Subnet Saturday #2: Meet the Mask | Cisco CCNA 200-301

[Music] and welcome everybody to subnet Saturdays we're gonna focus on IP addresses from the ground up or I should say maybe from layer three up it's great to have you a couple days ago I was walking I recorded this this office here in Las Vegas and I was just leaving I was in a hurry and so a self-inflicted wounds were the worst and so I was I had my hand in the doorframe kicked the door open and I was paying attention something else in the full way of the door slammed on those two fingers yeah I was like please let the stop party as much as it does and it did so after about 15 minutes it stopped like hurting really really bad I can still feel my heartbeat in that finger and this one so let's hope the best for my fingernail anyway great to have you here now I'm I'm not hoping but I'm presuming that if you haven't had the chance already after this livestream after the session if you haven't watched the one previous to that I've encouraged you to do that as we take a look at ipv4 addresses and how they work and I've got a I've got a little challenge I like you to help me solve and that's this let's go to us go to a lab environment it's always good to start off with a practical environment here so here is a computer it happens to be running Windows 10 and I'm gonna put command prompt and the command prompt could be either powershell or command prompt with or without escalating privileges just a windows 10 computer and let's do the command ipconfig and press enter now if we did IP config space slash all that would give us some more information which is helpful including information such as what is the DHCP server and was the layer to address all those really good things but right here is showing us that this is the IP address and I wanted to just do a quick reminder about some of the things we know about IP addresses and also about this little thing below it which is called the mask so every device that's configured to operate and work on an IP version 4 Network is gonna have an IP version 4 address and always and a mask associated with it so I'd like to do just a quick recap regarding IP addresses and also these same things apply to them as well so it's a two-part aspect so the first element is that an IP version 4 address is for numbers long and and so is the mask so the IP address is four numbers long and so as the masks they're both four numbers long and they go together each number in an IP version 4 address and each number in an IP version 4 mask is going to be in the range somewhere between 0 and 255 so we have those are both in common between the IP address which has the two parts to it network and host and the mask which is the dividing line so each of those numbers in both the IP version 4 address and the mask are separated by a period so if we took a look at that in the interface check this out right here we have the IP address which is 10.16 0.10 so for decimal numbers separated by periods and then we have the mask which is also for decimal numbers separated by period all right so far so good and here's an example of those ranges so in an IP version 4 address and it's associate IP version 4 mask if any of those numbers are higher than 255 something is terribly wrong so it's they're gonna be somewhere in the range we're not gonna use every possible combination of numbers in that range but that's the range for numbers for the IP address separated by periods for numbers in the mask separated by periods also also that's often referred to as dotted decimal two dots being the three periods and the decimal numbers being the base 10 numbers a numbering system we use most people in the planet all right so here's the key for the mask and here's an example of a mask in this mask it has three as four numbers 255 dot 255 dot 255 dot zero and I'd like to share with you what that means in measurable terms it's the mask like this what it means and I'm gonna use a little example from our previous session it means this in the mask they make sure that's an area in the mask anywhere there's a 255 that means the corresponding number from the IP version 4 dress is the part of the network address so if we had this mask associated with an IP address that would mean that the the first number and the second number and the third number over here would all represent the actual network and then when the 255 stop that's the dividing line and that's how it works so everything to this side after the 255 is in the now stop mean yeah the mask says yeah those are those are those that part of the IP addresses used for host addressing and that's how the dividing line that's all we're gonna start this discussion that's how the dividing line works between the IP network address over here and the host portion on this side over here all right let's take a look at an example of that I put these in order so I can pick them up later for Neetu so an IP version 4 address has two parts network over here somewhere host over here somewhere and the dividing line is the mask and we're gonna take a look at some examples of that 255 in action on a few dresses so let's go back to this computer right here this computer is 10.16 0.10 that's the IP address and here is the mask 255 255 255 dot 0 so if we took that literal IP address and in the background I'm bringing queuing that up here we go so we took that IP address of 10.16 dot 0 dot ten this bad boy right here and we had this mask associated with it which I'll line up excuse me just a moment I do that that's pretty much lined up it would look something like this in fact that's just what we saw on the Windows 10 computer if the IP address on the computer of 1016 dot 0 10 and most importantly this mask which is saying that based on the 255 s in this first number in the mask this part is the network and based on this 255 the mask this part of the IP address is the network and based on these 255 in this part of the mask this part is the network with this mask means that this computer is that 10.16 dot 0 that's the network like the street name and then the host address like the house number on that street is 10 and that's how it works are you ready for a challenge let's do this let's download I'm das mat command prompt or PowerShell either way good work and let's do an IP config and press enter and this guy's address right here on this network interface card is 192 168 dot one dot one hundred and so just to put that in real terms let me bring that up there's this IP address 192 168 1 dot 100 boom that's a dotted decimal IP version 4 address and part of this beautiful IEP address part of this is the network something on this side and a part of this is the actual host or house number over on the site and based on what we learned in the previous session and reviewed today the dividing line is gonna be based on the mask so if we look at the mask the mask is this 255 which means the first number from the IP address is network the second number of 255 means that the second number from the IP address from the computer is the network and the third number of 255 in the mask represents to this third number the one here in the IP address of that computer is the network and then a 0 to the last number somebody means that the last number of the computer the IP address on that computer on this device is a host address or like a house number so we could say at this computer and this server in this case then this this applies also to whether it's an Android device or iOS device or a Linux box or a Macintosh or a Windows computer IP version 4 addresses works the same on all these devices so in this case you'd be saying that the IP address is this guy and the mass can we get their correct mask out here is this one so that something means that the dividing line is right here all of this 192 once you take one is the network because the mask says so everywhere there's a 255 the corresponding number in the IP address is represented as part of the network address so if we had other customers other devices other computers maybe a Windows machine maybe a internet camera or whatever it is on this same network they would have to have the same first three numbers to be considered to be logically on that same street so if we had a printer on the same network in the same VLAN on this 192 one state one network is IP to start with 192 168 1 dot something maybe 101 105 720 298 something in the you know that's available here in the host addressing but the key is this 192 wants to take one is just like a street name and the way the mask and the way we're going to start this discussion is that the mask any was a 255 it means that corresponding part of the customers IP address is the network and it pretty much works just like this going back to my visualization of the mask they bring that down there we go that works there we go just like that so there we color-coded it so in computer networks and devices they don't color code it for us they just give us the mask and then we were able to you know the computers doing calculations and to identify that mask better the human we can just visually see that the first three octets are the network based on the mask and the last octet over here is the actual host portion no I just realized I said something that may be new to a few of you and that is Keith you just said octet whoa octet what does that mean well octet is just another way of representing eight bits eight something so in every number these numbers in this IP address behind the scenes this decimal number of 10 it's really made up of eight bits that represent it we're gonna do a binary discussion in a separate video we'll work up to it and this number here 16 is represented by 8 bits and this number right here is represented by 8 bits in this case they're all gonna be off like lights which is because it has a zero value and this is gonna be represented by 8 bits so sometimes we refer to each those numbers in the range of 0 through 255 as octet because behind the scenes there actually represent about 8 bits and same thing with the mask the mask every number in house is gonna be represented by 8 bits so if I if I slip and say the word octet before we were quite ready that's what I'm referring to if I say octet things like oh that's one number one dot decimal represented number in an IP version 4 address so what I thought would be really fun to do is let's take a look at a few examples to reinforce this and oh yeah yeah we could do this and then like she do some live demos of how we can change the mask and actually change what the network is based on that hosts IP address all right so let's go to the interface this is a the Windows Server we did IP config here and it showed us the IP address and the mask great so this computer believes based on the mask that this is the network ID live on street 192 168 1 who knew and my host address says this computer if you asked him is dot 100 and that's because in that last octet that last number the corresponding number in the mask was 0 it ain't hey this is all a host addresses right here none of it represents the actual network or street name ok so that's on a Windows Server here is a Windows 10 client which it the command is the same IP config there's the IP address there's the mask and if we think to ourselves are these two computers this Windows 10 computer and the Windows Server are they on the same network and we could say something like well the Windows server thinks he's on 192 168 1 this network with the mask indicating that this portion of the network address and the client is at 10:16 0 10 and based on its mask it thinks that this is the network and so those two devices aren't wildly different IP networks which also implies that they are on different layer 2 VLANs and I switched environment so in order for the client to be able to talk to the server or the server to talk to the client because around different IP networks they are gonna have to use something that looks like this and has the icon of a Cisco router or similar to make that forwarding decision because that's how traffic is moved between networks go ahead and oh my is that so for traffic to flow between Bob the client right here at 10 16 0 10 and based on his mask he thinks this is the network and a server which I will draw in here SRV are at one ninety two dot one sixty eight dot one dot one hundred that's its IP address so the client when it's tries in the Paquette to that device would say whoa I'm on 10:16 zero and I'm trying to reach based on the IP address of the destination a computer in a very different Network even when one little aspect off like this is 191 if this was like just one number off in the first three octet first two numbers the PC would say oh he's on a different network and as a result he would forward at layer two to his default gateway who would then open it up look at the layer three destination address make a routing decision and then forward the packet on its way and there may be multiple layer three routers in the path so Robert one may need to spell in this case Robert one maybe he said in the router two and router two may need sent the router 3 and route 3 may have connectivity to that 192 wants to see it one network or 192 wants to date ones that 0 network and the Billy to route packets at layer 3 is the reason why the client has the ability to actually talk to a server on a different network outside of his local VLAN ok so you know what I'd I'd love to do oh my gosh this is gonna be so fun I like I just realized I had you on the side of my head on that whole discussion like yeah look at this look at this oh how embarrassing is that let me give you a quick recap I was drawing routers and going at it and didn't have the camera on the right on the right angle all right that's fun and embarrassing all at once well here's the drawing ideas true so this client here the client PC if it is on the 10 16 0 Network it tries to reach a device on the 192 168 1 network it's gonna have to forward it to a router I'll pay more attention to my buttons going forward this is live alright so what I would like to do is let's take a look clear off the screen and let's take a look at this router right here and play some games with that router regarding IP addresses and to do this let's go ahead and use a loopback interface I had somebody chat saying Keith may be taught about loopback interfaces in the any of your content yet YouTube but I thought you know I don't know that I have so on this router there's like gig 0/0 that's a physical interface in the in the video we did on inter VLAN routing with a router we took a look at logical sub interfaces for inter VLAN routing with router on a stick that was fun but we could also create other logical layer three interfaces and one of those types is called a loopback so we could just say interface loopback and then we can pick a number between like zero and eleventy billion I'll pick loopback zero and we press ENTER and that creates this logical loopback interface which we can then assign to a given IP address to and play with and there's other there's reasons in routing why we use loop X and we'll touch more about why and how and so forth but for this discussion what I like to do is let's create an loopback interface on router 1 and on that loopback interface what we can do is assign some IP addresses so let's imagine that let's go ahead use the address 10.16 dot 67 83 and what we can do is we can play with the masks we can use a mask of 255 0 dot 0 dot 0 which would mean to the router hey I'm on the 10 network or we can use a mask of 255 dot 255 dot 0 dot 0 which would mean hey I'm on the 1016 Network or we can use a mask of 255 dot 255 dot 255 dot 0 and the router would think hey I'm on the 10 about 16,000 67 Network that's literally how it works we just changed the mask to identify how much of that customers IP address so we're here's the mask how much of that IP address represents the street or the network address and how much of it represents the actual host address whatever is left over so I'm gonna jot that down 10.16 dot 67 283 because we're gonna go ahead and create that and then demonstrate it changing right before our eyes based on the mask being changed so let me go ahead and clear that off and hide that and let's go to an interface look at a router one so here on router 1 let me see if I can find him he's somewhere not there ok so this is my management computer and let's go to router 1 okay so this is router 1 it's a show IP interface brief just to see where we're starting whoa look at that everything's down down do be you do down down which is the people for a Cisco router so all the interfaces are down no IP addresses so let's go ahead and let's create an interface loopback I'll spill it out here interface move back and here's the range a lot so I agree it's logical loopback interface now if we do it the show now we have that new loopback interface right there so it's a logical interface a layer 3 logical interface doesn't have an IP address it is up we just created it from thin air and now let's go ahead and assign an IP address to it all so let's do this let's do a show IP route now I'm adding the do command if you're fairly new to Cisco and the iOS interface you have a command line interface sometimes called the CLI if we're in configuration mode the show commands don't work at least in this version of the iOS unless we add the do command in front of it so instead of exiting so step magazine global config and our interface can figure it out to the privilege mode prompt and then doing the show command then going on there back we just tack on it'll do in front and then it allows us to do the show command the negative though is that it doesn't always mm depending on the version of iOS it doesn't give us that context-sensitive help if you're doing a do in front of it like with a question mark so if you know the command or you know exactly what you want to type in it's handy to not have to go back and forth all right but I digress let's take a look at do show IP route to look at the IP version 4 routing table look at that this router just doesn't have any clue on how to reach any networks and that's because two things it doesn't have any interfaces that have IP addresses and even if these others did if they're administratively shut down they're not functional not usable so let's do this let's add an IP address to this interface and we are currently an interface loopback 0 that's just to confirm we're on the right interface and let's give it an IP address the syntax is IP address and then the address of 1060 and I am I am looking at my notes right here because I want to make sure I put the IP address we planned on which is 10 1667 83 all right 10.16 dot 67 dot 83 and my question for you is regarding this IP address which part of this IP address this IP version 4 address 4 numbers separated by three periods often called dotted decimal which part of this represents the network ID and which part represents the actual host address and the answer we heard zero and an English that means that this number ten represents the network ID network 10 da and the host address based on the last three zeros of the mask bank are the last three numbers I'm asking zero represent the host address being 16.7 67 83 and then we'll press Enter duh I love it and we'll do a show now check this out now that now that we have an IP address a layer 3 logical IP address on an interface that's up on this router this router believes I know how to get to that network and we can ask it say hey mister router how do you know which networks you can reach and the answer to that is in the command show IP route and they'll show us the routing table on this device let's do it so we'll do a show up to come in configuration mode show IP route press enter and this says that I am directly connected to this 10 network so here it shows us 1000 with a slash 8 we'll talk more about why it shows a mask of 2 55000 this one right here as a slash 8 we'll do that when we get into another session with with binary for now I want to just focus on the fact that it has it believes that our out to the 10 network now if we change that IP address and we change well change the mask so it used to be 10 1667 a3 if we change that second number of the masta to 2 to 255 easy for me to say now it says that these first two once we press Enter so in Cisco IOS when you type in a command and you press Enter this is good and bad it immediately goes into what's called the running config in router says right I'm going so as long as the syntax isn't wrong we don't get an error it immediately takes hold of that and starts working at it once we press Enter the only exception of that is on a layer 2 switch or multi or switch when you create a VLAN it actually doesn't create the VLAN until you exit VLAN configuration mode but that's just a weird exception that nobody cares about but now you know all right so these first two octet these first two numbers are now going to be the network and the last two numbers will be the host address so we'll press enter and there we go IP address 10:16 67 83 and the mask as the two numbers are the network 1016 is the network and that means the host address is 67 83 and if we did it again fun game and we did 255 for that third octet like that now it means to the router that this interface is connected to the 10.16 dot 67 network that's the street name and the actual house number or host address is 83 and that's how that works all right now to verify some of that let's do this let's do the show IP interface or loop back and I'll spell this out show IP interface or a loopback 0 and what that's gonna do is kind of show us a lot of details about that loopback 0 interface that we just configured but the part I wanted to focus on was this the Internet address is 10.16 dot sixty seven eighty three and here it's showing us 24 bits now bear with me for about a couple more sessions and we'll clearly identify why the mask of two why the mask of 255 255 right here why this mask of 255 255 mm its last 24 they mean the same thing behind the scenes because there's actually 24 bits in order that are representing the mask bit for now I want to show you that twenty five two five two five means that the first three numbers are the network address actually you know what we can do let me see if I can pull this out of hat there's a way there's a so I did see CIA training for many years and you know we learn these little tricks and tips I think there's a way let me see if if you bear with me there's a way I think that we can have this show us instead of showing a site or notation for the mask like this to have it show us actually decimal let's see here I okay as I recall what we do is this they just show users so show users simply says that I'm locked onto the Bob in this lab and this is my current session and I'm connected to line console 0 so if I get a line console 0 this would also work if you're connected via vty line so line console 0 holy schnikeys I wish I knew that was I'll take it I'll take the easy win so this command IP oh yeah yeah Wow I have not used this command probably eight or nine years um IP net mask format oh yeah there we go baby uh if we sit I want to see this in decimal then in our output for the show IP interface instead of things last 24 for that mask it'll actually show us the dotted decimal mask and it's done so let's do a show IP interface for loopback zero all right excuse me a fun chuckle because I'm just so glad when things like that work out we could also look at the running config and the running config it would also show up as and dotted decimal for the mask so this means that 10 16 10 16 67 is the network address and I just heavy I copied and pasted that accidentally with the right-click my bad there we go so that I get out of there so that means that 1016 67 this computer believes is the network address that loop x0 is on and that based on the mask and the host address is 83 so if we did a show IP route and I'm going to say pipe exclude I just don't want to see the local routes just for now so that basically doesn't show IP route but anywhere there's a line that has a capital L in it it just emits it so this lets us focus on the route so here we ever out for the 10 network with a 20850 check that up let me actually do it without the l ah I didn't realize he would do that to what this is doing it's actually because we did that dotted decimal format display for the line console 0 it's also showing us the dotted decimal mask in the routing table so for alerting purposes pretty darn convenient okay so here it's showing us that it knows it's on 10 1667 network based on this mask and it's directly connected so that is what I wanted to share with you in this in this progressive video regarding ipv4 and meeting the mask so in the previous session we identified some of the basics for an IP version 4 address and in this time we took a look at how the mask puts up the dividing line between the network portion somewhere over here and the host portion and it does that with the dividing line is where the 255 end and that's we're gonna start with as we continue we'll take a look at some additional options and tweaking and custom subnetting and vlsm but that's a little common for now we know that the IP address is two parts Network portion host portion we know that the mask is the dividing line if the 255 in the mask corresponds to the number and the IP address that's Network 255 in the mask corresponding to the second number Network 255 corresponds to the third number network that means the first three numbers of the IP address by the network the street and the last number with the zero and the mask means hey that's all host address information like 10 for the client and that's that's what I wanted to cover today I've also gotten some great feedback from the from posts and comments and I read all this and I've I've taken some really interesting feedback that made me think about a few things I thought yeah this could be made just that much better by doing this or that the other so I appreciate all that feedback and if you ever want to catch up or look at the full playlist just go to my channel if you haven't already please do now take a moment and subscribe and hit the alert bells you know when new live streams come in and I'll be adding those strategically the playlists so I'm gonna have a playlist for the full CCNA well not full season a bit everything that I do in live streams for CCNA I'll have it there so you know my channel go to playlists and everyone for CCNA and I'm also gonna carve out one for CCNA related security like dynamic ARP inspection DHCP snooping port security at which of the three main ones for CCNA and then I also have a playlist for for the like the meat and potatoes and also one for subnets Saturdays so the master one I'll have everything I'll put in the right order that way you can just go to the playlist go down in order say oh yeah that looks great that looks great or if you need to like fill in some gaps we're talking about trunking and you haven't covered trunking yet you just go back to that video in the playlist and enjoy it and if you have a chance to study with a friend I recommend doing it it's a lot more fun to study with somebody and have that banter going back and forth and chat and really press each other to understand also I recently have been on reddit I left reddit alone for a long time I forgot how amazing that is there is a subreddit for CCNA and it's fantastic a lot of great questions a lot of great feedback like how was your experience and and what all this and what about that the new CCNA starting in that started - February 24 2020 which is based on my clock here is coming up but soon after this recording is live that'll be a thing of the past and the new CCNA is consolidated in my opinion it is simpler than the other CCNA they didn't try to include all the wireless and all the security from CCNA Wireless CCNA security and CCNA Raulerson put all that in to one it's more of a do you understand how these things work and can you do basic configuration from the blueprint which I don't have in front me physically but in the blueprint when you look at the CCNA blueprint if it has tasks like configure just be prepared to be able to really configure it if it's OSPF or whether it's some other technology if it says configuring the blueprint you'd want to do some hands-on practice with packet tracer or hands-on labs or virtual labs or or any revive gear if you have that but do the practice because if it says configure that's a telltale sign they're gonna be asking maybe a simulation or knowledge that you would have gained by doing the hands-on practice with that technology if it says describe here's my approach if it says describe something and you have the option of getting a little practice with it I still remember commend practicing because I'm I'm often shocked by seeing a technology labbing it up and then having it not respond as I thought it might and then taking a look maybe even going with the protocol analyzer and saying what what's going oh that's what's going on and better understanding it based on I'm getting hands on so that's it I appreciate you joining me for this section on subnetting where we're meeting the masks I've got another livestream tomorrow the topic will be announced on social so you can just track that and join me for that as well it'll be CCNA related and then going in forward into Wednesday I've got another great topic that were going to do as well also I had a request for some additional spanning-tree so we do have a spending tree section already in there and it was a you know it's the entry level type of spending tree and I and the question was can he go it's just a little bit more detail on a couple little aspects so the answer is yeah and it would be applicable to CCNA as well so I want to do that all right so let me get some exit music and I'll play that and for everybody who's joining me live or watching this after the fact thanks for joining the channel thanks for supporting other people thanks for putting in an effort to make the world a better place by you being a better technician your betters able to support your family your friends your employer and all the content that we're learning now just basic nuts and bolts of IP addressing and how networks operate that will still be extremely valuable when in five years you're in the cloud and you're working on software-defined networks because a lot of these concepts including IP addressing and how forwarding works it works the same way except we're not physically located of the gear we're configuring stuff up in the cloud or for your service provider providing cloud services somebody's racking and stacking and configuring the VLANs and all that all those pieces in the cloud so that when the customer just goes to click a button says I want this server and this network behind the scenes through network automation and also some physical gear in place all that's taking place so technicians are gonna be required to facilitate all that and you me a big part of that by just starting out and continue learning all right thank you very much for joining me and I'll see you in the next video [Music] [Music] [Music] [Music] [Music] [Music] [Music] [Music] [Applause] [Music] [Music] you [Music]

Channel: Keith Barker

Views: 16,416

Rating: 4.9761434 out of 5

Keywords: cbt nuggets, cbt training, ccna, ccna 200-301, ccna certification, ccna study, ccna training, cisco, cisco ccna, cisco certifications, cisco training, subnetting, subnet mask, subnetting tutorial for beginners, subnet mask and ip address, subnet mask explained, subnetting in computer networks, subnetting made easy, subnet, ip

Id: IQ2XzWAqiHc

Length: 36min 30sec (2190 seconds)

Published: Sat Jan 18 2020