Lecture - Practical VLSM

all right so in lab today what we're going to be doing is we're going to be going over some of the LSM stuff I want to make sure that we have a pretty good understanding before you guys start your exam next week right so there's exam on Wednesday of next week tonight I will unlock the Cisco assessment for chapter 7 you guys will have until Thursday usually give you guys three days to do the Cisco assessment so you'll have today tomorrow or Thursday to accomplish this assessment one thing I want you to keep in mind is I just posted a new data link layer PowerPoint overview like I told you in days before when I make those powerpoints I connect them to every learning objective for that chapter so they're a good overview to start with study for the exam and folks when you're watching these videos if you do choose to watch them do not watch them on your lazy boy you should be watching them on a computer station in front of a desk or on top of a desk with plenty of paper alongside you and write your notes that way I've learned to try to consolidate these to make them smaller in timeframe but when you do that it means that I'm using other ways to relay the information like visual aids animation highlights verbal communications and even text so it might take you 18 minutes to watch that video if you just sat back and watched it from your lazy boy but if you're writing notes and you're being actively involved pause rewind pause stop right okay they're your notes I don't know how you guys learn some people learn by doing other people learn by writing other people learn by watching there's all different types of learning styles out there all I'm telling you guys is when you watch those PowerPoint overviews be a little bit more aggressive than just sitting back eating popcorn the shows on entertaining okay I mean it's just all knowledge being dumped in 18 minutes for Chapter seven it takes me a week to read that chapter it takes me even longer to write those powerpoints so put some effort into it that's the way you're going to memorize the material or know the material I should say what I'm going to be doing in lab today is we're going to go over these vlsm exercises we're going to be doing four of them I modified the last one just to give you a challenge to prepare you for the lab that's due tomorrow it is posted on blackboard check it out Stu tomorrow is really no different than last week's lab so if you guys saved last week's lab you can just open it up and just modify the addressing the challenge is in the vlsm okay so there's two purposes today get you ready for next week and then get you ready for the labs to do tomorrow here's the other thing I'm going to give you guys a heads up I will do the first one to show you again what vlsm is all about the second problem I'll be doing with you the third problem you guys would be doing it for me and then the fourth problem you guys will be doing on your own okay well I wouldn't say on your own but more like on your own with me okay any questions before we begin everybody has this all right with the first problem that we're given we have a network address or I should say a block of IP addresses that begin at two twenty ten 10.0 and notice I said it begins at two twenty ten ten zero where does it end can I determine that I'm given this bit of information right here which we call the prefix the prefix is another way of writing a subnet mask this prefix is telling me that slash 24 so the very first 24 bits are going to be used to represent what the network part right it also tells me the first 24 bits I can't touch remember you're buying a block of addresses they begin at dot 0 now I could say dot 0 now because that's last 24 it's telling me that after the twenty-fourth bit all the other bits are the host right now instead of me going out and buying another block of how many well if this last 24 is telling me 24 bits of the network therefore 8 bits are 4 they host because an IP address is 32 bits long and if I'm saying reserved 24 of those bits then I have 8 bits to play around with do I need all 256 addresses for this network do I need it for this network over here so what's the need of going out there and buying 2 blocks of addresses or 256 wide when I can buy one and split it in half if you will why split it in half maybe split it so it's better appropriate or better proportioned to the actual networks I have everybody's clear about that just laying down the groundwork why am i doing that well let's say a packet comes in this router has a choice to make it's either going to go right or it's going to go left if it goes right it's going to end up on this network if it goes left it's going to end up on that network you're clear about that what does the router use to decide which path to send a packet on these are all exam questions so I'm building this time as a review for next week's exam chapter five stuff what does the router use technically there's two three things not the MAC address it's going to be the IP address this is all logical all right MAC addresses are just physical addresses that are signed for local networks all right this is beyond a local network because deciding what network to put it on right so what I care about is the network address and this is the only time the network address is ever used does that make sense so this is switches that use MAC addresses correct correct now we got a choice if I'm using the network address to determine what pathway to put this on there these two interfaces cannot have the same what same IP address more importantly the same network address I mean I'm making a statement if the network address equals this then pass it down this block or this line if the network address equals that then pass it down here if both will make this equal the same thing my router is going to be confused I mean this is like coming into right before you get into Corning you see a road with the sign on it says go left Corning go right Corning I guess I can go either way to get there correct but both of those networks aren't going to contain the same information the same resources so I need to identify these groups of hosts with a network address and I need to identify these groups of hosts with a network address so I told you a network address logically groups host together they're used by routers to determine the path that a package should travel there's that theory with about maybe eight or ten points on the next exam given that information which network should I start working with what's subnet should I start assigning addresses first start with the largest then you work your way to the smallest all right so I have 60 hosts what is my network address going to be for those 60 hosts this is my first network correct so why not start at the beginning what is the beginning of our block our beginning is 220 dot ten dot 10.0 so the first question is what is the network address for the subnet next question what is the network prefix now remember the subnet mask handles two things it helps the router determine what the network address is and what's the second thing that the subnet mask is used for the width of our networks so so how do i Turman that my network prefix my subnet mask I asked myself to raised to what power is going to be able to accommodate all 60 host to raise the six now math class is born because they lack the units what is that six what does that six represent I need my units on there there are host bits visually what does that look like now remember folks I'm contained what I mean by being contained is that I am locked into this last octet how do I know I'm locked into that last octet because I started off with this last 24 right so I'm going to map out those off those bits net octet one two three four five six seven eight eight bits in the last octet now you're telling me that I need to do what with these six host bits am i borrowing them or am i leaving them alone I'm leaving them alone what six bits are those are they the first six bits or the last six bits why are they the last six bits so one two three four five six we've draw my line here this is me visually understanding what's going on here why is it the last and not the first that's exactly what I want to hear all the network businesses stay together a subnet is a network remember an IP address consists of only two parts a network address and a host part right or network portion and a host portion you want to try to keep all the network portions together so when I write out my subnet mask I have all consecutive ones you remember what the ones do by the way are these eight ones one two three four five six cheating one two three four five six seven and I got a bad habit two four six and then how many more I draw out eight ones here one two three four five six seven eight these are the 24 ones that represent this but my new prefix is going to be what where did I get the 26 from I borrowed those two ones okay if I have those two ones being borrowed what would my subnet mask be if I had to configure these devices remember the computer sees all ones as the bit above it is part of the network address and then if it's all zeros the bit above those or the host portion right that's the way they determine this so what is the subnet mask if I have 26 from my prefix I'll do the hard part 255 dot 255 dot 255 dot what 192 because I have a 128 here and I have a 64 there okay what is my broadcast address for this network see that's all I care about network address subnet mask broadcast address why do I care about the network address so I can configure my router properly why do I care about my subnet mask so I know how to calculate my network address so the routers can pass the package correctly second I know what the width of my network is why do I care about my broadcast address because remember I can't assign the broadcast address just like I can't assign the network address the broadcast address is used to send messages to everybody on the same local area network write by calculating the broadcast address I know what my usable range is my usable range is going to be between the network address and a broadcast address we call them usable because I'm allowed to use them to assign different hosts and address the other thing I like doing by calculating the broadcast address is that I know the next number after this broadcast address becomes the next network's address if I want to keep things packed together everybody's clear about that what is the broadcast address in binary for this network first of all what is the network address all zeros in the host portion and I started off with a dot zero to begin with right so my network address is eight zeros in the fourth octet because that's what I assigned this network correct so I put in eight zeros two of them are red because I can't touch those now that their subnet it what's the definition of a broadcast address then when it comes to binary all ones where and the host portion all right what goes over here above these two red zeros they're the same they can't be touch they'd better be the same right because devices on the same logical network have the same network address correct where's the network address to the left of that line so those bits better be the same now here's a shortcut instead of adding 32 16 8 4 2 & 1 close what's the number right before 6463 if I put a 1 right here and put all zeroes that's the number right after this correct I always like to use the old odometer example in a car remember those old black dials in a car please guys don't tell me I'm dating myself if you don't know just google it do a google search and image search and type in classic odometer and you will see what I'm talking about here now just use your imagination these these little dials that roll around right they're written in decimal so they got 0 to 9 correct this is your ones column and that might go all the way up to a thousand hundred thousand whatever depends on how old car how old's your car it is what dial is going to roll the most the one on the far right right now in binary all we have is two choices 1 or 0 correct so if I'm at the end of my dial this is going to roll back to a when your car reads 9 9 9 9 across it's odometer the one on the far right it's going to roll back to a and when that rose to a 0 what happens to the next one that rolls right well we can't say goes to ones I don't know what it is but that will roll correct so this is out of one at the very end of the dial correct it's going to roll back to a zero that means it goes to the next one what's this I'm going to roll too and then is going to go the next one this was what is this one I'm going to roll to we're going to keep on rolling zeros until what this one rolls to a one you notice where the one rolls to right here across the line the next network address how do I know it's a network address because I have a one here then all zeros afterward right what's the number right before 63 sorry 6463 so when you guys see all ones here just go to the next column and minus one from it that a nice shortcut because oh I thought you said sixty-four I'm sorry you know I'm getting old and deaf and blind but I also have to compete with this fan so if you're confident with your answer say it loud that's why you guys hear me yelling all the time because I'm deaf and dumb and I have this fan right above me so you know I do apologize for making you feel like you're an idiot but you're actually right so if you did say 63 good so this address broadcast address is going to be - 2010 . m dot 63 now I do that because guess what I get to do next I go to the next largest network correct which is only this one this is the last one and what's the network address going to be for this subnet I'll do the hard part 220 . 10.10 dot you want them to be consecutive correct now remember you're looking back at that binary pattern and that binary pattern looks like this can't touch those so far one two three four five six seven oh you network address is when you have all zeros correct we said this is 64 what if I didn't want to do 64 what if I didn't want them to be consecutive I wanted to leave room to grow for this network exactly right here and then what if I want to skip ahead again what would the next binary pattern be do you see the red digits and how they're counting subnet zero was this one with all zeros right here subnet one is a zero followed by one subnet two is a one followed by zero subnet three is a one followed by one and that's it I can only handle four subnets I get to pick and choose where I want them to be at if I want this last network to be right here then my network address have been 192 because remember in the host it's all zeros does that make sense folks as long as these bits change I'm in a different network if they stay the same I'm in the same network so I'll leave it like this what's my subnet mask going to be because that's the next question once I know my network address is I got to ask myself what is the subnet mask how do I answer that to raised to what power is going to be able to accommodate 28 host 2 raise to 5 all right so what are those 5 bits represent visually what's that those slide bits represent the host portion these are host bits so that means I got to go from the right to the left 1 2 3 4 5 draw my new line what happens to that black zero now yeah this area now is my red zone do you see how I just created another area that I can create a subnet with and what is my prefix going to be well I have all ones then all zeros after the line correct we clear about that I like to put the subnet mask on top of everything because it really dictates where my boundaries are this is my network address dot 64 but what is my prefix 27 because I have these three ones plus the original 24 ones correct what would the subnet mask be if I had to write it out or configure a computer two-twenty that's 255 255 dot 255 dot 2 24 because I have a one night 128 plus 64 plus 32 okay what's my broadcast address kind of bear and binary what do I do broadcast address all ones in the house part what's all ones well what's this now converted back into decimal 95 let's say yes I heard you correctly this time 95 yeah that's the way it always works for students they're not sure they're always quiet and I don't make fun of you too much when you guys are wrong do I I mean you are on YouTube so she'll be the world's biggest idiot but that's no different for me than every day so you guys should fit right in pretty clear you guys want to see a more elaborate problem not that you have a choice but I like to give you that illusion of having a choice all right this is where I go around and pick on you guys suddenly you out once again say it loud so I can hear you because I'm deaf and dumb and it's only gonna get harder as I get older whoops I want it oh that was a nasty there we go can you guys see that in the back the bottom area okay good I'm given a block of one ninety two dot one sixty eight dot 16.0 slash 24 let's start with the first student Evan upfront um which network you and start with the biggest one which yet this one right here the one twenty correct all right so what's the network address going to be for the 120 yeah it's going to be one ninety two dot one sixty eight dot 16.0 because I'm starting with the largest one why don't I begin at my block correct first there could be you know this is just I know it's like me saying you guys should always put your underwear drawer on the top dresser you know your top drawer in your dresser it's just the way we do it it doesn't have to be this way it's the way you arrange it but I always suggest is starting that way because otherwise you're just going to forget that you began that way but two reaches their own as long as you allocate the right space and you have enough bits for the subnets I don't see anything wrong with it I mean some people want to make this the wain area so they might have started that way I'm the other way I always like to start with the largest work whether way down to smallest it makes it really easier to calculate easier to manage because if it's easy to calculate it's easy for you guys do it in the field but it's completely arbitrary what hasn't changes the formula or the method all zeros all once right so next question I asked myself after I calculate the network address is what's the width of my network do I need all 256 hosts for this network I just need seven so I'm just going to map this out for the people that are watching us at home 1 2 3 4 5 6 7 8 and so 2 raised to what power as I was informed with 7 to raise the 7 is going to be enough to accommodate that so those are 7 host bits since their host bits I start at the right one two three four five six seven and I draw my line there okay Evan now that I drew that line I'll help me out writing out the subnet mask what would I wear I put the ones and then what happens after the line so what is the prefix then slash twenty five because we have this one right here and we're adding it back to the original prefix of twenty four what is the network address ah let's do a in what's the network edge ah you already told me the network address there but what is it in binary yes a minor it's all zeros okay now knowing that detail the host portion satisfies the definition of a network address tell me what the broadcast address would be all ones where now what do I put in the network portion because I want to make sure that belongs to the same network so therefore the broadcast address is going to be one ninety two dot one sixty eight dot 16.1 127 because if I were to put a one right here it'd be 128 so the number right before 128 is 127 Oh Ryan what's the next Network we want to work with 60 not like we have a choice right largest to smallest what's the network address going to be for 60 very good because you're deciding to make that consecutive in fact you have a choice here because you only have one bit for the subnet right so after zeros you're going to get once so let's look at this in binary I have 1 2 3 4 5 6 7 8 you're Tommy that my network address is going to be a 1 here and then all zeros now I know this to be a subnet bits I'm going to change the color to be red and now the next question is going to become what is the subnet mask for this network hence the word very because we're changing it each network accordingly so Ryan Oh what is the prefix how would I calculate that I asked myself that question too raised to what power is going to be able to accommodate 60 host to raise the sex those are six host bits right because to raise the sex gives me 64 64 is more than enough to accommodate 60 host addresses by the way I might try to trick you up on the exam you should add 2 to these why are we adding 2 to these numbers we gotta count 1 for the network and 1 for the broadcast all right so where I can count me what I'm going to do with those 6 host bits could I simply take 32 minus 6 at this point and get the network prefix I mean after all I'm telling you if there are host bits lay off of that don't touch them correct if an IP address has a total of 32 bits then subtract the bit you can't touch which are 6 32 minus 6 gives me a network prefix of slash 26 right visually that's one two three four five six draw the line here that means that zero can represent subnets more subnets as I'm going to make it red I'm also going to put my subnet mask above this all right Brian what do you think the network sorry what do you think the broadcast address is going to be for this network tell me in binary yet 191 works for me let's find out maybe I could be wrong but let's see tell me in binary one zero in here because they need to still be part of the same network so they have the same logical network address then all ones in the host well 128 plus 64 would give me 192 minus one would give me this bit pattern so that tells me at the broadcast address is one ninety two dot one sixty eight dot 16.1 91 alright Brian what's the next network you're going to work with what's the network address so I put one ninety two dot one sixty eight dot 16.1 ninety-two because that's the next address after that network right after the broadcast address of that network and what's the prefix going to be let me draw it out one two three four five six seven eight and we said that the original network address is going to be a 1 there and it's your show we asked ourselves to raised to what power is going to accommodate 20 hosts so to raise to what's going to accommodate 20 else to raise to 5 so what's the prefix knowing that slash 27 because 32 minus 5 is 27 visually it looks like this 1 2 3 4 5 draw the line this becomes a 0 here and then my subnet mask is going to be like that all right with that being said what's the broadcast address for this network Brett because you told me to put all one's here for the broadcast address and that's just one right before the 2:24 correct very good Oh Bret let's do this win right here what do you make the network address for this win all right we're going to do this in binary but save yourself some time on next week's exam remember this is going to be about 40 points of your exam there's a lot of math problems involved in fact I believe next week's exam I think the multiple choice questions on blackboard but then this part is a handout okay because people like doing math on paper which I don't blame you so here we are we have a dot 24 but I'm in a win with a serial connection what have we learned about point-to-point connections how many total host addresses are going to be in a point-to-point network for you should automatically look at that and say slash 30 right however let's play the good student and do our work I'm in the fourth octet one two three four five six seven eight eight bits are in an octet I have a slash 30 that tells me well I'm going to point two point four hosts to raised to what power is going to be able to accommodate four hosts you guys are going to tell me to one to draw the line right there 32 minus 2 is 30 my subnet mask is this all one's then all zeros my network address is as follows a 128 a 64 a 32 all zeros and my broadcast address is going to be what Brett one ninety two dot one sixty eight dot 16.2 27 and binary that looks like that write a 1 1 1 0 0 0 then a 1 1 okay Michael what's the next network address going to be one ninety two dot one sixty eight dot 16.2 twenty eight prefix last thirty good broadcast address first usable address you're 29 and that's what I would sign maybe this interface right here maybe I'll make that 1.2 29 and the last usable address which would go in by default right here right what would I make the subnet mask for those interfaces 255 dot 255 dot 255 dot 255 so good guys don't be afraid to writing out those in fact I give out graph paper for you guys on the exam make a little bit easier to keep track of these bits all right on to the next one why don't you guys get started as I erase my board how many students I have here today can you guys count off so I know six how many networks I have in this topology how many networks do I have a nest apology I've huh and there's six of you guys yeah and we'll say hmm six house I'll do this one ah Michael do the 55 Brent do the 26 Brian do the 2012 Ryan do the 6 and because you guys set up front you're my favorite students you guys can do the winds ok I notice you guys are going to be working sort of at a sink I've been teaching guys how to do this in order correct so you guys could do them all or you can follow a shortcut I don't care I'm going to start with the 255 and so I believe Michael you're doing that I'll ask you the question and you'll give me all like the network address the subnet masks in the broadcast right I label them so you guys were next to each other so you might want to talk to each other let's see how that works out all right so you got it you're done Michael hi Brett then Brian and Ryan and then the guys at front you guys do in the winter Ian how about this wind right here yep and Evan how about this one right here and I'll do this one right there I'm not sure if this address block has enough I believe it does is I'm adding things up in my head but we'll find out I don't like to do the same thing over and over it gives me something different to talk about all right so Michael let's kick off the class I'll do the hard one for you it was one ninety two dot one sixty eight dot one dot zero right because we're starting with the largest one and we're signing it now what's the prefix for this this last twenty six is that what you wrote and the reason why we solve that is we said one two three four five six seven eight bits to raise to 6 is going to be able to accommodate my Twitter my 55 host so I go one two three four five six and then I see that I have two red ones over here plus the original 24 ones gives me this last 26 my network address is all zeros in the host portion plus all zeros in the subnet part because I'm starting with a zero in the fourth octet knowing that I can answer the broadcast address broadcast address is going to be still at the same parts right here because they need to be part of the same logical network however I put all ones and the host portion so Michael you would tell me it's one ninety two dot one sixty eight dot one dot one sixty three very good right knowing that you would tell me the network address for your network is and you would tell me that your subnet mask or your network prefix is going to be what because you said to raise to5 is going to be enough to accommodate 26 hosts 32 minus 5 gives you 27 right now for me to calculate the broadcast address I'm going to go back to my tried but true method of 1 2 3 4 5 host bits then 1 2 3 subnet bits you said 64 so I have a 0 here a 1 there a 0 here and my broadcast address would be all ones correct all ones is basically going to tell me what what do you have for your broadcast address so one ninety two dot one sixty eight dot one dot 95 all right it goes 64 plus 32 it give me 96 minus one now that you have that information Brian your network address is going to be what one ninety two dot one sixty eight dot 1.96 and your prefix is going to be what its last twenty eight because you said to raise to four is going to be enough to accommodate 12 hosts because 2 raise to 4 16 32 minus 4 gives me 28 for myself netmask very good ah going back to the tried but true we have 1 2 3 4 5 6 7 8 1 2 3 4 / binary subnet mask is all ones here then all zeros there right and your network address is 96 so that's a 1 here and a 1 there and a 0 there and since I'm asking for the broadcast address I want all one's right there being that I have all ones right there right what did you get for your broadcast address 192 dot 168 dot one dot 111 Ryan you are over here yeah host six correct what's the network address for this host one ninety two dot one sixty eight dot one dot 112 because that's the next number after the broadcast address to the previous subnet okay what is the prefix Brian Ryan's I rhyme so you told me that to raise two three is going to be enough to accommodate six host and you're right because to raise the three is eight and so 32 minus three gives me twenty nine all right so that tells me that I have one two three bits over there and then I have one two three four five bits there I have a network address of a 0 here a 1 here a 1 there and also a 1 there and a 0 there is that correct in binary we have 64 plus 32 is 96 plus 16 gives me 112 my subnet mask and binary is going to look like this and the broadcast address is going to look like this in binary which tells me that I have a broadcast address of one ninety two dot one sixty eight dot one dot Ryan that was all you would you have a for a broadcast address 1:19 very good all right and what's the network address one ninety two dot one sixty eight dot one dot one twenty and that should be a no-brainer right point to point so slash what okay I'll go with that what's the broadcast address alright I'm still good with that I Evan network address for this one did you hear that authority and his voice he made sure I heard that correctly all right so it's one ninety two dot one sixty eight dot one dot one twenty four and your broadcast address is going to be very good by the way folks we never even got to my other subnet I still stayed right here in this column after I'm done with this I'll go to the 128 so I'll go back to my original first block if you will so graphically I look like I split this in half and I have 0 to 127 and then I have 128 to 255 that work that we just did was all of this right the first subnet sent half of this original box so this was some Net Zero the next one said half of that original box it's that old math riddle I go from where I'm at here and every time I go to walk it's always going to be half the distance of where I started with right so I'm here I'm going to the wall let's say this is five feet so I go two and a half feet right and if every time I cut the distance in half will I ever reach that wall because now it'll be out a foot and a quarter away from the wall now I'll be 3/4 away from the wall and then I'll be 3/8 and so on right if I keep on cutting it I'll never reach the end of that wall I'll never touch that wall but what happens to the distance it gets cut in half correct so I'm keep on cutting these boxes in half which allows me to redress them so here I am I take this box which was 64 then 32 than a 32 and I cut that in half again and now I made this one subnet 2 and I took that 16 and I cut that up and to 8 and I made this one subnet 3 and then I took that box and I cut that up into two parts of force and I utilized that whole very first original block leaving 128 more addresses to play around with this is my network maybe I would have called up and said look I need a slash 28 work sorry misspoke a slash 25 let's say we're cutting this in half yes last 25 should be half the cost correct you guys ready for a challenge any questions want to make sure you guys feel comfortable with this before we move on I modified the next one because I thought that one was just too easy for you guys last octet of the so now is always one higher than broadcast demands that now it could just be yeah because we're doing everything consecutive in order so I've started with like 60 then I went down to 28 then it went down to 12 then I went down to 6 so the networks are even in order by their size naturally they would you know maybe I'll have two of them that are 60 and then another one that's 16 and then that'll throw that off yep depend on the mathematical form and not the patterns because in this example it really opens up the doors because it's not about oh I see this being moved to the left by one bit nope all right please guys update it yeah it's not on your paper first of all was on your paper was a 195 dot 109 dot something dot 0 slash 24 is that correct and then the host rather shallow so I want you guys to make it 500 you got the right one and I breathe rent you have the right one but for everybody else that has yesterday's I was looking for a challenge to give you guys so here it is all right do I have a brave soul out there that wants to start this off first the easy ones the first one right we're going to start with the network with 500 hosts okay what's network address for this host so I have 195 dot 109 0.0 however what does my prefix become hmm maybe all right if I put in binary so I can see it what am I going to put in binary what octet Sam I going to translate back into binary what's that one the third and the fourth one why am i doing the third and the fourth yeah do you see how this last 22 and that's telling me that I have ten bits that I can play around with right because IP address 32 in size 32 minus 22 gives me 10 but an octet is only how many bits long 8 so that means I bleed 2 over into the other octet correct so I'm going to map out all 8 bits are all 16 1 2 3 4 5 6 7 8 the dots just a separator you can ignore it when you're doing problems like this 9 10 11 12 13 14 15 16 you see when I started counting I started with 1 and ended up at 16 I get reset the counter as I went to the new octet okay according to this problem I have 10 host bits I'm allowed to play around with 8 plus these two of my host bits I cannot touch those bits to the left of that line so I'm actually splitting an octet up to what we were working with we always start with a whole octet well being that this address had a zero here good about that a 0 in the third octet I have to put that part in now the question becomes is what is my new subnet mask or my prefix 2 raised to what power is going to accommodate 500 hosts well 2 raise to 8 is 256 right so 2 raise to 9 gives me 512 addresses so that tells me I need to leave that whole octet alone plus this additional bit right there correct now I'm going to write it out the way a computer sees it and that is all ones up to the line correct and then what's after the line all zeros I have Oh maybe sometimes is better say I have nine zeros 32 minus nine gives me as Brian pointed out earlier that's the last 23 okay the network address is when I have all zeroes in the host part correct this is my host part where these zeroes come from from the original problem correct this blue zero should actually be converted to a red zero and these blue zeros should be black as in hands off do not touch because nothing's going to change them the red can change as well as the blue definition of a broadcast address is what now the network and the broadcast address have to stay on the same logical network so they better have the first bits together right but a broadcast address is defined by all what in what all ones in the host which tells me that my broadcast address is 195 dot 109 dot what what does the third octet look like back in decimal now I got to put these things back together that's the third octet what does that look like in decimal I have a one in the ones place correct so dot one dot what I got to take these ones and put it back in that fourth octet which gives me what our ones is 255 interesting what's the next Network we're going to work with the 201 right the next largest network what is the network address for the 201 195 dot 109 dot one dot 256 now because you can't go up to 256 right so what's it going to be Brian 195 dot 109 dot 2.0 how did you figure that out let's look back at this guy's remember the odometer example it gave you back at the beginning of the class if it reads off like all one's and I'm just going to drive one more mile because what's not what we were doing take the broadcast address add one to it correct that should be the next Network address so when I add one to this this is going to roll to a zero this will roll to a zero this will roll to a zero it's just trickling all the way down through this rules to a zero well guess what happens to that red zero as it should happen that rolls to one this is the next network address if it's the next network address the next red bit should change where is that one located it's in the twos place hence taking those bits and putting them back into decimal I get 195 dealt 109 2.0 now it's all downhill from here what's the subnet mask where the network prefix going to be so last 24 - raised to what power is going to be able to accommodate 200 while to raise to 8 gives me 256 32 minus 8 gives me a / 24 that tells me I need to steal one more bit from there that blue zero now gets converted back to a red 0 to represent subnet and my subnet mask is going to be all ones then all zeros correct and my broadcast address is going to be what oops yeah that was right broadcast address contains what in the host part all once they need to be part of the same network so the network address was a zero followed by a one correct I can't change these by the way I should have made those blue ones and now it's election day so I got to be patriotic so here we go all once there's your red white and blue which tells me that my network address is going to be 195 dot 109 dot two dots all ones in the last octet gives you 255 right all right what's the next Network address so I'm going to be over here on this host what's the next network address going to be for that a 195 dot 109 I had to change it up a bit dot what everybody see that just roll these all the way over this rolls to one I got two red ones in the set sorry the third octet and give me one 95.1 Oh 9.30 what's the prefix going to be you need 100 host nice 25 so you're telling me that I have to move the red line over one more I move the red line over one more by the way I gotta convert this to three these become this is my subnet mask 25 ones right and this one so when you're looking at this this is the network address is the subnet mask this is the broadcast address correct change the ones that are supposed to be coordinate correct so all zeros and the host portion gives me the network address which should also have all zeros from the subnet mask all ones in the host portion should be the broadcast address the broadcast address in this particular network is 195 dot 109 dot three dot wake up computer what because if I were to put and here's where my decimal places are not decimal but the octet placeholders so I put a 1 right in there I get a 128 so the number for 128 gives me 127 what's the network address for this guy 195 dot 109 dot 3.1 28 what's the prefix - raised to what power is going to be able to accommodate 40 hosts to raise the sex 32 minus 6 gives me this last 26 right broadcast address should be 195 dot 109 dot 3 dot 191 do the binary if you're not sure I'm just saying that if my network address is 64 128 and the size of my network is 64 128 plus 64 gives me 192 which becomes the next network address so the network the broadcast address is the address right before the next network address or the last address of a block what's the prefix for this one last 27 because to raise to 5 gives me 30 to host 30 to minus 5 gives me 27 now don't get them mixed up I'm not taking 30 to host it's 32 bits of an IP address minus 5 host bits it gives me 27 Network bits broadcast address should be 195 dot 109 dot 3 dot o 32 plus 192 so - 23 so what you guys got - one for all right let's start here for the network address 195 dot 109 dot 3.2 24/36 last 34 all my wins 195 dot 109 dot 3.2 27 195 dot 109 dot 3.2 28 for the network address broadcast address is going to be 195 dot 109 dot three dot oh let's see 231 by the way if you guys are watching this at home I probably should have told you to pause it calculate it then hit play to see what the answer is my apologies it's too late now but in the future if you start seeing me some answers getting randomly thrown up on the screen hit pause that's the nice thing about watching me on youtube you have control you can fast-forward me you can rewind me dot 232 next available address and that's going to end out 195 dot 109 dot 3.2 35 you how's it coming along guys a lot better okay so guys have 15 minutes to work on the lab the lab is due tomorrow night at midnight feel like wow all sudden folks it's the same lab you did last week the only difference is they changed the IP address that's it you know how to do that because this problem is the spitting image of that lab problem that you guys have lab study guide will post today it'll be sorry the exam study guide we posted today it is due by Friday Cisco assessment will be unlocked you guys will have until Thursday to accomplish this what else you guys need to know start reading chapter 11 tomorrow in class we'll be going into the iOS stuff all right you guys take care I'll see you tomorrow

Channel: Nicholas Andre

Views: 62,226

Keywords: Cisco VLSM Chapter 06

Id: 0xVlgKU_2zA

Length: 67min 21sec (4041 seconds)

Published: Wed Nov 07 2012