1 00:00:00,000 --> 00:00:01,260 In this section of the course, 2 00:00:01,260 --> 00:00:03,000 we're going to discuss routing. 3 00:00:03,000 --> 00:00:05,100 Now, up to this point, we've covered a lot of things, 4 00:00:05,100 --> 00:00:06,930 but our network traffic really hasn't even left 5 00:00:06,930 --> 00:00:08,670 our local area network yet. 6 00:00:08,670 --> 00:00:10,830 Now, once we're ready to leave our local area network, 7 00:00:10,830 --> 00:00:11,730 this is where routers 8 00:00:11,730 --> 00:00:13,770 are going to really start coming into play. 9 00:00:13,770 --> 00:00:14,603 When we start talking 10 00:00:14,603 --> 00:00:16,440 about connecting to subnets within our network 11 00:00:16,440 --> 00:00:19,200 or connecting our internal network with an external network, 12 00:00:19,200 --> 00:00:20,970 we have to use a router. 13 00:00:20,970 --> 00:00:22,590 Now, the first thing you must understand 14 00:00:22,590 --> 00:00:24,030 is the function of a router, 15 00:00:24,030 --> 00:00:25,980 which is simply to route traffic. 16 00:00:25,980 --> 00:00:27,240 Now, I know that sounds really silly, 17 00:00:27,240 --> 00:00:29,160 but essentially it is going to forward traffic 18 00:00:29,160 --> 00:00:30,480 in one direction or the other 19 00:00:30,480 --> 00:00:31,710 between different subnets, 20 00:00:31,710 --> 00:00:33,420 between internal and external networks, 21 00:00:33,420 --> 00:00:35,760 or between two different external networks. 22 00:00:35,760 --> 00:00:37,500 Now, each subnet or external network 23 00:00:37,500 --> 00:00:39,420 is going to be on its own broadcast domain 24 00:00:39,420 --> 00:00:42,240 because routers are used to separate broadcast domains. 25 00:00:42,240 --> 00:00:44,580 Unlike a switch which are layer 2 devices, 26 00:00:44,580 --> 00:00:47,400 a router will be able to split up a broadcast domain. 27 00:00:47,400 --> 00:00:49,350 With a switch, you only have one broadcast domain 28 00:00:49,350 --> 00:00:51,180 for everything that you're going to connect to it. 29 00:00:51,180 --> 00:00:53,370 But with routers, since they're layer 3 devices, 30 00:00:53,370 --> 00:00:55,050 they can separate and break those apart 31 00:00:55,050 --> 00:00:58,020 into smaller broadcast domains and these smaller portions 32 00:00:58,020 --> 00:01:00,810 give us more efficiency and security in our networks. 33 00:01:00,810 --> 00:01:03,000 Now, let me take a quick detour our here for a second 34 00:01:03,000 --> 00:01:04,890 because I need to provide you with an important warning 35 00:01:04,890 --> 00:01:07,290 for the real world versus the exam. 36 00:01:07,290 --> 00:01:09,930 Now, in the real world, you can use a layer 3 switch 37 00:01:09,930 --> 00:01:12,090 or a multi-layer switch, as it's also known, 38 00:01:12,090 --> 00:01:14,100 to perform routing functions too. 39 00:01:14,100 --> 00:01:15,840 Many small office home office networks 40 00:01:15,840 --> 00:01:18,000 or small office and medium sized businesses 41 00:01:18,000 --> 00:01:20,310 are going to opt to use layer 3 switches 42 00:01:20,310 --> 00:01:22,530 because they can handle both layer 2 forwarding 43 00:01:22,530 --> 00:01:25,020 when they act like a switch and layer 3 routing 44 00:01:25,020 --> 00:01:26,460 when they act like a router. 45 00:01:26,460 --> 00:01:28,830 Now, for the exam though, I want you to remember, 46 00:01:28,830 --> 00:01:30,750 if you're using a multilayer switch, 47 00:01:30,750 --> 00:01:32,280 it is functioning as a router, 48 00:01:32,280 --> 00:01:35,220 so we're going to call it a router on the exam. 49 00:01:35,220 --> 00:01:36,630 Now, in this entire section, 50 00:01:36,630 --> 00:01:38,970 whenever you hear me use the word router, 51 00:01:38,970 --> 00:01:40,680 even if you're using a layer 3 switch 52 00:01:40,680 --> 00:01:42,960 or a multi-layer switch to perform those functions, 53 00:01:42,960 --> 00:01:44,730 we are still talking about a router 54 00:01:44,730 --> 00:01:46,560 because that's the part of that device 55 00:01:46,560 --> 00:01:47,460 that we're really covering 56 00:01:47,460 --> 00:01:49,650 when we talk about routing in this section. 57 00:01:49,650 --> 00:01:52,320 Now for the exam, if they simply use the word switch 58 00:01:52,320 --> 00:01:53,580 in any of the questions, 59 00:01:53,580 --> 00:01:55,230 they're referring to a regular switch 60 00:01:55,230 --> 00:01:57,780 that operates at layer 2 of the OSI model. 61 00:01:57,780 --> 00:01:59,850 If on the other hand, they use the term router, 62 00:01:59,850 --> 00:02:02,130 multi-layer switch or layer 3 switch, 63 00:02:02,130 --> 00:02:04,140 they're referring to the layer 3 functionality 64 00:02:04,140 --> 00:02:07,170 of that device, which we refer simply as a router 65 00:02:07,170 --> 00:02:09,990 during both this course and your official exam. 66 00:02:09,990 --> 00:02:13,410 Now, let's talk about how a basic router process works. 67 00:02:13,410 --> 00:02:15,420 Let's consider a small network diagram here 68 00:02:15,420 --> 00:02:18,180 with two networks, one on the left and one on the right. 69 00:02:18,180 --> 00:02:20,850 Now as you can see, PC1 is connected on the left side 70 00:02:20,850 --> 00:02:23,340 and PC2 is connected over on the right side. 71 00:02:23,340 --> 00:02:24,840 To connect these two networks together, 72 00:02:24,840 --> 00:02:26,910 we have two routers with a serial connection 73 00:02:26,910 --> 00:02:29,250 or a wide area network connection between them. 74 00:02:29,250 --> 00:02:31,230 For now, we're not going to focus on the connection 75 00:02:31,230 --> 00:02:33,210 between them as much because we're going to cover that 76 00:02:33,210 --> 00:02:34,680 when we talk about WAN technologies 77 00:02:34,680 --> 00:02:36,330 in a different section of the course. 78 00:02:36,330 --> 00:02:38,340 But for now, I just want you to realize there is 79 00:02:38,340 --> 00:02:40,410 some kind of a connection between these two networks, 80 00:02:40,410 --> 00:02:42,720 whether that's a fiber connection, a serial connection, 81 00:02:42,720 --> 00:02:45,300 a satellite connection, a VPN or some of the link, 82 00:02:45,300 --> 00:02:46,920 it really doesn't matter right now. 83 00:02:46,920 --> 00:02:49,710 Just know there is a connection between those two networks 84 00:02:49,710 --> 00:02:52,050 and we're going to have to use two routers, one on each side 85 00:02:52,050 --> 00:02:54,390 to communicate over that WAN connection. 86 00:02:54,390 --> 00:02:56,190 Now, if I'm sitting on PC1 87 00:02:56,190 --> 00:02:58,110 and I want to send a message over to PC2, 88 00:02:58,110 --> 00:03:01,020 I can't just send it out an ARP like I did with a switch. 89 00:03:01,020 --> 00:03:02,490 If you remember back in switching, 90 00:03:02,490 --> 00:03:04,110 we talked about how PC1 would send 91 00:03:04,110 --> 00:03:05,520 an ARP packet to the switch, 92 00:03:05,520 --> 00:03:07,170 and if it didn't know where to deliver it, 93 00:03:07,170 --> 00:03:09,210 it would send it out to every other switch port 94 00:03:09,210 --> 00:03:10,470 based on the MAC address, 95 00:03:10,470 --> 00:03:13,650 and then PC1 could and will start to do that, 96 00:03:13,650 --> 00:03:16,230 and they'll be able to get from here using the ARP request 97 00:03:16,230 --> 00:03:17,700 to figure out how to get from the switch 98 00:03:17,700 --> 00:03:20,100 and the switch realizes it doesn't know the MAC address 99 00:03:20,100 --> 00:03:21,450 associated with the request, 100 00:03:21,450 --> 00:03:23,910 so it forwards it out to its default gateway 101 00:03:23,910 --> 00:03:26,400 and that default gateway, that's a router. 102 00:03:26,400 --> 00:03:28,830 Then that router is going to respond to the ARP request 103 00:03:28,830 --> 00:03:30,900 on behalf of the destination device. 104 00:03:30,900 --> 00:03:33,690 At this point, we now are going to leave MAC addressing behind 105 00:03:33,690 --> 00:03:35,340 because MAC addresses are only used 106 00:03:35,340 --> 00:03:38,070 internally to our network using layer 2. 107 00:03:38,070 --> 00:03:39,510 As soon as we get to the router though, 108 00:03:39,510 --> 00:03:42,300 we're switching over to IP addresses or logical addressing, 109 00:03:42,300 --> 00:03:44,160 which operates at layer 3. 110 00:03:44,160 --> 00:03:45,420 Now, this is where we begin to make 111 00:03:45,420 --> 00:03:47,910 our layer 2 to layer 3 transition happen. 112 00:03:47,910 --> 00:03:50,460 At this point, PC1 has determined that the MAC address 113 00:03:50,460 --> 00:03:51,540 for where the router is, 114 00:03:51,540 --> 00:03:53,520 because it needs to send any packets there 115 00:03:53,520 --> 00:03:55,650 that it wants to get out of this local network. 116 00:03:55,650 --> 00:03:57,000 The left router in this case, 117 00:03:57,000 --> 00:03:59,310 is going to want to send the information over to PC2 118 00:03:59,310 --> 00:04:01,830 because that's what PC1 asked it to do. 119 00:04:01,830 --> 00:04:03,540 Now, to do that, it's going to pass the information 120 00:04:03,540 --> 00:04:04,650 over to router two, 121 00:04:04,650 --> 00:04:06,720 and then router one will get the data frame, 122 00:04:06,720 --> 00:04:08,880 which is layer 2 from PC1, 123 00:04:08,880 --> 00:04:10,920 the router will repackage it as a packet, 124 00:04:10,920 --> 00:04:13,770 which is layer 3, and then add an IP header. 125 00:04:13,770 --> 00:04:15,690 This allows router one to then push that data 126 00:04:15,690 --> 00:04:18,180 over its default connection as an IP packet, 127 00:04:18,180 --> 00:04:20,430 and then data will be sent across the serial connection 128 00:04:20,430 --> 00:04:21,899 over to router two. 129 00:04:21,899 --> 00:04:23,700 Now, once the packet gets to router two, 130 00:04:23,700 --> 00:04:25,770 router two will strip off that IP header 131 00:04:25,770 --> 00:04:28,110 and bring it back down to layer two data frames 132 00:04:28,110 --> 00:04:30,990 and add the MAC address for PC2 that correlated 133 00:04:30,990 --> 00:04:33,810 with the destination IP of that packet that it received. 134 00:04:33,810 --> 00:04:37,410 Now, because router two knows the MAC address for PC2, 135 00:04:37,410 --> 00:04:40,050 it can call up to PC2 directly over layer 2 136 00:04:40,050 --> 00:04:42,240 and send that data frame over to the switch. 137 00:04:42,240 --> 00:04:43,740 The switch will then take that information 138 00:04:43,740 --> 00:04:46,290 and push it from router two down to PC2, 139 00:04:46,290 --> 00:04:48,630 just as if it was two computers on the same switch 140 00:04:48,630 --> 00:04:50,430 trying to communicate with each other. 141 00:04:50,430 --> 00:04:53,460 Now, whenever PC2 wants to send response back to PC1, 142 00:04:53,460 --> 00:04:55,140 the process will simply be reversed 143 00:04:55,140 --> 00:04:57,120 and the communication continues back and forth 144 00:04:57,120 --> 00:05:00,540 between PC1, its switch, router one, the WAN connection, 145 00:05:00,540 --> 00:05:03,270 router two, its switch, and PC2. 146 00:05:03,270 --> 00:05:04,800 Now a quick summary of what we just saw 147 00:05:04,800 --> 00:05:06,240 in terms of data flows. 148 00:05:06,240 --> 00:05:08,220 We started out with layer 2 information 149 00:05:08,220 --> 00:05:11,010 we called a data frame going from PC1. 150 00:05:11,010 --> 00:05:12,330 When it got to router one, 151 00:05:12,330 --> 00:05:14,280 it was then packaged in a layer 3 thing, 152 00:05:14,280 --> 00:05:15,570 which we call a packet 153 00:05:15,570 --> 00:05:17,520 and sent across our wide area network. 154 00:05:17,520 --> 00:05:18,810 When it got to router two, 155 00:05:18,810 --> 00:05:20,790 it's going to strip it back down to layer 2 156 00:05:20,790 --> 00:05:23,910 and use MAC addresses to deliver it over to PC2. 157 00:05:23,910 --> 00:05:27,450 Essentially, this is how routing works at its simplest form. 158 00:05:27,450 --> 00:05:28,283 Now, at this point, 159 00:05:28,283 --> 00:05:30,570 I've given you a very simple example of how routing works, 160 00:05:30,570 --> 00:05:32,250 but it gets a lot more complicated 161 00:05:32,250 --> 00:05:34,710 as we start to move packets across not just direct WAN links 162 00:05:34,710 --> 00:05:37,290 like the one you saw here, but over other WAN links, 163 00:05:37,290 --> 00:05:38,670 like the internet. 164 00:05:38,670 --> 00:05:40,650 Now, we're going to be discussing routing in this section, 165 00:05:40,650 --> 00:05:43,320 and we'll be focused on Domain 1 Networking Concepts 166 00:05:43,320 --> 00:05:45,630 and Domain 2 Network Implementation. 167 00:05:45,630 --> 00:05:47,550 We're going to cover Objective 1.4, 168 00:05:47,550 --> 00:05:48,990 which states that you must be able to explain 169 00:05:48,990 --> 00:05:51,180 common network ports, protocols, services, 170 00:05:51,180 --> 00:05:52,470 and traffic types. 171 00:05:52,470 --> 00:05:54,360 We'll also cover objective 2.1, 172 00:05:54,360 --> 00:05:55,800 which states that you must be able to explain 173 00:05:55,800 --> 00:05:58,170 characteristics of routing technologies. 174 00:05:58,170 --> 00:06:00,390 First, we're going to look at some routing fundamentals 175 00:06:00,390 --> 00:06:02,100 as we cover the basics of how routing works 176 00:06:02,100 --> 00:06:03,360 inside of our networks. 177 00:06:03,360 --> 00:06:05,280 Then, we'll discuss routing tables, 178 00:06:05,280 --> 00:06:06,120 which are used to determine 179 00:06:06,120 --> 00:06:07,530 which direction your data should be sent 180 00:06:07,530 --> 00:06:09,480 as it attempts to cross from one subnet 181 00:06:09,480 --> 00:06:11,820 or local area network over to another. 182 00:06:11,820 --> 00:06:12,810 Next, you're going to learn 183 00:06:12,810 --> 00:06:14,670 about the different types of routing protocols that we use 184 00:06:14,670 --> 00:06:17,550 inside of our networks, including RIP, OSPF, 185 00:06:17,550 --> 00:06:19,500 BGP, and many others. 186 00:06:19,500 --> 00:06:20,670 After that, we'll cover 187 00:06:20,670 --> 00:06:22,350 how route selection is going to be performed 188 00:06:22,350 --> 00:06:24,540 so that your data can be set over the most efficient route 189 00:06:24,540 --> 00:06:27,120 when it's being transferred between two different networks. 190 00:06:27,120 --> 00:06:29,790 Then, we'll discuss the concept of address translation 191 00:06:29,790 --> 00:06:33,000 by covering Static NAT, Dynamic NAT and PAT. 192 00:06:33,000 --> 00:06:35,550 Next, we'll explore some routing redundancy protocols 193 00:06:35,550 --> 00:06:37,950 and how these are used to set up a pair or a team of routers 194 00:06:37,950 --> 00:06:39,630 that are going to share a virtual IP address 195 00:06:39,630 --> 00:06:41,430 and provide load balancing or redundancy 196 00:06:41,430 --> 00:06:43,110 for our network devices. 197 00:06:43,110 --> 00:06:44,610 After that, I'm going to demonstrate 198 00:06:44,610 --> 00:06:46,740 how routers are configured for use in our networks, 199 00:06:46,740 --> 00:06:48,630 and then we'll cover multicast routing 200 00:06:48,630 --> 00:06:51,360 and how different modes of PIM are going to operate. 201 00:06:51,360 --> 00:06:52,410 Next, we'll discuss 202 00:06:52,410 --> 00:06:55,470 the Generic Routing Encapsulation protocol known as GRE 203 00:06:55,470 --> 00:06:57,690 and why it's used in some of our networks. 204 00:06:57,690 --> 00:06:59,820 Finally, we'll take a short quiz to see what you learned 205 00:06:59,820 --> 00:07:01,920 during this section of the course and review your answers 206 00:07:01,920 --> 00:07:03,600 to ensure you know why the right answers were right 207 00:07:03,600 --> 00:07:05,100 and the wrong answers were wrong. 208 00:07:05,100 --> 00:07:06,300 So if you're ready, 209 00:07:06,300 --> 00:07:07,920 let's get started with our coverage of routing 210 00:07:07,920 --> 00:07:09,420 in this section of the course.