits on 2 bits off lock size of 464 subnets to hosts here we go if you have a / 30 what do you know it's a - 5 - mask 6 bits on 2 bits off lock size of 464 7 minutes to your house now let's take everything we've learned so far and put it to use and figure out how we're going to use it because we've learned a lot of information and again I encourage you to start from the beginning and go all the way up to this point and make sure that you have this all memorized but once you have this done we're gonna say really that's great Todd we learned all this memorization techniques what do we do with it well let me show you now we don't have to do all this math one of the things that I'm trying to get you away from is having to do math I know that in a lot of classes they have you do binary math and all this other anding and norine and that's just crazy you do not have time to do that for your CCNA objectives we need to get right to the point so although I'm showing the math on the screen it's only because I want you to know I'm not making this up and the answers do make sense let's take a look at the first one this is a slash what not a slash 24 its 816 24/25 isn't it 192 means it's a Class C so that means I have one bit on seven bits off it's a block size of 128 two subnets each with 126 house this really was the what Tino section but all I did was write it out really I encourage you just to go back to the what Tino section and memorize this forget about writing out the mouth what's the point there is no point memorize the answers that's all you need now here's how you use it I have two subnets we know that the first seven is zero because I have IP subnet zero on the next seven that's 128 and then increment of 128 after that is 256 if I'm in the first subnet which is zero the next seven it's 128 the number right before 128 is 127 so my network address is zero my broadcast address is 127 my valid hosts are one through 126 the next sublet is 128 the next increment of 120 is 256 so the number right before that is 255 you we started at zero and we did in debt 255 that's nice subnet 128 broadcast 285 valid host 129 through 254 now I call the section very easy subnetting because basically I'm just showing you the what do you know section written out we're gonna go to EZ something here in a couple minutes and then you're gonna see that we don't need to write out the math that's ridiculous again I'm only showing it to you seeking so I can prove to you that I'm not making this up but please just memorize the what T no section and we're now what do I do with these two subnets well this is the zero subnet so again I'd connect him to a router subnet 1 7 a 2 or they can of course be virtual LANs so on this router I look at this router I go to the router prompt which we'll learn about in module 4 show IP route that's to see my routing table now one of the things that this is going to show me is this C stands for directly connected so if I type in my network number correctly in other words I have to put the router as a valid host and remember what's if I'm in the 10 0 the next 7 is 10 128 or I'm sorry if I'm in the 0 7 at the next 7 it's 128 so my broadcast house would be 127 my valid host 1 to 126 I made the router here dot 1 it really didn't make any difference what I named the router the only reason we need to know what it is so we can set all the how their host to their default gateway address to the correct default gateway address then I just start hopefully using probably DHCP 2.3.4 and so on all the way up to 126 but I can see that this network 10 0 x and v a-- Ethernet 0 now how does the router know this because if you assign an IP address to an interface with the mask and then enable the D interface the router hauling that can go out there and say oh you're in the 0 subnet oh this interface is in the 128 7 it it can do it slightly faster than we can now easy subbing 192 168 10 0 this is a slash 1 8 16 24 and 2 bits to slash 26 to bits on 6 bits off block sizes 64 or 7/8 each with 62 hosts but for a 192 mask my subnets are 0 64 128 192 256 right in the zero subnet the next 7 is 64 the 7 8 right before that or the number right before 64 is 63 that's my broadcast address valid host 1 through 62 the next subnet 64 then the subnet after that is 128 then we write for 128 is 127 which makes my valid host for the 64 7 at 65 to 126 and so on it's all done the same way so what do I do with these 4 subnets good question I'm going to apply them to either router interface or VLANs or however mining use them so this would be my zeros and sixty-four subnet 128 subnet now if I had serial links which are not shown in this picture that would be a separate subnet every single link on a router must be its own subnet so if I did a show IP route I'd see my directly connected networks off this router and I still have another network another subnet left over for growth let's look at the next subnet this is a slash twenty seven it's a two to four mask by bits on three bits off block size of 32 eight seven it's 30 host and I actually do show all the subnets here 0 32 64 96 128 160 192 224 course to go to 256 please be able to count all your block sizes of 128 64 32 16 8 and force be able to share be sure to be able to count in all those block sizes so practice practice practice finding the zero subnet the next subnets 32 the number of right before that is 31 which makes my valid host 1 through 30 I'm in the 32 subnet the next 7 at 64 number right before that is 63 which makes my valid host 33 262 and again as we'll see here I can apply these two router interfaces notice my way in link this is a landling point-to-point between I could t1 for example this is in the 64 subnet now we can see there's a lot of wasted address space in here and this is what vlsm will fix for us but we don't even using the 0 subnet don't have to start at 0 somewhere actually I do not I can use any of those subnets anywhere any part of the internet work take a look at the next subnet this is a what slash 28 8 16 24 and 4 bits is 28 which gives me 4 bits on 4 bits off block size of 16 16 7 is 14 host let's count by 16s again shall we 0 16 32 48 64 80 96 112 128 144 160 176 192 208 to twenty four to forty to fifty six if I'm going over this again and ten you must memorize it it must be important so if I was you I would really really understand my block size of 16 if I'm in the zero subnet and the Knicks lock size of 16 yeah the next increment of 16 is 16 mm right for 16 is 15 my fellow hosts are 1 through 14 16 7 at the next valid 7 it is 32 number right before 32 is 30 100 17 to 30 32 sudden at the next 7 is 48 broadcast 4733 to 46 and so on the next subnet 72 48 mask worried this this one and one more weird that's easy something then we're gonna get to the very easy 70 and so hang in there 1 I 2 and 68 10 zeros Class C this is a / 29 my friends 248 mask is is 3 bits on in 5 bits off with a block size of 832 7 and 6 house and count by your 8 0 8 16 24 32 40 48 and so on if I'm in the 0 subnet the next 17 is 8 the number right before that is 7 so my valid hosts are only 1 through 6 6 host right I'm in the 8th subnet the next 7 8 is 16 so then right before that is 15 valid host 9 through 14 Nick's seven eight is sixteen seven after that is 24 number right before 24 is 23 which makes my valid host 17 to 22 let's take a look at our last mask that is the 250 - r / 30 it's 6 bits on 2 bits off block size of for 64 subnets to house down by 4 0 4 8 12 16 20 24 and so on if you're in the 0 subnet the next 7 is 4 and we read before 4 is 3 about hoster than 1 and 2 again to house if I'm in the for subnet the next subnet is 8 the number right before 8 is 7 so my valid hosts 4 5 & 6 I'm in the 8th 7 at the next 7 is 12 member right for that is 11 so my valid hosts are only 9 and 10 now let's take a look at when we'd use these and again I already mentioned that if I have a win link I have to have a separate subnet and if I had like a flash 28 or / 29 there could be a lot of wasted host bits there so in this case this would work great on LAN links wouldn't a slash 30 would work great here Unwin point-to-point links it wouldn't work so great here if I'd have a host router I'm sure Cisco would love that if you had a host router right doesn't even have to have a router port for every host but typically we'd see a slash 30 you're able to do this this is called classless routing variable-length subnet mask is how I would use slash dirty and our wind links and that's going to be later on in this module okay enough of this easy subbing stuff it's time to get to the very easy subnetting now you have to take the what do you know section and apply it after you do this we're gonna have a written lab you're gonna get a little break before you finish the rest of the module let's take a look so last twenty six what do we know we have to know what the mask is they have number one if you don't know what a slash 26 is you'll never be a lay into the question / 26 is a take a look 255 255 255 dot 192 that's right so a 192 is a block size of 64 now I have an IP address here of 68 if I have a block size of 64 what 7 is this host in you might easily be able to say all that must be in the 64 7 well what we have to do is count by from 0 count Landon convinced of that block size until we passed the host address why do we need to pass it we need to get to the next subnet so we know what our broadcast adverse is 0 64 128 the address were looking for 68 so what is in the 64 subnet the next 7 it's 128 so the broadcast headers of the 64 subnet is 127 valid host 65 to 126 so the 68 or this host address here when I to in 68 m dot 68 is in the 64 subnet the broadcast address is 127 a valid hosts are 65 through 126 let's do another easy one you might be going this isn't so easy I promise you it is if you go if you know the what - you know section and you go over this again and again and again this is really easy and you need to go over this again and again and again until you can do it like I'm saying it this is foundational material that you must know a slash 27 is a what mask you can't answer this question if you don't know what mask it is you can't answer the question 255 dot 255 dot 255 dot 2 - 4 is net 2 - 4 mask in the fourth octet is a block size of 32 the address we're looking at here is 65 so we're going to count by 32s tell we passed 65 you ready 0:32 6496 so if it's a 65 we're in the 64 subnet the next subnet is 96 - my broadcast address is 95 ballad hoes 65 through 94 take a look at the next one which is a slash 28 once the slash 28 again if you don't know what they are if you're struggling with this please memorize the slash notation to mask and having how you can take a size notation into a mask and again hopefully you're reading my chapter 3 if not some book that explains this where you can see this printed out 192 168 10.30 8/28 that's a 240 mask in the fourth octet with a block size of 16 so we're going to count by 16s until we pass 38 ready 0 16 32 48 inning ding so we're in the 32 subnet the next 7 is 48 - my broadcast address must be 47 valid hosts are what 33 through 46 are we subduing this in our head you bet we are so all we need to know to subnet in our head is what block sizes my friends I already told you block sizes are your friends you need them for the rest of this module for the beginning of this module for all the modules please understand your block sizes take a slash notation turn into a mask and know what block size it is you can do that you can answer any question any subnet question whether it's a B or C and I'm going to show you that in the rest of this module so we know this is in the 32 sub take a look at this again broadcast address 47 because the next subnet is 48 now let's take a look at the last one I'm sorry this slash twenty-nine we got two more so last twenty-nine is a what mask you have to be able to answer that question 255.255.255.0 that's correct that's a block size of 8 in the fourth octet the number we're trying to get is 26 it's a host ID of 26 what 7 it isn't in what's the broadcast address 0 a 16 24 32 so I'm in the 24 subnet the next 7 is 32 so my broadcast address is 31 my valid host 25 to 30 okay one more and then you get a break slash 30 is a what mask 255 dot 255 dot 255 dot 255 that is a block size of four in the fourth octet and the number we're looking for is 13 so let's just count by force till we get there starting at zero IP subnet zero is turned on zero for a 1216 I mean the 12 subnet the broadcast address is 15 valid host 13 14 I encourage you to start at the beginning of this module and come all the way through here and do it over and over and again until you can do it like I'm doing it okay let's open our books if you purchase the books with the video series or you have another set of labs let's do a written lab 3.1 if not go ahead I really recommend taking a break or doing it all over again doing this whole section all over again before you go on to the next sections in this module

Channel: Lekit Mendon

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Id: PXbFfPV3CCM

Length: 64min 51sec (3891 seconds)

Published: Fri Feb 03 2017