06 Ccna Data Center 640 - 911 network layer addressing

00:00:00 - Do you remember when we were discussing in the brief 00:00:04 - history of ethernet CBT Nugget in this particular series that 00:00:08 - we had a Layer 2 address in the ethernet world called the 00:00:13 - MAC address. 00:00:15 - And this address would identify a station uniquely on 00:00:19 - the network. 00:00:20 - Think of it like a social security number 00:00:23 - in the United States. 00:00:25 - This is a number in the US that uniquely identifies every 00:00:29 - US citizen for financial stuff. 00:00:33 - Well, guess what? 00:00:34 - At the network layer of the OSI model, we have addressing 00:00:38 - there as well. 00:00:40 - This is also going to uniquely identify a system. 00:00:44 - And it is network layer addressing that is the subject 00:00:49 - of this particular Nugget. 00:00:51 - At the network layer of the OSI model is the IP protocol. 00:00:56 - And I want to go ahead and review some key parameters of 00:00:59 - the internet protocol with you in this Nugget. 00:01:02 - We'll then delve into and dissect our IP addresses. 00:01:06 - We'll see how some of these IP addresses are for public 00:01:11 - internet usage. 00:01:12 - While the vast majority of them now are going to be for 00:01:16 - private utilization. 00:01:18 - We'll talk about DHCP and DNS. 00:01:21 - And then we'll go ahead, and we will wrap up this 00:01:25 - particular action-packed Nugget with a look at some 00:01:29 - tools that you would definitely want in your tool 00:01:31 - belt when it comes to testing and troubleshooting your 00:01:36 - network layer addressing, otherwise known, of course, as 00:01:40 - IP addressing. 00:01:42 - Let's jump in. 00:01:44 - So what should we keep in mind about the 00:01:46 - internet protocol in general? 00:01:48 - Well, as you know from the title of this particular 00:01:51 - Nugget, this is, indeed, a network layer protocol. 00:01:56 - So this is Layer 3 of our famous OSI model. 00:02:00 - Now, engineers like to refer to it as connectionless. 00:02:05 - And what this means is it's going to be a best effort 00:02:10 - style of delivery. 00:02:11 - So for reliability, the internet protocol will not be 00:02:17 - the protocol in the stack that is utilized. 00:02:21 - We already know of one higher in the stack, right? 00:02:24 - At the transport layer, there's TCP-- 00:02:27 - the transmission control protocol. 00:02:30 - It would be a mechanism to give us reliability. 00:02:33 - Internet protocol says, hey, I don't want the overhead 00:02:37 - associated with reliability. 00:02:39 - I'm just going to be moving packets at the network layer 00:02:43 - as quickly and efficiently as possible. 00:02:47 - Now, the internet protocol does, indeed, feature 00:02:51 - addressing. 00:02:53 - And that is really the main subject of this particular 00:02:57 - Nugget, isn't it? 00:02:58 - We want to examine the IP addressing in great detail. 00:03:05 - Now, an IP address is a 32-bit identifier. 00:03:10 - So that's the first thing we really want to have committed 00:03:12 - to memory, right? 00:03:13 - This is a 32-bit address. 00:03:17 - So if you were to look at one of these in binary, it would 00:03:22 - be a string of zeros and ones. 00:03:27 - Notice here's eight bits, one, two, three, four, five, six, 00:03:32 - seven, eight. 00:03:33 - Those eight bits are in what are called the first octet of 00:03:38 - the IP address. 00:03:40 - Then we have eight more bits, for example. 00:03:44 - And these are the next bits in the next octet. 00:03:49 - And this is going to go on for 32 occurrences. 00:03:54 - Now, as you know, this would be very, very cumbersome for 00:03:58 - us humans to deal with IP addresses in this manner. 00:04:03 - So what do we do? 00:04:04 - We go ahead, and we take the IP address. 00:04:08 - And we represent it in decimal, which 00:04:12 - we are so used to. 00:04:14 - And we take the octets. 00:04:16 - And we separate them with a period. 00:04:20 - So this is called dotted decimal notation. 00:04:27 - Now, something else that I want you to understand about 00:04:31 - the IP address is the fact that it is hierarchical. 00:04:36 - What? 00:04:38 - By the way, it took me many, many years of training in the 00:04:41 - IT field to be able to say hierarchical correctly. 00:04:46 - What hierarchical means is that a portion of the IP 00:04:52 - address is going to identify the network that we are on. 00:04:58 - And a portion of the IP address is going to represent 00:05:03 - a particular host system. 00:05:06 - So hierarchical means that it's not just a flat address 00:05:11 - with one meaning. 00:05:12 - There is different meanings within the 32-bit IP address. 00:05:20 - By the way, a great analogy that you can use for this is a 00:05:25 - street address. 00:05:27 - Sure, here in the United States a street address will 00:05:31 - have a house number and then a street name. 00:05:36 - Sure enough, the street name is like the network portion of 00:05:41 - the IP address. 00:05:43 - And the house number is like the host 00:05:46 - portion of the IP address. 00:05:49 - Now, when the IP protocol was designed, the designers had a 00:05:53 - very straightforward idea. 00:05:55 - They said, OK, we're going to need addressing 00:05:59 - for very large networks. 00:06:02 - And they called these Class A networks. 00:06:05 - They said, we'll need addressing for 00:06:07 - medium-sized networks. 00:06:09 - And they called these Class B. And we'll need addressing for 00:06:14 - small networks. 00:06:15 - And they called these Class C networks. 00:06:19 - By the way, there is a Class D. And that is for multicast 00:06:24 - transmissions. 00:06:26 - We mentioned multicast in an earlier Nugget in this series. 00:06:29 - And of course, multicasting has to deal with sending 00:06:33 - information to a group of recipients. 00:06:36 - We can distinguish that group of recipients by the 00:06:40 - particular multicast address group that they join. 00:06:44 - And then, by the way, there is a Class E that the designers 00:06:49 - reserved for experimental purposes. 00:06:52 - They didn't give these addresses out for 00:06:56 - organizations or individuals to use. 00:06:59 - Now, to create a Class A address space, what they did 00:07:03 - was they took the first bit of the first octet and they 00:07:08 - forced it to a zero setting. 00:07:11 - So we have a zero in the first bit of the first octet. 00:07:15 - And then you have a bit, another bit, another bit. 00:07:19 - So there's the first four, five, six, seven, eight. 00:07:23 - So those are bits that are in the first octet of a Class A. 00:07:28 - And again, the point here is the very first bit 00:07:32 - is forced to a zero. 00:07:35 - Now, that's the first octet. 00:07:37 - Then we have our decimal point, right? 00:07:40 - And then you would have eight host bits, eight host bits, 00:07:45 - and eight host bits. 00:07:47 - So you see the idea here? 00:07:49 - There are seven bits really that we have for 00:07:53 - identification of networks. 00:07:56 - Really, though, it's that whole first 00:07:58 - octet we consider it. 00:07:59 - So there's eight bits for identification of networks. 00:08:03 - And then there's 24 bits for host identification. 00:08:09 - Remember, we said they designed the Class A address 00:08:12 - space with large network environments in mind. 00:08:16 - Wow. 00:08:17 - I'll say. 00:08:18 - There's 24 bits that are available for host addressing 00:08:25 - on that particular network. 00:08:27 - You might ask, how many hosts does that accommodate on a 00:08:32 - particular network? 00:08:33 - Well, let's get the calculator and find out. 00:08:37 - It turns out there's a formula that we want to memorize for 00:08:40 - how many hosts we can accommodate 00:08:43 - given a number of bits. 00:08:45 - And that formula is 2 raised to the number of 00:08:49 - host bits minus 2. 00:08:52 - Yeah. 00:08:53 - So if we get out our scientific calculator, we can 00:08:56 - determine how many hosts we could accommodate 00:09:00 - on a Class A network. 00:09:01 - Watch this. 00:09:02 - I'll go to a scientific view. 00:09:05 - And I'll say 2 x to the y 24 equals. 00:09:13 - And then I'll subtract 2 from that. 00:09:17 - Look at this. 00:09:18 - On a Class A network, there are 16,777,214 00:09:30 - host addresses available. 00:09:33 - Let me repeat this, because it may seem a bit 00:09:36 - unbelievable to you. 00:09:38 - On a Class A network, there are 16,777,214 00:09:47 - host addresses available. 00:09:50 - Now, could we put even close to that number? 00:09:54 - Could we put a million hosts in one LAN segment? 00:09:58 - No way. 00:10:00 - We would have such an issue with broadcast propagation 00:10:04 - that performance would be an absolute nightmare. 00:10:08 - And that's why we take addresses, and we subnet them. 00:10:13 - Yeah. 00:10:14 - This is the reason behind subnetting. 00:10:18 - If we have a Class A address space, we want to subnet it to 00:10:23 - break it up into smaller networks. 00:10:27 - Pretty cool. 00:10:28 - How about a Class B? 00:10:30 - Well, in the Class B addressing format, they forced 00:10:34 - the first two bits. 00:10:36 - The first two bits are forced to 10. 00:10:41 - Then you have your other bit settings in that octet. 00:10:46 - Then you have your decimal. 00:10:47 - And guess what? 00:10:49 - You also have network bits in the second octet. 00:10:55 - And you've got eight of those. 00:10:57 - Then you have your host addresses 00:10:59 - and your host addresses. 00:11:01 - So there's 16 bits for the identification of networks. 00:11:06 - And there is 16 bits for the identification of hosts in a 00:11:12 - Class B. 00:11:13 - So we've got a lot more Class B networks that were defined. 00:11:17 - And they can host quite a few workstations, obviously not as 00:11:23 - many as the Class A. Let's check it with the 00:11:26 - formula why don't we? 00:11:28 - So if we clear this, and we say, 2 x to the y 16 minus 2, 00:11:36 - we discover that in a Class B network, we can have 00:11:40 - addressing available for 65,534 host machines. 00:11:47 - Pretty cool. 00:11:48 - Now, how about the Class C? 00:11:50 - In the Class C, they forced the first three 00:11:53 - bit settings to 110. 00:11:55 - Then we have the remaining bits that are going to be 00:11:59 - utilized to identify the network. 00:12:03 - Then we have the next octet, which is full of network 00:12:09 - addresses or network bits. 00:12:11 - Then we have the third octet full of network bits. 00:12:15 - And then just the last octet is left for hosts. 00:12:19 - So sure enough, we have 24 bits for network addressing. 00:12:24 - We can make a lot of different Class C networks. 00:12:27 - And each of those networks can have eight bits utilized for 00:12:32 - host addressing. 00:12:34 - We go back to our calculator. 00:12:36 - We could actually do this one in our head. 00:12:38 - But we'll just use the calculator, being lazy. 00:12:41 - We'll say 2 x to the y the 8 host bits. 00:12:45 - We'll subtract our 2. 00:12:47 - And we discover 254 hosts are possible on a Class C network. 00:12:57 - So lots to learn here about our address classes inside IP 00:13:04 - addressing. 00:13:05 - Now, think about this. 00:13:06 - We said that in a Class A, they were forcing that first 00:13:12 - bit position to a zero. 00:13:15 - Does this impact the possible values in that first octet? 00:13:21 - Absolutely. 00:13:23 - Yeah, sure, this is going to impact the possible decimal 00:13:27 - value in the first octet of an IP address. 00:13:31 - Specifically, the value for a Class A in the first octet in 00:13:37 - decimal is going to be 1 to 126. 00:13:44 - You know what's interesting? 00:13:45 - It's actually 127. 00:13:48 - But they said, we're going to reserve 127 for testing in IP 00:13:55 - addressing. 00:13:56 - And this is reserved for what's called 00:13:58 - the loopback address. 00:14:00 - Yep. 00:14:00 - So it's actually just going to be 1 to 126 in the first octet 00:14:06 - that identifies a Class A address. 00:14:10 - For the Class B address, we said they were going to force 00:14:15 - the first two bits to 10. 00:14:18 - And this makes it a decimal 128 to 191 that is possible in 00:14:25 - the first octet. 00:14:26 - So if we see an IP address, and it has a, let's say, 129 00:14:31 - in the first octet, we know that technically it's part of 00:14:35 - the Class B space. 00:14:37 - The Class C, well, remember, we said the first three bits 00:14:42 - will be forced to 110. 00:14:46 - And that's going to amount to a 192 through a 223 as 00:14:52 - possible in the first octet. 00:14:54 - Once again, we see an IP address with, let's say, 200 00:14:59 - in the first octet. 00:15:00 - We'll know it's part of the Class C space. 00:15:05 - So by examining the first octet of an IP address, we can 00:15:11 - easily determine what class of address that particular IP 00:15:17 - address belongs to. 00:15:19 - Let's practice with this. 00:15:21 - I just brought up the command prompt. 00:15:22 - And I'll do an IP config, which is an easy way at the 00:15:27 - command prompt on a Windows box for us 00:15:29 - to see our IP address. 00:15:31 - Here is my IP address-- 00:15:33 - 192.168.32.1. 00:15:37 - Let me highlight that just to make absolutely certain that 00:15:40 - you're seeing it. 00:15:41 - So here is my IP address-- 00:15:43 - 192.168.32.1. 00:15:46 - Now, I look at the first octet value of 192. 00:15:51 - And sure enough, 192 falls in that range, doesn't it, of 00:15:58 - Class C. So the class of address assigned to my 00:16:03 - workstation is, indeed, a Class C address. 00:16:09 - Now, remember, we said the IP address is hierarchical. 00:16:13 - That means of our 32 bits, we have some of those that 00:16:19 - identify the network and some of those that identify a host. 00:16:24 - Now, for a Class A, we said the first eight 00:16:28 - identify the network. 00:16:30 - And then we have 24 that are going to identify 00:16:34 - a particular host. 00:16:35 - What really determines this? 00:16:38 - And if we want to subnet and, let's say, have 10 bits 00:16:43 - identify the network and 22 bits identify a host, how can 00:16:48 - we do that? 00:16:49 - Well, the answer is the subnet mask. 00:16:53 - That's right. 00:16:54 - The subnet mask is 32-bit number. 00:16:58 - It is reported in conjunction with the IP address. 00:17:02 - It's configured with an IP address. 00:17:05 - And its job is a simple one-- 00:17:08 - to distinguish which of the 32 bits are identifying the 00:17:14 - network and which of the 32 bits are identifying a 00:17:18 - particular host on that network. 00:17:22 - So we have default subnet masks for our different 00:17:27 - classes, don't we? 00:17:28 - And you know what? 00:17:29 - You really already know what they are. 00:17:32 - You know that the subnet mask for Class A would have to mask 00:17:37 - off the first octet. 00:17:39 - And it does this with all binary ones. 00:17:44 - And then it does all zeros for the remaining bits. 00:17:49 - What does this work out to in decimal? 00:17:52 - 255.0.0.0. 00:17:57 - Yeah. 00:17:57 - That's masking off the first eight bits to identify a 00:18:01 - particular network. 00:18:03 - The unmasked bits are identifying a host. 00:18:07 - And there's 24 of them. 00:18:08 - And they're all zeros. 00:18:10 - Wow. 00:18:10 - You know a Class B then. 00:18:12 - Class B would be 255.255.0.0, because we said the Class B 00:18:22 - has the first two octets identifying 00:18:26 - a network by default. 00:18:27 - And finally, the Class C. The Class C would be 255.255.255.0 00:18:37 - for a subnet mask. 00:18:40 - And again, first 24 bits identifying networks. 00:18:44 - And just those last eight bits identifying a 00:18:47 - host on that network. 00:18:50 - When we subnet our IP addresses, we are 00:18:55 - taking these masks. 00:18:57 - And instead of using the default mask, we are 00:19:00 - extending the mask. 00:19:02 - So for instance, if I were to subnet a Class C, I'd go 00:19:06 - 255.255.255 maybe like 240. 00:19:12 - And notice, we are utilizing bits in the fourth octet in 00:19:16 - order to identify sub networks. 00:19:20 - Let's jump back to our computer here and see its 00:19:23 - subnet mask. 00:19:26 - So here we are in the command prompt. 00:19:28 - And I'll do my IP config once again. 00:19:31 - And sure enough, below our IP address, we can see our subset 00:19:38 - mask, can't we? 00:19:39 - I'm going to circle the IP address and the subnet mask. 00:19:43 - And look at this. 00:19:44 - The subnet mask for our Class C address is, indeed, the 00:19:50 - default Class C mask. 00:19:53 - So we're not doing any subnetting on this particular 00:19:58 - home network that I'm on right now. 00:20:01 - Now, think back a moment in this Nugget when we said that 00:20:05 - the formula for figuring out how many hosts we could have 00:20:08 - on a network would be 2 raised to the host bits minus 2. 00:20:12 - Where did that minus 2 come from? 00:20:14 - Well, it's a couple of reserved addresses. 00:20:18 - There are several reserved addresses we're 00:20:20 - going to talk about. 00:20:20 - But those two right there are specifically the case of what 00:20:26 - we call the network address. 00:20:29 - This is when we have all zeros in the host bits. 00:20:35 - Yeah. 00:20:36 - This isn't a valid address for a particular 00:20:39 - system on our network. 00:20:42 - You can't have all zeros in your host bits. 00:20:45 - So one of the numbers that we're minusing here is for 00:20:51 - that occurrence. 00:20:52 - Another one is the broadcast address. 00:20:56 - The broadcast address is when we put all 00:21:00 - ones in the host bits. 00:21:02 - And this is to send and what we call a directed broadcast 00:21:07 - into that particular network. 00:21:09 - So why the minus 2? 00:21:12 - Well, we just showed you right there. 00:21:14 - It's the network address-- all zeros in the host bits. 00:21:18 - The broadcast address-- all ones in the host bits. 00:21:21 - Can't have that. 00:21:22 - Not valid for host addressing. 00:21:24 - What are some other reserved addresses? 00:21:28 - Well, the local broadcast is a reserved address. 00:21:33 - And you know what it is? 00:21:34 - It's all ones in the entire 32-bit IP address. 00:21:40 - So this address right here is reserved-- 00:21:44 - 255.255.255.255. 00:21:48 - Totally can't use it, because it is reserved to send out a 00:21:52 - broadcast to everyone on that particular LAN segment. 00:21:57 - I already mentioned loop back. 00:22:00 - It's reserved. 00:22:01 - The entire 127 space is reserved. 00:22:06 - And another famous reserved address 00:22:09 - is a Microsoft invention. 00:22:12 - It's the auto configuration address. 00:22:16 - It's what a machine will give itself for an address. 00:22:19 - If it doesn't have a DHCP server, it can rely on to get 00:22:24 - one automagically configured. 00:22:26 - This reserved address is 169.254 blah, blah, blah, 00:22:32 - blah, blah. 00:22:33 - So if we see this address on one of our Windows machines, 00:22:38 - we'll know we failed to get an IP address automatically and 00:22:42 - that this auto configuration address has been put in place. 00:22:47 - Now, the internet and TCP/IP-connected computers 00:22:52 - have become so amazingly popular, in fact, think about 00:22:56 - all the iPads and tablets and Android phones and iPhones out 00:23:02 - there in the world that all want IP addresses for purposes 00:23:06 - of connecting to the internet. 00:23:09 - This has become such a popular craze that 00:23:13 - we're out of addresses. 00:23:15 - Yeah. 00:23:16 - And one of the clever ways in which they addressed this 00:23:20 - address shortage was to reclaim some of the IP address 00:23:25 - space and make it private, make it only usable behind a 00:23:33 - router and in the home or a corporate office. 00:23:38 - First, let's memorize the ranges they did it A, B, and C 00:23:45 - for private. 00:23:46 - If you have an address that begins with 10 and then has 00:23:51 - anything following it, this is a private Class A address. 00:23:58 - Routers on the public internet will not route this. 00:24:03 - It's private use only. 00:24:05 - The B range that they reserved is 172.16 to 172.31, 00:24:18 - technically .255.255. 00:24:20 - So notice it's from 172.16 anything to 172.31.255.255. 00:24:29 - So it stops at 172.32. 00:24:33 - And then for Class C, they reserved 192.168.0.0 all the 00:24:42 - way up to 192.168.255.255. 00:24:49 - So if we wanted to go ahead and create a home network, we 00:24:55 - could just pull from the Class C. 00:24:58 - We could say, all right, I'm going to do 192.168.11.0 with 00:25:06 - a 24-bit mask as the network address space for my entire 00:25:13 - home network. 00:25:14 - We can accommodate 254 machines on this network, as 00:25:19 - we calculated earlier. 00:25:21 - And notice this /24 is just a clever way to abbreviate the 00:25:28 - subnet mask. 00:25:30 - I'm using 24 bits in that subnet mask. 00:25:34 - This abbreviated notation is called prefix notation. 00:25:39 - And we love it as a convenient way to 00:25:43 - represent the subnet mask. 00:25:46 - We need to memorize these reserved private IP addresses. 00:25:53 - Now, it really is unfair of me to talk about the private IP 00:25:57 - addresses without talking to you about how we could 00:26:00 - actually use them. 00:26:02 - You see if I go ahead and I use the private IP address 00:26:08 - space for the three computers in my home-- 00:26:11 - so this is, let's say, 192.168.11.1. 00:26:17 - This is .2. 00:26:18 - And this is .3 all in 192.168.11. 00:26:22 - What I do is with my home Linksys router is I go ahead 00:26:29 - and translate these with what is called network address 00:26:34 - translation into a real usable IP address, a non-private IP 00:26:43 - address on my router. 00:26:45 - Where do I get that IP address from? 00:26:49 - Well, from my internet service provider. 00:26:51 - Sure, my internet service provider can say, here you go. 00:26:54 - Here's a public IP and go ahead and network address 00:27:01 - translate your inside privately addressed machines 00:27:06 - into that public address. 00:27:10 - Now, it's time for us to talk about another technology here 00:27:13 - with IP addressing. 00:27:14 - And that's DHCP-- 00:27:17 - the dynamic host configuration protocol. 00:27:20 - This is how the internet service provider can 00:27:24 - automatically assign my router with its public name space. 00:27:32 - Pretty cool. 00:27:33 - By the way, the DHCP process is a four-step process. 00:27:39 - My router will broadcast a discover message, saying, 00:27:46 - help, I need an address. 00:27:48 - The internet service provider can go ahead 00:27:53 - and provide an offer. 00:27:57 - Then the router will send a request 00:28:02 - message for that address. 00:28:04 - And then the internet service provider will send an 00:28:09 - acknowledgement of that assignment. 00:28:13 - This is a four-step process that is often memorized with 00:28:17 - the mnemonic device of DORA. 00:28:21 - Yeah. 00:28:21 - I always think of the popular US cartoon that helps students 00:28:26 - learn Spanish when I think of this four-step process-- 00:28:29 - discover, offer, request, and acknowledgement or DORA. 00:28:34 - So DHCP, network address translation, these are all 00:28:39 - very important protocols that are going to assist the 00:28:44 - internet in its functionality and even private networks in 00:28:48 - their functionality. 00:28:50 - One more technology that we wanted to mention here, of 00:28:53 - course, is DNS. 00:28:55 - DNS is how we can map a name to an IP address. 00:29:01 - When you go to www.cisco.com, you're obviously going to some 00:29:09 - public IP address. 00:29:12 - The DNS system is like your yellow pages, resolving a 00:29:17 - public IP address to a particular name. 00:29:22 - Pretty cool. 00:29:23 - All of these protocols working together in order to make 00:29:27 - intranets and the internet a reality. 00:29:32 - Now, as you've seen in this Nugget, the world of IP 00:29:36 - addressing is fairly complex and complicated. 00:29:39 - Fortunately, we are provided with a great set of tools for 00:29:45 - managing and supporting the world of network addressing. 00:29:50 - One of them we already have witnessed. 00:29:52 - It's the ipconfig command in order to see our IP address 00:29:59 - and our subnet mask. 00:30:01 - Notice another piece of information we like to view 00:30:04 - with this is the default gateway, the address of our 00:30:08 - local router on the segment. 00:30:12 - Now, with ipconfig, if you want even more information, 00:30:18 - you can do the /all keyword. 00:30:22 - Now, we're getting even more information about the IP 00:30:26 - configuration. 00:30:28 - By the way, if you are getting your information dynamically 00:30:33 - from a DHCP server like I am, then you can go ahead and 00:30:38 - refresh that information by saying, ipconfig/release. 00:30:45 - Now, I just lost all my information and my connection 00:30:49 - to the internet. 00:30:50 - And now, I can say ipconfig/renew in order to 00:30:55 - obtain new Windows IP configuration information. 00:31:01 - So ipconfig, ipconfig/all, ipconfig/release, and 00:31:10 - ipconfig/renew are all great tools for your tool belt. 00:31:17 - Notice took a little bit of time there. 00:31:20 - And I was getting nervous. 00:31:21 - But I did renew my particular DHCP information for TCP/IP. 00:31:28 - Now, another great tool is ping, the 00:31:30 - packet internet groper. 00:31:33 - Really, that's its name. 00:31:34 - Crazy, huh? 00:31:35 - The packet internet groper will reach out and see if it 00:31:39 - can communicate with a particular machine. 00:31:41 - 192.168.1.1 is my local router. 00:31:46 - Look at this. 00:31:47 - I am able to communicate with that local router. 00:31:50 - In fact, I'm able to do it very, very efficiently. 00:31:56 - By the way, if we go into the Properties of this command 00:31:59 - prompt here and we say Quick Edit Mode, you can literally 00:32:04 - highlight and copy from your command prompt. 00:32:07 - So let me use that to highlight the fact that we 00:32:10 - pinged 192.168.1.1. 00:32:14 - And we sent four test packets. 00:32:17 - And we got a reply all four times. 00:32:21 - And the round-trip time was under one millisecond. 00:32:24 - So not only can we get to our local router, but we can get 00:32:29 - to our local router very efficiently. 00:32:32 - Awesome. 00:32:33 - We sent four packets. 00:32:35 - Four were received. 00:32:37 - And zero were lost. 00:32:38 - I like it. 00:32:40 - Watch this. 00:32:41 - I'll ping yahoo.com. 00:32:45 - Now, this is kind of interesting because we're 00:32:47 - testing more than just our reachability to 00:32:50 - the internet here. 00:32:51 - We're also testing DNS, aren't we? 00:32:54 - Yeah. 00:32:54 - The name www.yahoo.com was resolved with DNS to 00:33:01 - 98.139.180.149. 00:33:05 - Notice a public Class A IP address. 00:33:10 - And notice all four of the packets made it. 00:33:15 - Notice it takes more time to communicate with yahoo.com. 00:33:19 - On average, it took 62 milliseconds in order for me 00:33:24 - to communicate out to that internet resource. 00:33:28 - So ping, hugely valuable. 00:33:31 - Now, watch this. 00:33:33 - This is also very cool. 00:33:35 - I'm going to do a trace route to yahoo.com. 00:33:40 - And what we will attempt to see is each router hop that we 00:33:46 - take to get there. 00:33:48 - There is my home router. 00:33:50 - Then it looks like we went to a Tampa, 00:33:52 - Florida, Verizon router. 00:33:55 - Then another Tampa, Florida, Verizon router. 00:33:58 - Then another Tampa, Florida Verizon router. 00:34:01 - Then we hit some backbone router up in Atlanta. 00:34:06 - And now, we see we're stuck. 00:34:09 - What's happening here is for the next hop is our trace 00:34:14 - route is probably being blocked by someone from a 00:34:18 - security perspective. 00:34:20 - Yeah. 00:34:20 - From a security standpoint, they're saying, we're not 00:34:23 - going to allow trace routes through our gear. 00:34:26 - So we are losing the path information at that point. 00:34:30 - But keep in mind that you could use trace route in your 00:34:35 - own network where you control all of the equipment. 00:34:39 - And you would be able to see full path information. 00:34:45 - So I don't know about you, but I really do identify this as a 00:34:49 - pretty important Nugget. 00:34:50 - We took a look at network layer addressing. 00:34:54 - We really zeroed in on those IP addresses, didn't we? 00:34:58 - We saw there was a big, big difference in public and 00:35:01 - private IP addresses. 00:35:03 - And we wrapped up by talking about such important utilities 00:35:08 - like DHCP and DNS. 00:35:10 - And we examined some awesome tools that we 00:35:13 - have in our tool belt. 00:35:15 - We've got IP config with its various switches. 00:35:18 - We've got ping. 00:35:20 - And we've got trace route all there at our disposal when we 00:35:25 - are supporting and we are maintaining IP-based networks. 00:35:31 - Well, I hope this has been informative for you. 00:35:33 - And I'd like to thank you for viewing.