IP Subnetting from CIDR Notations

hello this is Joshua butcher we're going to look a little bit at subnetting from a cellular notation now this video will assume you least have an idea what an IP address is and what a network ID is and a broadcast ID and stuff like this but it will assume basically that maybe you've been studying subnetting but having kind of a hard time being able to get good answers or really wrapping your head around it there are many approaches to looking at this so hopefully this approach will help you as just one of the many different options you can look at to see understand this first things first we're going to look at I have an IP address here of 192 168 60 55 with a Sider notation of slash 20 what I need to be able to figure out is the network ID in the broadcast ID you in order to figure those out I need to understand what that Sider notation of slash 20 even means that represents how many bits are turned on within my subnet so what will help me every time I do this I first create myself a simple little chart I'm going to go ahead and make myself a chart right now and you don't have to use any graphical tools to do this but I use a chart here just because it's easy enough on here but I just write this on any piece of paper or anything I'm working with to make this kind of work out and then make my letters bigger right go and basically I start off from here and go to left 1 2 and it doubles its number up to 128 4 8 16 32 64 and 128 this isn't necessary to write this down but it's just going to help my mind as I try to wrap my head around what in the world is going on so let me get back to the cider notation first of all what does this even mean so when we're talking about a subnet mask usually you might be used to seeing two five five two five five dots something on those lines let's see what those really look like if I did 20 bits turned on let me go ahead and start that doing them in 8-bit rotations 1 2 3 4 5 6 7 8 . 1 2 3 4 5 6 7 8 . that's 16 current turned on that would be equivalent to slash 16 17 18 19 20 then 1 2 3 4 and all the rest from that point on will be zeros so this is equivalent of all the ones turned on as the equivalent of turning all these on and adding them together that would equal 255 so a subnet for this particular IP range will be 255 255 dot whatever this would be that would be these four bits all turned on which is these numbers all combined 128 192 plus 32 is 224 plus 16 is 240 so that'll be 2 40.0 that's what the subnet really works out to I don't need to translate that to make sense of this I'm just doing that so I can wrap my head around what I'm talking about well it's helpful though is really looking at this here now I can attempt to translate every single one of these in the binary but that is totally unnecessary what I need to do is translate just what particular one into binary really makes sense of this so I'm going to go here and I'm going to specify which one that matters in this point these are all on these are all these are all off so the third octet is my focus let me highlight over here third octet that's my focus since I know that's my focus I already know some information about the other fields these are all turned on so I know it's going 192 168 this as well 192 one six eight these will be consistent with every single number possible in the range the third row here is what I'm really trying to figure out and if these are all turned off that would be zero and but if they were all turned on that would be 255 so I don't need to figure out now it's just these two simple values to figure that out I need to translate this number here into a binary value and map it to this so I'm just going to go ahead and put in some fuel or fillers here and we won't do anything it recognizes here so we'll do X's 1 2 3 4 5 6 7 8 . 1 2 3 4 5 6 7 8 . and I just want to move this so I can see what I'm talking about here there we go so I want to turn this now into binary I'm looking at converting the number 60 all I really do is look at this chart here can I take 128 out of 60 no can I take 64 out of 60 no can I take 32 out of 60 yes that leaves me with 28 can I pull 16 out of 28 yes so that leaves me with 12 can I pull 8 out of 12 yes can I pull four remaining that would be 4 and the rest remaining would be zeros then dot and then it doesn't even matter again because I don't care about any of those other values right now these are the ones that need a map to so this is when the computer sees this and the computer sees this it determines the next row here of exactly what the IP address would be or that particular number let me just scan up here and this does this with something called a logic table basically it'll take the two values and if they're both equal true you don't make it true so if they're both 1 that'll make it 1 it might help to think of this almost a multiplication 0 plus 1 0 times 1 is 0 0 times 0 1 times 1 is 1 1 0 0 0 0 here we have this number identified all you need to do now is really translate this number and this will give me my network ID so this number is not that bit not that bad but these two bids turned on those two bits combined equals 48 that is my network ID pretty good to go so far now I just need to figure out what would be the next possible network ID in the list because whatever the next one is the number right before it would be the broadcast ID so the next possible one I have to figure out what that would be this is determined by looking at something called the magic number this is the last bit that's turned on whatever that is is the increments and how many they go up by so in this case the fourth one so I got one two three four they go up in increments of sixteen so 48 plus sixteen minus 1 will equal my broadcast ID if I didn't do the minus one it would be another network ID for the next possible range all I need to do it to 48 plus sixteen 48 plus 16 is 64 minus one would be 63 that's my network ID that's my broadcast ID now for the actual range I can use it's very easy at this point so 192 168 48.1 I can't assign that computer a dot 0 address through 192 168 60 3.25 4 because I can assign a computer a dot 5255 address this is my answer this is how it came about it hopefully this is starting to make sense let's look at another example or two so we can make sure we wrap our heads around this properly in this next example we're going to look at finding the network ID the broadcast ID and the usable IP addresses that seem to go in common here with 172 1085 60 with a slash 22 Sider notation once again to help myself out I'm going to go and make my quick little chart just my own brain I'll make a little eight chart we are oops it moved over really far I'll put it right here insert table eight and I'll just bring this up 1 2 4 8 16 32 64 128 now I need to figure out which octet do I want to focus on because I don't feel like translating all of these in the binary which one is it well anything really you can tell right away being it's between 16 and 24 it's going to be the third octet but I'm gonna go ahead and work this out anyway 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 so that's 16 17 18 19 20 21 22 that leaves me with 0 0 and 0 0 0 0 0 0 0 0 now I got this figured out what this means here of course if I won the actually know what that number was I could add all those together 1 2 3 4 5 I could add these guys together here the 6 and actually see what that / 22 means I don't wanna do that right now all I do know right away is it's going to identify my magic number pretty quick now I just need to figure out so I know I'm dealing with a third octet it's all I really care about let me go and highlight that the third octet which means some of the information I'm able to fill in already I got one night I got one seven two loops 10:01 seven to ten to fifty five I just need to figure out what these values are now in order to do that I'll need to find this number and then add the magic number to it subtract one and that'll be this so I'm going to find this first 85 so I need to translate 85 into binary let me do it over here dot can I pull 128 Eddie 85 no can I pull 64 at 85 yes and I just have to slowly start doing the math for this leaves me with 21 can I pull 32 out of there no can I pull 16 out of 21 yes so 16 from 21 is 5 can I pull 8 out of 5 no can I pull 4 out of 5 yes no yes that's what this turns out to be that is my basement what I need to do now is do the process of ending determine what's left 0 1 0 1 0 1 0 0 those are the ones that line up I just need to figure out with us from the chart so 64 let me code highlight this 64 plus 16 plus 4 and whatever number that comes out to be is this number here which would be 84 now I need to know the next ringings that comes in remember these work this last little bit here turned on is what's called the magic number that's one two three four five six one two three four five six intervals in four so if I add four to 84 that would be the next possible network ID in the list the one before that must be the broadcast ID so that be 88 minus 1 would be 87 now I have my broadcast address this now I can work out the rest 1 7 to 10 80 4.1 through 1 7 to 10 80 7.2 54 now I start working my way down and see how well this works let's just do one more example I would recommend you pause the video at this point and try to work this out and then you can resume it again and see how it works I'm going to assume you'll do that in your own timing here I need to figure out exactly which octet I want to focus on once again this is my key here I'm going to go ahead and figure this out 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 at sixteen seventeen eighteen nineteen Twenty twenty one twenty two two three twenty four twenty five twenty six twenty seven twenty eight twenty nine one two three that's right I'm left on here so I know we're focusing on the third octet the third octet now I can see you have some fields that can fill in one seven to ten sixteen one seven two loop sub sorry sixty ten sixty I just need to figure out what this number is and this number is in order to figure that out I need to find out what in the world is my network ID to stay consistent here we'll do this by ending dot I just need to figure this out and prints out the time now my little charts missing so maybe my brain won't like this so I'm going to go ahead and write it down like I said I would normally write this on a piece of paper this fellow said 1 2 4 8 16 32 64 128 now I just need to line this up I'm now translating the number 16 into binary I can't pulled 128 out of 16 or 64 or 32 but I can't pull 16 and the rest should be zeros so here's where we are done with this now all I need to figure out is exactly doing the process of ending again which ones equate with a 1 left in it zero zero zero one zero zero zero zero so it's pretty familiar right it looks like the top one still the fourth one over 1 2 3 4 the number is 16 so the next possible hop down the list here the magic number will give me that idea what it is that's of the fifth 1 over 1 2 3 4 5 that's 8 I would do 16 plus 8 that would tell me the next network ID in the list so the one before it must be the broadcast ID so 16 plus 8 minus 1 23 now the usable IP is in here or everything in between one seven to ten sixty dot seventeen one seven to ten sixty dot twenty-two now this is the usable range same type of process even a little less complicated the other one we're looking at or more depends on how you look at it but the key here is knowing which one I'm looking at and once I know the octet I'm focusing on I give them work on just translating that particular section don't have to worry about every single little bit especially when I mess up maybe some basic math and get myself in trouble and that has had the easiest way to get in trouble with a math that IP subnetting hopefully this information is helpful for you to be able to figure this out there's a lots of other tricks that are out there and we will be visiting other tricks here soon

Channel: Joshua Butcher

Views: 367,247

Rating: 4.8911414 out of 5

Keywords: Joshua Butcher, IP Subnetting, Subnetting, CIDR

Id: POPoAjWFkGg

Length: 16min 1sec (961 seconds)

Published: Wed Apr 09 2014