1 00:00:05,600 --> 00:00:11,010 Now analogies are okay but it's much better to demonstrate this practically using Packet Tracer. 2 00:00:11,020 --> 00:00:16,840 So let's actually build a network together and I'll show you how clients and service can work together 3 00:00:17,140 --> 00:00:20,650 and I'll show you that a client can also become a server. 4 00:00:20,710 --> 00:00:26,920 You could have two laptops one providing a service to another laptop so the laptop can be a server in 5 00:00:26,920 --> 00:00:28,840 some cases or it can be a client. 6 00:00:28,840 --> 00:00:30,740 In other cases. 7 00:00:30,820 --> 00:00:31,060 Okay. 8 00:00:31,070 --> 00:00:39,160 So in packet trace I'm going to go to end devices and I'm going to select a server and add it to my 9 00:00:39,160 --> 00:00:40,530 topology. 10 00:00:41,050 --> 00:00:45,670 I'll select a traditional P.C. and add it to the topology. 11 00:00:45,670 --> 00:00:52,870 Now these are symbols or representations of devices physically. 12 00:00:52,870 --> 00:00:56,200 This is a server physically that's a laptop. 13 00:00:56,200 --> 00:00:58,910 But logically that's what they look like. 14 00:00:58,960 --> 00:01:05,940 These are once again just symbols in an application like Packet Tracer in networking we use network 15 00:01:05,940 --> 00:01:10,200 diagrams to explain what a network looks like. 16 00:01:10,200 --> 00:01:16,440 Another example would be here where I'm using an application called Genius 3. 17 00:01:16,530 --> 00:01:21,420 So here's a Windows Server and here's a P.C.. 18 00:01:21,540 --> 00:01:27,070 Notice different symbols for different types of devices. 19 00:01:27,150 --> 00:01:30,150 I could change the symbol if I wanted to. 20 00:01:30,150 --> 00:01:36,960 So in this application I simply select a change symbol and then I could specify a nother type of symbol 21 00:01:37,230 --> 00:01:39,080 to represent a device. 22 00:01:39,120 --> 00:01:48,870 I notice there are many types of devices shown here but as an example I could say this is a server cluster. 23 00:01:48,870 --> 00:01:51,020 If it was a cluster of service. 24 00:01:51,300 --> 00:01:59,860 The point is is that a symbol is simply a logical representation for a physical device in Packet Tracer. 25 00:01:59,880 --> 00:02:08,700 If I click on this server there's a physical representation of the server and then I could once again 26 00:02:08,730 --> 00:02:15,930 change the symbol or icon used to represent that server 27 00:02:18,650 --> 00:02:22,650 here's the physical representation of the P.C. notice. 28 00:02:22,670 --> 00:02:23,950 Ethan it pulled right over there. 29 00:02:25,320 --> 00:02:31,520 So again this is a logical representation of a device. 30 00:02:31,530 --> 00:02:33,940 Now these two devices can communicate with each other. 31 00:02:33,990 --> 00:02:39,860 We either need to communicate using a physical cable or we need to communicate using the air. 32 00:02:39,870 --> 00:02:47,520 So what I'm going to do is select connections and I'll select what's called a crossover cable a crossover 33 00:02:47,610 --> 00:02:56,280 cable allows two pieces to talk directly to each other in the old days we had to use what was called 34 00:02:56,280 --> 00:02:59,730 a crossover cable to allow P.C. to talk to P.C.. 35 00:02:59,730 --> 00:03:01,530 Now today we don't have to do that. 36 00:03:01,620 --> 00:03:04,440 I'll discuss order MDI X late in the course. 37 00:03:04,560 --> 00:03:10,100 This used to be a problem in the old days it's not such a problem these days notice the interfaces have 38 00:03:10,100 --> 00:03:20,880 gone green but in packet trace if I delete that cable and then use just a standard ethernet cable 39 00:03:24,150 --> 00:03:30,150 notice the interface is down because Packet Tracer still expects you to use the right cable. 40 00:03:30,150 --> 00:03:39,220 So once again I'll delete that cable and I'll select a cross over cable copper crossover cable and connect 41 00:03:39,240 --> 00:03:44,510 fast ethernet on the P.C. to fast ethernet on the server. 42 00:03:44,590 --> 00:03:45,360 So there you go. 43 00:03:45,360 --> 00:03:46,650 I've built a network. 44 00:03:46,650 --> 00:03:49,170 That's an example of a network. 45 00:03:49,200 --> 00:03:54,440 It's a logical representation of a physical network. 46 00:03:54,500 --> 00:03:54,760 OK. 47 00:03:54,780 --> 00:03:59,760 But to allow these two devices to communicate with each other we need to have two things we need to 48 00:03:59,760 --> 00:04:05,940 have an ethernet address or MAC address that's pre-built into network interface codes. 49 00:04:06,060 --> 00:04:11,240 So a manufacturer will burn a MAC address onto a network interface code. 50 00:04:11,400 --> 00:04:15,090 You can change MAC addresses but generally you don't have to. 51 00:04:15,090 --> 00:04:16,600 They are globally unique. 52 00:04:16,620 --> 00:04:21,970 There have been cases where there have been duplicate MAC addresses but in general that isn't a problem. 53 00:04:22,020 --> 00:04:24,100 Every device has its own MAC address. 54 00:04:24,100 --> 00:04:30,770 So if I look at this P.C. and go to config go to foster Ethernet zero. 55 00:04:30,840 --> 00:04:37,670 Here is the MAC address of the P.C. you can see your mac address on a Windows computer as an example 56 00:04:37,670 --> 00:04:46,590 by going to control panel network and Internet network and sharing center. 57 00:04:46,600 --> 00:04:48,950 Have a look at your Adapter Settings. 58 00:04:49,120 --> 00:04:57,430 So as an example this Wi-Fi network adapter has this MAC address. 59 00:04:57,430 --> 00:04:59,860 That's its physical address or MAC address. 60 00:04:59,860 --> 00:05:03,450 You'll see something similar on an iPhone or other devices. 61 00:05:03,580 --> 00:05:10,240 Every device that communicates on physical Ethernet or communicates on Wi-Fi is gonna have a mac address 62 00:05:11,950 --> 00:05:18,190 we don't have to configure that again that's configured by default by the manufacturer on the server 63 00:05:18,670 --> 00:05:26,290 first Ethernet zero notice she has the MAC address of the server but what I'll do is change that so 64 00:05:26,800 --> 00:05:28,310 I'll change the MAC address. 65 00:05:28,300 --> 00:05:34,120 This is a twelve digit number in hexadecimal. 66 00:05:34,120 --> 00:05:39,460 Now I'll discuss hexadecimal and the details of this later in the course but for the moment just notice 67 00:05:39,460 --> 00:05:42,800 there are 12 numbers there hexadecimal numbers. 68 00:05:42,880 --> 00:05:46,700 So that's the MAC address now of the server. 69 00:05:48,930 --> 00:05:57,720 On the P.C. I'll change the MAC address as well and I'll make this a bunch of ones so triple 0 1 followed 70 00:05:57,720 --> 00:06:00,180 by eight ones. 71 00:06:00,210 --> 00:06:02,380 Now again you don't have to change the MAC address. 72 00:06:02,430 --> 00:06:08,540 I'm just doing that to make things simple now the second thing we need is an IP address typically in 73 00:06:08,540 --> 00:06:15,290 networks a server which could be a home router we'll be allocating IP addresses to your pieces using 74 00:06:15,290 --> 00:06:19,840 a protocol called Dynamic Host Configuration Protocol or DHEA P. 75 00:06:19,970 --> 00:06:29,630 So D.H. C.P. is allocating IP addresses to your P.C. P.S. I can see that here by opening up a command 76 00:06:29,630 --> 00:06:40,460 prompt and if I type IP config an IP address in this case IP version 4 is configured on my Windows laptop 77 00:06:41,150 --> 00:06:49,610 so those windows laptop has received an IP address automatically from a DHB server or it could be configured 78 00:06:49,610 --> 00:06:54,430 statically you can configure IP addresses statically in our little network. 79 00:06:54,440 --> 00:07:01,040 We don't have a router or another type of device so we have to manually configure the IP addresses. 80 00:07:01,400 --> 00:07:08,570 So on this first P.C. I'm gonna give it an IP address of tendered wandered wandered 1 and a subnet mask 81 00:07:08,570 --> 00:07:13,380 of 255 255 255 dot 0. 82 00:07:13,430 --> 00:07:19,120 Don't worry too much about IP addresses for the moment just understand that we've figured a MAC address 83 00:07:19,130 --> 00:07:22,370 you don't have to do that and I've configured an IP address. 84 00:07:22,670 --> 00:07:26,840 You don't have to do that if you've got two Windows laptops they can automatically communicate with 85 00:07:26,840 --> 00:07:29,750 one another here because of using Packet Tracer. 86 00:07:29,810 --> 00:07:38,450 I'm configuring the IP addresses manually Okay so if I go a desktop and open up a command prompt I'll 87 00:07:38,450 --> 00:07:42,250 make this a bit bigger and top the command IP config. 88 00:07:42,260 --> 00:07:46,080 What you'll notice is this P.C. has an IP address. 89 00:07:47,330 --> 00:07:49,020 I'll do something similar on the server. 90 00:07:49,040 --> 00:07:57,480 Let's give the server ip address of 10 dot wondered one to two and a subnet mask of 2 4 5 2 4 5 2 4 91 00:07:57,480 --> 00:07:58,500 5 0. 92 00:07:59,850 --> 00:08:07,260 So on the P.C. now I can use a special application called Ping to verify connectivity to the server. 93 00:08:07,260 --> 00:08:11,400 Ping is basically sending a message saying hello are you there. 94 00:08:11,520 --> 00:08:16,350 And then the servers replying back yes I'm here and the IS SAYING HELLO ARE YOU THERE. 95 00:08:16,350 --> 00:08:18,350 AND THE SERVER replies back yes I'm here. 96 00:08:18,690 --> 00:08:24,540 So basically it sends the he sends a message to the server saying Please reply if you're there and the 97 00:08:24,540 --> 00:08:30,090 server replies back saying Yes I'm here and it's used just to verify that the server is up is it there 98 00:08:30,180 --> 00:08:40,210 is it working is it turned on so on the P.C. I can use the command ping 10 1 1 2 and as you can see 99 00:08:40,210 --> 00:08:51,960 there we are getting a reply from 10 1 1 2 the pieces IP addresses this the servers IP address 100 00:08:56,270 --> 00:09:04,790 use the come on IP conflict to see it make this bigger is 10 1 1 2 Okay but that doesn't really prove 101 00:09:04,790 --> 00:09:10,880 anything except that my P.C. can ping the server that I've got IP connectivity to the server I basically 102 00:09:10,880 --> 00:09:16,000 sent a message to the server saying Are you there and the server reply back saying Yes I'm here. 103 00:09:16,310 --> 00:09:24,480 So this server is there but that doesn't really help us what we want to do is have a look at the services 104 00:09:24,480 --> 00:09:32,130 running on the server and notice here are a whole bunch of services we've got HDP as an example we've 105 00:09:32,130 --> 00:09:40,500 got DNS which is domain name system basically allows me to resolve domain names such as Google dot com 106 00:09:40,500 --> 00:09:51,130 or Facebook dot com to an IP address we've got other types of services here like email FCP and various 107 00:09:51,130 --> 00:09:52,420 other services. 108 00:09:52,630 --> 00:10:02,050 So on the HP Service I'm going to leave this on that's the default on the P.C. if I close this command 109 00:10:02,050 --> 00:10:13,620 prompt down and open up a web browser and deletes bras using HDP Hypertext Transfer Protocol to the 110 00:10:13,620 --> 00:10:16,760 IP address of the server. 111 00:10:16,800 --> 00:10:22,710 What you'll notice is a web page displays I can see a small Web page here which says hello world. 112 00:10:22,710 --> 00:10:28,300 I can go back I can go look at an image page and he has a Cisco logo. 113 00:10:28,300 --> 00:10:31,930 Now that doesn't really do much but that's an example of a network. 114 00:10:31,980 --> 00:10:37,290 We've got a client on the left a server on the right. 115 00:10:37,380 --> 00:10:44,430 The server is configured with the HP Service and it's serving a web page to the client when the client 116 00:10:44,430 --> 00:10:46,650 requested the web page. 117 00:10:46,650 --> 00:10:58,740 If I turn the service off so I've turned it off now for HDP but it's on for HDP s HDP has once again 118 00:10:58,740 --> 00:11:06,840 just an encrypted version of hypertext transfer protocol which is used for web browsing. 119 00:11:06,840 --> 00:11:17,210 I'll close this down open it up again try and go to HDP 10 dot wandered one dot too. 120 00:11:17,580 --> 00:11:21,810 Now what will happen and it might take it a while is it will time out and there you go. 121 00:11:21,810 --> 00:11:28,230 Notice it says request timed out and that's because the server is no longer listening on port 80. 122 00:11:28,230 --> 00:11:29,190 It's not listening. 123 00:11:29,210 --> 00:11:32,190 So it just basically drops the traffic that you send to it. 124 00:11:32,370 --> 00:11:36,340 So view Senator request saying show me a web page on port 80. 125 00:11:36,420 --> 00:11:42,000 It just basically drops the request ignores what you what you're asking. 126 00:11:42,060 --> 00:11:49,620 If I go HDP s however notice we get to the web page because the server is listening on Port 443 now 127 00:11:50,280 --> 00:11:57,740 which is the port number used for HDP s of enable HDP once again. 128 00:11:58,200 --> 00:12:03,930 And let's try and go to the server on port 80 and that's worked. 129 00:12:04,410 --> 00:12:09,990 So just to prove it because that wasn't very clear I'll open up a web browser again and manually type 130 00:12:10,380 --> 00:12:16,500 HDP tendered wandered 1 to 2 and notice the web page displays. 131 00:12:16,680 --> 00:12:21,810 Now another great thing about packet tracer is we've got the simulation mode. 132 00:12:22,020 --> 00:12:26,370 If I select a simulation mode I can actually see what's going on. 133 00:12:26,610 --> 00:12:33,390 So on the P.C. and I'll just move this around so we can see what's going on. 134 00:12:33,390 --> 00:12:42,210 I'm gonna click Go now and what you'll notice is a packet has been sent into the network. 135 00:12:42,210 --> 00:12:47,160 Now there's a lot of information here and I'll go through this in more detail when we talk about the 136 00:12:47,160 --> 00:12:49,950 OSA model and the TCB IP model. 137 00:12:49,950 --> 00:12:57,210 But what I'd like you to see is we've got a mac address which is the MAC address of the P.C. sending 138 00:12:57,210 --> 00:13:03,060 traffic to the MAC address of the server and we've got an IP address which is the IP address of the 139 00:13:03,060 --> 00:13:10,830 P.C. going to the IP address of the server source IP addresses P.C. destination IP address is the server 140 00:13:11,280 --> 00:13:18,630 at least to here we've got an ether net had a source MAC addresses the P.C. destination MAC address 141 00:13:19,020 --> 00:13:20,580 is the server. 142 00:13:20,580 --> 00:13:26,740 Notice here we've got port 80 port 80 once again is the port number that the server is listening on. 143 00:13:27,120 --> 00:13:31,050 If we look at that in more detail and don't get scared by this. 144 00:13:31,050 --> 00:13:35,010 This is just an example of the kind of data that's sent into the network. 145 00:13:35,080 --> 00:13:35,660 Why shock. 146 00:13:35,660 --> 00:13:40,670 We'll show you this in more detail than this but this gives you an idea of what's going on. 147 00:13:40,800 --> 00:13:47,970 Source MAC address is the P.C. destination MAC address is the server we've got source IP address P.C. 148 00:13:48,270 --> 00:13:54,770 destination ip addresses the server we're using IP version for here we're also using a protocol called 149 00:13:54,820 --> 00:14:00,900 TTP or transfer control protocol that basically just gives us reliability in a network transmission. 150 00:14:00,930 --> 00:14:06,800 So if you sent something to a server and it gets lost it'll be reset re transmitted. 151 00:14:06,900 --> 00:14:09,150 So it gives us reliability. 152 00:14:09,330 --> 00:14:11,490 Destination Port number is 80. 153 00:14:11,550 --> 00:14:21,770 So when we send that into the network that will be sent to the server and the server will receive that. 154 00:14:22,020 --> 00:14:27,990 And then what it will do is send something back to the P.C. 155 00:14:37,790 --> 00:14:43,480 so a packet gets sent back from the server to the P.C. with information. 156 00:14:43,650 --> 00:14:49,510 Notice the source port for the reverse traffic from the server to the P.C. is 80. 157 00:14:49,530 --> 00:14:55,140 Basically the client talks to serve on port 80 and then the server replies back from port 80 to a port 158 00:14:55,140 --> 00:14:59,510 number that your client has randomly decided to use. 159 00:14:59,550 --> 00:15:05,140 Now that's a lot of information and I'm hoping it's not too overwhelming the best thing you can do is 160 00:15:05,140 --> 00:15:11,830 install packet tracer and build a topology yourself and follow what I'm doing. 161 00:15:11,890 --> 00:15:16,330 There's no better way to learn than to do things yourself. 162 00:15:16,330 --> 00:15:18,940 One of my favorite analogies is riding a bicycle. 163 00:15:18,970 --> 00:15:21,190 I can talk about riding a bicycle. 164 00:15:21,340 --> 00:15:28,220 I can show you pictures videos etc but until you yourself ride a bicycle fall off a few times struggle 165 00:15:28,220 --> 00:15:30,570 a bit you'll never learn to ride a bicycle. 166 00:15:30,580 --> 00:15:35,830 Best way to learn is to just do it so bold as yourself and try it yourself.