WEBVTT 1 00:00.000 --> 00:04.600 In this video, we're going to do traditional configuration of OSPF for IPv4 2 00:04.600 --> 00:05.840 using this topology. 3 00:05.840 --> 00:09.760 So in the lab environment, which I have for you at the end of the set of videos 4 00:09.760 --> 00:09.760 , 5 00:09.760 --> 00:14.800 I've got three little virtual machines PC7 at this IP address for IPv4. 6 00:14.800 --> 00:19.280 I've got a little machine down here PC8 at this IP address and I've also got a 7 00:19.280 --> 00:20.960 little PC here PC1 8 00:20.960 --> 00:24.390 at this IP address. They're already correctly set up with their default gate 9 00:24.390 --> 00:24.800 ways. 10 00:24.800 --> 00:29.010 I also have our server one nugg, which is sitting logically on this network 11 00:29.010 --> 00:30.640 segment at .100. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 11 00:29.010 --> 00:30.640 segment at .100. 12 00:30.640 --> 00:34.800 It also has a correct default gateway and I've also got a little Windows 11 13 00:34.800 --> 00:35.840 machine that's also 14 00:35.840 --> 00:40.260 sitting up here on 10-0-1 that you can use as well. So once this is built and 15 00:40.260 --> 00:40.720 set up, 16 00:40.720 --> 00:45.300 when you do the lab, feel free to take advantage of testing and working with 17 00:45.300 --> 00:46.160 any of those devices 18 00:46.160 --> 00:50.400 connected to this infrastructure. And also notice here, I'm not including as 19 00:50.400 --> 00:52.160 part of any OSPF area, 20 00:52.160 --> 00:55.920 this serial link here, nor this one here. So let's demonstrate this 21 00:55.920 --> 00:57.920 implementation of OSPF and 22 00:57.920 --> 01:01.050 as promised at the end of this set of videos, I'll put you on a lab where you WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 22 00:57.920 --> 01:01.050 as promised at the end of this set of videos, I'll put you on a lab where you 23 01:01.050 --> 01:01.760 can get the hands on 24 01:01.760 --> 01:06.370 practice yourself. And here we go. So on the desktop in the lab environment, in 25 01:06.370 --> 01:08.000 fact, if you want to 26 01:08.000 --> 01:12.700 follow along as I do these, feel free. The link is near the bottom of this set 27 01:12.700 --> 01:13.600 of videos. 28 01:13.600 --> 01:16.480 So once again, if you don't want to wait and do the lab at the very end, you're 29 01:16.480 --> 01:17.200 welcome to join me 30 01:17.200 --> 01:21.490 and do them step by step as we do them together. So here is an icon for the lab 31 01:21.490 --> 01:22.720 topology on the desktop. 32 01:22.720 --> 01:25.540 I'm going to double click on that to open it up. And this represents our top 33 01:25.540 --> 01:26.240 ology here that we're 34 01:26.240 --> 01:30.220 going to be building. And then actually access the console for these devices. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 34 01:26.240 --> 01:30.220 going to be building. And then actually access the console for these devices. 35 01:30.220 --> 01:30.640 We're going to go 36 01:30.640 --> 01:34.990 ahead and go to server one. So server one, not only is it in the bottom right 37 01:34.990 --> 01:35.680 hand side of our 38 01:35.680 --> 01:40.230 topology, but it's also going to be used for console access to each of our rout 39 01:40.230 --> 01:41.120 ers. So I'm going to 40 01:41.120 --> 01:45.550 go ahead and double click on server one, give that a moment to initialize, and 41 01:45.550 --> 01:46.720 there it goes. And then 42 01:46.720 --> 01:50.450 I also have a little notepad document that's currently open. So this little 43 01:50.450 --> 01:51.760 document called OSPF 44 01:51.760 --> 01:56.070 configs, you can use it as a reference or you can use it to copy paste if you 45 01:56.070 --> 01:57.280 want to. If you want to 46 01:57.280 --> 02:00.360 brush up, however, when you do the lab, if you want to brush up on the commands WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 46 01:57.280 --> 02:00.360 brush up, however, when you do the lab, if you want to brush up on the commands 47 02:00.360 --> 02:01.280 , I would recommend 48 02:01.280 --> 02:05.310 doing at least a few routers manually. And then you can copy paste the rest 49 02:05.310 --> 02:06.480 just to make sure you have 50 02:06.480 --> 02:09.290 a comfort level with the commands needed to implement it. So the first thing I 51 02:09.290 --> 02:10.400 'm going to do is I'm 52 02:10.400 --> 02:14.630 going to make sure that there's no routing protocols whatsoever. In fact, there 53 02:14.630 --> 02:15.600 isn't. So I can 54 02:15.600 --> 02:18.950 actually do this. This little icon right here, that little carriage return 55 02:18.950 --> 02:19.920 symbol, if we click on 56 02:19.920 --> 02:23.430 that, here we get issue commands, we can type the commands here, and then issue 57 02:23.430 --> 02:24.240 them to multiple 58 02:24.240 --> 02:29.510 routers. So if we do a show IP protocols and press center, and then I select 59 02:29.510 --> 02:30.560 all for all routers WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 59 02:29.510 --> 02:30.560 all for all routers 60 02:30.560 --> 02:35.080 and scroll down, I don't want to send that to PC 8 PC 7 or PC 1 because they're 61 02:35.080 --> 02:35.840 not routers, 62 02:35.840 --> 02:40.480 and then click on send script, it'll send that command to all eight routers. So 63 02:40.480 --> 02:42.000 OSPF is not configured. 64 02:42.000 --> 02:46.830 So let's go back to our notepad document here. And on R1, what I'm going to do 65 02:46.830 --> 02:47.520 is simply go into 66 02:47.520 --> 02:52.130 configuration mode, start up OSPF process ID1, and that's specify auto cost 67 02:52.130 --> 02:53.760 reference bandwidth to a 68 02:53.760 --> 02:58.690 thousand, and then use this network statement net 0, 0, 0 with a wildcard bits 69 02:58.690 --> 02:59.760 all on, and assign 70 02:59.760 --> 03:04.120 any interfaces that match that network statement to area 0. So we'll just right WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 70 02:59.760 --> 03:04.120 any interfaces that match that network statement to area 0. So we'll just right 71 03:04.120 --> 03:05.680 click on that, copy, 72 03:05.680 --> 03:10.630 go to R1, and right click and paste away. And it's done. Now another thing that 73 03:10.630 --> 03:11.200 's interesting, 74 03:11.200 --> 03:14.090 and sometimes I'll do it, so I'm going to explain it now in case I do it 75 03:14.090 --> 03:15.360 accidentally. If I go into 76 03:15.360 --> 03:21.780 router OSPF1, and I say network 0, 0, 0, 0, space 0, 0, 0, 0, 0, I know those 77 03:21.780 --> 03:23.760 wildcard bits are all set to 0, 78 03:23.760 --> 03:26.920 but a long time ago, some of it Cisco said, you know what? If somebody's going 79 03:26.920 --> 03:28.240 to do that, they probably 80 03:28.240 --> 03:32.510 mean all interfaces. So even though I said all zeros there for the wildcard WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 80 03:28.240 --> 03:32.510 mean all interfaces. So even though I said all zeros there for the wildcard 81 03:32.510 --> 03:34.320 bits, if you do a do show run, 82 03:34.320 --> 03:38.970 section router, and take a look, it actually flipped them for us. So that's the 83 03:38.970 --> 03:40.000 little heads up, 84 03:40.000 --> 03:43.840 in case I ever do a four zeros for the wildcard bits, what it's really going to 85 03:43.840 --> 03:45.440 do with OSPF is flip them 86 03:45.440 --> 03:49.530 all over and just put them all as bits on. All right, so that's router one 87 03:49.530 --> 03:50.960 configured. So now we'll do a 88 03:50.960 --> 03:57.180 show IP OSPF interface brief. Now I've got four interfaces involved with OSPF. 89 03:57.180 --> 03:57.920 So on the left has the 90 03:57.920 --> 04:01.950 interface number, has a process ID, the area those interfaces are in, the IP WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 90 03:57.920 --> 04:01.950 interface number, has a process ID, the area those interfaces are in, the IP 91 04:01.950 --> 04:03.280 address associated with 92 04:03.280 --> 04:06.940 those interfaces, their cost, and their states. So you're on the left side of 93 04:06.940 --> 04:08.000 the interface, and then 94 04:08.000 --> 04:13.060 their respective process IDs are all part of OSPF process ID one, the area that 95 04:13.060 --> 04:15.040 they're all in, area zero, 96 04:15.040 --> 04:18.250 their IP address and mask that they all have, their cost. So a loopback 97 04:18.250 --> 04:19.360 interface is going to have a 98 04:19.360 --> 04:23.210 cost of one, and the other three interfaces are gigabit, and their current 99 04:23.210 --> 04:24.720 state. So all the three 100 04:24.720 --> 04:29.160 ether interfaces are acting as a DR, because there's actually no competition 101 04:29.160 --> 04:30.480 out there. As far as WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 101 04:29.160 --> 04:30.480 out there. As far as 102 04:30.480 --> 04:34.060 neighbors, the second character there, the C is for connected neighbors, 103 04:34.060 --> 04:35.280 neighbors that we see out 104 04:35.280 --> 04:39.450 there, and the first number there is the fully adjacent. So we have no 105 04:39.450 --> 04:40.880 neighbors out there, and no 106 04:40.880 --> 04:43.700 full adjacent season. That's because we haven't configured the rest of the rout 107 04:43.700 --> 04:45.200 ers yet. So let's go to 108 04:45.200 --> 04:48.900 router two, and it's a very similar treatment. So if we look at the topology 109 04:48.900 --> 04:50.320 again, router two, 110 04:50.320 --> 04:53.950 all of its interfaces are associated with area zero. So we'll go back to our 111 04:53.950 --> 04:55.120 text document. I'm going 112 04:55.120 --> 04:59.110 to grab the config here for R2, and copy that, and then make sure I'm on the 113 04:59.110 --> 05:00.240 right router R2, WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 113 04:59.110 --> 05:00.240 right router R2, 114 05:00.240 --> 05:04.580 paste away, and away we go. And then we'll go to R3. Now R3 is going to be a 115 05:04.580 --> 05:05.520 little bit different. Let's 116 05:05.520 --> 05:10.060 take a look. So here on R3, we're going to have gig one zero in area zero, fast 117 05:10.060 --> 05:11.440 -eat-at-four zero in 118 05:11.440 --> 05:15.630 area zero, but interface fast-eat-at-four slash one is going to be assigned to 119 05:15.630 --> 05:16.960 area one. So let's take 120 05:16.960 --> 05:21.050 a look at the config for R3. So for router three, we'll start the OSPF process 121 05:21.050 --> 05:22.240 one. We'll set the auto 122 05:22.240 --> 05:26.340 cost reference bandwidth to a thousand, and then I'm going to put the loopback 123 05:26.340 --> 05:27.520 interface, which is 124 05:27.520 --> 05:31.780 three dot three dot three dot three in area zero. And then I'm going to specify WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 124 05:27.520 --> 05:31.780 three dot three dot three dot three in area zero. And then I'm going to specify 125 05:31.780 --> 05:33.280 the 10 zero, anything, 126 05:33.280 --> 05:37.020 is going to be an area zero, and 10 one, anything is going to be an area one. 127 05:37.020 --> 05:37.520 Let's take a look at 128 05:37.520 --> 05:42.090 our topology once again. So this one is 10 zero, and this is 10 zero. So that 129 05:42.090 --> 05:43.120 network statement should 130 05:43.120 --> 05:47.070 put both of them in area zero, and this interface fasting at four slash one is 131 05:47.070 --> 05:48.240 10 one. So that should 132 05:48.240 --> 05:52.140 put it in area one. And then for the loopback, I just put that loopback three 133 05:52.140 --> 05:53.520 three three three into 134 05:53.520 --> 05:56.780 area zero. Although we also could have put it in area one. Normally though, I 135 05:56.780 --> 05:57.920 'll put the loopback 136 05:57.920 --> 06:02.710 in the backbone area if it's an ABR. All right, so let's go grab that config WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 136 05:57.920 --> 06:02.710 in the backbone area if it's an ABR. All right, so let's go grab that config 137 06:02.710 --> 06:03.840 copy and make sure 138 06:03.840 --> 06:08.110 on the right router are three right click. And away we go. So we do a show IP 139 06:08.110 --> 06:09.440 OSPF interface brief 140 06:09.440 --> 06:13.180 press center. I've got three interfaces in the weight state. So this one right 141 06:13.180 --> 06:14.400 here gig one zero is 142 06:14.400 --> 06:17.210 the interface that goes up to R1, and because R1 had already become the 143 06:17.210 --> 06:18.400 designated router for that 144 06:18.400 --> 06:22.230 segment and was established R3, when it saw that said, okay, you're the DR, 145 06:22.230 --> 06:23.360 there's no BDR present, 146 06:23.360 --> 06:26.160 I'll go ahead and be the BDR. And then here in just a moment, if we wait long 147 06:26.160 --> 06:27.120 enough, those three 148 06:27.120 --> 06:30.740 other interfaces should all act as DRs as well. And that's here in this column WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 148 06:27.120 --> 06:30.740 other interfaces should all act as DRs as well. And that's here in this column 149 06:30.740 --> 06:31.920 called state. So let's go 150 06:31.920 --> 06:36.190 ahead and do a up arrow key show IP OSPF interface brief. And there we go. And 151 06:36.190 --> 06:37.040 if we bring up the 152 06:37.040 --> 06:39.930 topology, let me scoot this over to the right a little bit so we can see 153 06:39.930 --> 06:41.440 everything. So let me line 154 06:41.440 --> 06:46.570 these up here on R3. F8 four slash zero is the DR for that segment. And that's 155 06:46.570 --> 06:47.440 because there's 156 06:47.440 --> 06:51.570 nobody out there yet. I haven't configured R4 yet. And that's an area zero. And 157 06:51.570 --> 06:52.480 gig one zero is an 158 06:52.480 --> 06:57.560 area zero. That's this one. And it's the BDR because R1 was already established 159 06:57.560 --> 06:59.040 DR on its gig two zero 160 06:59.040 --> 07:03.900 for that segment. And then gig zero zero not shown in our topology, but that's WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 160 06:59.040 --> 07:03.900 for that segment. And then gig zero zero not shown in our topology, but that's 161 07:03.900 --> 07:04.880 right here. That's 162 07:04.880 --> 07:08.430 acting as a designated router. And then off gig zero zero there, there's no 163 07:08.430 --> 07:10.000 neighbor. So he's all 164 07:10.000 --> 07:14.050 by himself on that segment. So he's the DR. And then F8 four slash one, which 165 07:14.050 --> 07:14.800 is right here, 166 07:14.800 --> 07:18.960 it's acting as a DR for that segment. And that's in area one again, that's four 167 07:18.960 --> 07:19.600 slash one. 168 07:19.600 --> 07:23.220 All right. So there's our three configured and we're going to follow that same 169 07:23.220 --> 07:24.880 logic as we configure 170 07:24.880 --> 07:29.170 our four and all the way down to our five, our six, our seven, and our eight. 171 07:29.170 --> 07:29.840 And here in the topology, 172 07:29.840 --> 07:33.310 I put the odd numbered routers on the left and the even numbered routers on the WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 172 07:29.840 --> 07:33.310 I put the odd numbered routers on the left and the even numbered routers on the 173 07:33.310 --> 07:34.240 right. Let's go 174 07:34.240 --> 07:37.800 back to our notepad document. Again, that notepad document is on server one. So 175 07:37.800 --> 07:39.360 we'll get into our four. 176 07:39.360 --> 07:43.130 We'll copy that. And with our four, we're going to have two of its interfaces, 177 07:43.130 --> 07:43.760 the F8 four 178 07:43.760 --> 07:48.420 slash one and gig two zero, which are both on the 10 zero address base going to 179 07:48.420 --> 07:49.920 be part of area zero. 180 07:49.920 --> 07:53.820 And then the serial three slash one that goes down to our six, that is the 181 07:53.820 --> 07:55.440 address base of 10.2. 182 07:55.440 --> 07:58.430 And that's going to become associated with area two based on our network 183 07:58.430 --> 07:58.960 statements. 184 07:58.960 --> 08:02.600 So we'll right click and make sure we go to the right router, our four and WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 184 07:58.960 --> 08:02.600 So we'll right click and make sure we go to the right router, our four and 185 08:02.600 --> 08:03.760 paste. All right. And 186 08:03.760 --> 08:08.020 there's our Json C's over to our two and also to our one. We'll continue down 187 08:08.020 --> 08:09.600 to our five. Our five 188 08:09.600 --> 08:12.950 has all of its interfaces in area one. That's on the left hand side of our top 189 08:12.950 --> 08:14.560 ology. So we'll copy that. 190 08:14.560 --> 08:18.820 Go to our five, put that in, and then we'll go to our six and grow our six 191 08:18.820 --> 08:20.320 right click copy. 192 08:20.320 --> 08:24.030 Our six is on the right hand side of our topology. All of its interfaces are in 193 08:24.030 --> 08:25.200 area two. And then 194 08:25.200 --> 08:30.930 we'll go to our seven right click copy and on our seven, go and paste that in. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 194 08:25.200 --> 08:30.930 we'll go to our seven right click copy and on our seven, go and paste that in. 195 08:30.930 --> 08:31.280 And all of its 196 08:31.280 --> 08:35.950 interfaces are in area one. And then finally our eight. So we'll grab our eight 197 08:35.950 --> 08:37.360 s config and copy. 198 08:37.360 --> 08:41.020 And all of its interfaces are in area two. So I could have just used a wild 199 08:41.020 --> 08:42.000 card, but I wanted to 200 08:42.000 --> 08:45.870 not include the serial interfaces. And that's why I'm using three network 201 08:45.870 --> 08:47.120 statements. Instead of 202 08:47.120 --> 08:51.730 using a wild card bit saying all interfaces. Also, we could go into individual 203 08:51.730 --> 08:52.720 interfaces to 204 08:52.720 --> 08:55.970 enable OSPF that way. In fact, let me go ahead and demonstrate that on one of 205 08:55.970 --> 08:57.200 the interfaces. Let's just 206 08:57.200 --> 09:02.260 grab the first two network statements and we'll go to our eight and paste that WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 206 08:57.200 --> 09:02.260 grab the first two network statements and we'll go to our eight and paste that 207 09:02.260 --> 09:03.280 in. And then 208 09:03.280 --> 09:07.930 let's do a do show IP OSPF interface brief. So the interface I don't have down 209 09:07.930 --> 09:08.640 on our eight is 210 09:08.640 --> 09:12.370 the gig zero zero. So another way of doing it is going to interface gig zero 211 09:12.370 --> 09:13.200 slash zero and 212 09:13.200 --> 09:19.170 saying IP OSPF process ID one and area two press enter. And we'll do a double 213 09:19.170 --> 09:20.320 type of end. We'll do 214 09:20.320 --> 09:25.680 the do show IP OSPF interface brief. A matter of config modes. I don't need to 215 09:25.680 --> 09:26.640 do. So I can just do 216 09:26.640 --> 09:31.680 it show IP OSPF interface brief. It'll be much better. And then we have OSPF WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 216 09:26.640 --> 09:31.680 it show IP OSPF interface brief. It'll be much better. And then we have OSPF 217 09:31.680 --> 09:32.480 enabled on those three 218 09:32.480 --> 09:37.980 interfaces loop X zero gig zero zero and F a four slash one all part of OSPF 219 09:37.980 --> 09:39.520 process ID one as shown 220 09:39.520 --> 09:44.520 right here. And all those interfaces are assigned to area two. And if we've 221 09:44.520 --> 09:45.840 given it just a minute, 222 09:45.840 --> 09:50.480 it'll also figure out that there's no other OSPS speakers on gig zero zero or 223 09:50.480 --> 09:51.440 off of gig zero zero. 224 09:51.440 --> 09:55.120 So if we hit the up to okay again, press enter. It should now be the DR for 225 09:55.120 --> 09:56.240 that segment as well. 226 09:56.240 --> 09:59.160 All right, so let's have some fun with this. Let's go to our three. That's a 227 09:59.160 --> 10:00.080 good sample. And let WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 227 09:59.160 --> 10:00.080 good sample. And let 228 10:00.080 --> 10:04.200 me scooch over the topology so we can see our three while we're configuring it. 229 10:04.200 --> 10:04.880 All right, so our 230 10:04.880 --> 10:09.080 three is right here. I also wanted to take a moment and just verify the actual 231 10:09.080 --> 10:10.320 cost of those interfaces. 232 10:10.320 --> 10:13.520 In fact, we don't have to go too far to see it. So here's our three right here. 233 10:13.520 --> 10:14.080 Oh, you know what? 234 10:14.080 --> 10:17.810 I want to let's go ahead and take a look at a router that has gigabit, fast 235 10:17.810 --> 10:18.720 ethernet, and the 236 10:18.720 --> 10:22.590 serial link associated with OSPF. So let me move the topology over just a 237 10:22.590 --> 10:24.480 little bit. All right, 238 10:24.480 --> 10:28.140 so here is our four. Let's go ahead and do the tab for our four by clicking 239 10:28.140 --> 10:29.040 right here. And here 240 10:29.040 --> 10:33.630 at our four, let's do a show IP OSPF interface brief and confirm the costs. So WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 240 10:29.040 --> 10:33.630 at our four, let's do a show IP OSPF interface brief and confirm the costs. So 241 10:33.630 --> 10:35.120 for gigabit interfaces, 242 10:35.120 --> 10:39.430 it's this cost of one. Let's just call them right here. So for gigabits, it's a 243 10:39.430 --> 10:40.640 cost of one for 244 10:40.640 --> 10:44.670 fast ethernet four slash one, it's a cost of 10. And for the serial interface 245 10:44.670 --> 10:45.360 three slash one, 246 10:45.360 --> 10:50.430 it's a cost of 15,625. And that's what we assumed earlier when we wrote that 247 10:50.430 --> 10:51.600 out in the overview. 248 10:51.600 --> 10:57.130 So let's do some basic commands to verify OSPF show IP OSPF for center. There's 249 10:57.130 --> 10:57.520 a lot of 250 10:57.520 --> 11:00.140 information here. So I'm going to hit the space bar a couple times. Let's WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 250 10:57.520 --> 11:00.140 information here. So I'm going to hit the space bar a couple times. Let's 251 11:00.140 --> 11:01.120 scroll up and take a look. 252 11:01.120 --> 11:05.350 So here's the OSPF process ID and the router ID. So the router ID is going to 253 11:05.350 --> 11:06.240 be, if it's not hard 254 11:06.240 --> 11:11.360 coded like 4444, it's going to use the highest IP address on a loopback. If you 255 11:11.360 --> 11:12.160 have no loopbacks, 256 11:12.160 --> 11:17.170 the highest IP address on another interface at the time OSPF comes up. So each 257 11:17.170 --> 11:17.920 of the routers has 258 11:17.920 --> 11:21.890 a loopback interface with the number matching the router. And that's why router 259 11:21.890 --> 11:22.640 four has a router 260 11:22.640 --> 11:27.590 ID of 4444. And as we scroll down before we get to the area information here, 261 11:27.590 --> 11:28.240 it's showing us the 262 11:28.240 --> 11:31.640 reference bandwidth is 1000 megabits per second. And that's really important. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 262 11:28.240 --> 11:31.640 reference bandwidth is 1000 megabits per second. And that's really important. 263 11:31.640 --> 11:32.640 If you have anything 264 11:32.640 --> 11:36.440 faster than fast ethernet and you want OSPF to make intelligent decisions, you 265 11:36.440 --> 11:36.960 'd want to set all 266 11:36.960 --> 11:40.910 your routers with a higher than default reference bandwidth. So we set that to 267 11:40.910 --> 11:42.080 1000. And here it's 268 11:42.080 --> 11:45.220 showing us that area zero, the backbone area is connected to. It's showing us 269 11:45.220 --> 11:46.160 the authentication 270 11:46.160 --> 11:51.010 associated with that area. And we have area two as well. Because our four also 271 11:51.010 --> 11:52.000 has an interface 272 11:52.000 --> 11:55.270 in that area. So it has one interface in that area and that is serial three 273 11:55.270 --> 11:56.560 slash one. If we go back 274 11:56.560 --> 12:02.410 up to the backbone area, it says it has four interfaces. So is that true? Let's WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 274 11:56.560 --> 12:02.410 up to the backbone area, it says it has four interfaces. So is that true? Let's 275 12:02.410 --> 12:04.080 do a show IP OSPF 276 12:04.080 --> 12:08.550 interface brief. Let's see if it has four interfaces in the backbone area. And 277 12:08.550 --> 12:10.080 it sure does. As shown 278 12:10.080 --> 12:14.240 right here, that would loopback interface, F a four slash one gig two zero, oh 279 12:14.240 --> 12:15.440 and gig zero zero, 280 12:15.440 --> 12:20.270 which isn't reflected in our topology. But indeed does have OSPF enabled on it. 281 12:20.270 --> 12:20.800 So once again, 282 12:20.800 --> 12:26.700 we do a show IP OSPF press center go down. We have four interfaces in area zero 283 12:26.700 --> 12:27.200 and we have one 284 12:27.200 --> 12:31.920 interface in area two. We could also verify who our neighbors are with show IP WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 284 12:27.200 --> 12:31.920 interface in area two. We could also verify who our neighbors are with show IP 285 12:31.920 --> 12:33.280 OSPF neighbor 286 12:33.280 --> 12:36.300 and press center. And here it's showing us we have a neighbor adjacency with 287 12:36.300 --> 12:38.400 the router idea 3333. 288 12:38.400 --> 12:45.760 That's R3 and 222. That's R2 and 6666, which is R6 off of the respective 289 12:45.760 --> 12:47.120 interfaces. 290 12:47.120 --> 12:50.040 It's also showing us here, which interfaces is a reach belong. It's also 291 12:50.040 --> 12:51.280 showing us the state. So 292 12:51.280 --> 12:57.620 this is saying here in the state column that R3 is the DR for the segment. R2 293 12:57.620 --> 12:59.440 is the DR for that segment. 294 12:59.440 --> 13:04.230 And then we have a full adjacency with no DR expected with 6666. And that's WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 294 12:59.440 --> 13:04.230 And then we have a full adjacency with no DR expected with 6666. And that's 295 13:04.230 --> 13:05.280 because it's a serial 296 13:05.280 --> 13:09.520 link point to point link. And we talked about stamp and what has to match for 297 13:09.520 --> 13:10.720 OSPF adjacencies to 298 13:10.720 --> 13:15.360 occur. So if we want to take a look, for example, at interface, fast, Ethernet, 299 13:15.360 --> 13:15.760 four slash one, 300 13:15.760 --> 13:21.320 we do a show IP OSPF interface, FAA four slash one press center. So there's our 301 13:21.320 --> 13:21.920 command that we 302 13:21.920 --> 13:26.160 issued. It says that interfaces associated with area zero. It was attached to 303 13:26.160 --> 13:27.440 via a network statement. 304 13:27.440 --> 13:32.940 It's associated with OSPF process ID one. Here's the router ID 4444. Here's the WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 304 13:27.440 --> 13:32.940 It's associated with OSPF process ID one. Here's the router ID 4444. Here's the 305 13:32.940 --> 13:34.000 network type broadcast, 306 13:34.000 --> 13:37.500 which is the default for Ethernet. It also implies that we're going to be 307 13:37.500 --> 13:38.880 looking for and using 308 13:38.880 --> 13:42.140 a designated router. And if there's two routers on that segment, a backup 309 13:42.140 --> 13:43.280 designated router, 310 13:43.280 --> 13:47.050 there's the OSPF cost based on the reference bandwidth that we set on that gig 311 13:47.050 --> 13:48.000 abit interface. 312 13:48.000 --> 13:51.710 Here it has a repeat of that cost in case we missed it the first time. It's 313 13:51.710 --> 13:52.800 also specifying here 314 13:52.800 --> 13:58.080 our state. So we are the BDR for the segment. And our three is acting as the DR 315 13:58.080 --> 13:59.280 . It's also indicating 316 13:59.280 --> 14:03.390 that here with the designated router at 3333. And we are the backup designated WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 316 13:59.280 --> 14:03.390 that here with the designated router at 3333. And we are the backup designated 317 14:03.390 --> 14:04.960 router. And here's our 318 14:04.960 --> 14:08.980 hello and dead intervals. We could also do show IP OSPF interface brief. And 319 14:08.980 --> 14:10.000 that would also confirm 320 14:10.000 --> 14:14.100 our current roles on those segments. So right there's indicating we are the BDR 321 14:14.100 --> 14:14.800 on the interface 322 14:14.800 --> 14:19.850 FAA4/1 for that segment. The show IP OSPF neighbor would indicate the roles are 323 14:19.850 --> 14:20.800 in neighbors. 324 14:20.800 --> 14:25.600 So off of our fast Ethernet 4/1 interface, our three is acting as the DR. And 325 14:25.600 --> 14:26.880 then we are acting as 326 14:26.880 --> 14:30.230 the BDR. And then the neighbor count is showing us one and one. So the second WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 326 14:26.880 --> 14:30.230 the BDR. And then the neighbor count is showing us one and one. So the second 327 14:30.230 --> 14:31.760 one there is the count. 328 14:31.760 --> 14:35.560 And the first one there is the fully adjacent. And if we want to see glimpse of 329 14:35.560 --> 14:37.040 the LSAs that are 330 14:37.040 --> 14:41.520 involved because our four is an area border router. It should have LSAs for 331 14:41.520 --> 14:43.360 area zero and also LSAs 332 14:43.360 --> 14:48.190 for area two. So we do a show IP OSPF database. That's going to give us 333 14:48.190 --> 14:50.560 information on those LSAs. 334 14:50.560 --> 14:55.160 So here's the command show IP OSPF database. Here it's starting off with the 335 14:55.160 --> 14:56.240 router link states. Those 336 14:56.240 --> 15:01.910 are the LSA type one for area zero. So our four in area zero has knowledge of WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 336 14:56.240 --> 15:01.910 are the LSA type one for area zero. So our four in area zero has knowledge of 337 15:01.910 --> 15:03.040 and is receiving 338 15:03.040 --> 15:07.890 information about the LSA type ones for all four routers that are in area zero. 339 15:07.890 --> 15:08.320 Then as we go to 340 15:08.320 --> 15:12.840 the network link states, that's the LSA type two is generated by the designated 341 15:12.840 --> 15:15.120 routers in area zero. 342 15:15.120 --> 15:18.910 So for the 12 network and the 13 network, our one based on the advertising 343 15:18.910 --> 15:20.240 router is the designated 344 15:20.240 --> 15:25.710 router. For the 24 subnet, it's router two. And for the 34 network, that is our 345 15:25.710 --> 15:26.640 three acting as 346 15:26.640 --> 15:29.740 the designated router. And one of the reasons is in that order is because I 347 15:29.740 --> 15:30.640 configured those routers WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 347 15:29.740 --> 15:30.640 configured those routers 348 15:30.640 --> 15:35.100 in that order. If we configured everything at the exact same time, they would 349 15:35.100 --> 15:36.000 duke it out based 350 15:36.000 --> 15:40.570 on priority and then the highest router ID regarding who would be the DR for a 351 15:40.570 --> 15:41.760 given segment. 352 15:41.760 --> 15:44.680 But because I did them systematically like one and two then three then four 353 15:44.680 --> 15:45.440 with some time in 354 15:45.440 --> 15:50.100 between, that's why our one went out as far as the DR functionality over our 355 15:50.100 --> 15:50.960 two for the 10, 356 15:50.960 --> 15:54.870 012 network, even though our two has a higher router ID. And then we go down a 357 15:54.870 --> 15:55.760 little bit further. 358 15:55.760 --> 15:59.440 Here are the LSA type threes, which are these summary LSAs. And these are the 359 15:59.440 --> 15:59.920 networks that are 360 15:59.920 --> 16:07.140 being advertised by the AVR. So the 555 loopbacked rests 6666, 7777, the 8888. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 360 15:59.920 --> 16:07.140 being advertised by the AVR. So the 555 loopbacked rests 6666, 7777, the 8888. 361 16:07.140 --> 16:08.240 So here are the advertising 362 16:08.240 --> 16:12.890 routers that are propagating those LSAs. So over on the left, our three is 363 16:12.890 --> 16:14.480 doing the advertisements. 364 16:14.480 --> 16:19.290 And here on our four is doing the advertisements. And then as we continue to go 365 16:19.290 --> 16:20.240 down a little further, 366 16:20.240 --> 16:24.030 it's going to repeat that process. But this time for area two. So here in area 367 16:24.030 --> 16:25.440 two, we have our LSA type 368 16:25.440 --> 16:29.340 ones from each of the routers in area two, which is our four, our six, and our 369 16:29.340 --> 16:30.880 eight. Then we have one WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 369 16:29.340 --> 16:30.880 eight. Then we have one 370 16:30.880 --> 16:35.290 designated router in area two. And that would be for the ethernet segment 371 16:35.290 --> 16:37.280 between our six and our eight. 372 16:37.280 --> 16:42.250 And based on this advertising router, our six is the DR for that segment. 373 16:42.250 --> 16:42.800 Because it is the 374 16:42.800 --> 16:46.010 advertising router. So if we popped over to our six for a moment. And here if 375 16:46.010 --> 16:47.440 we did a show IPOSPF 376 16:47.440 --> 16:53.000 interface brief, breastenter, sure enough off of its FA4/0 for that 10.2.68 377 16:53.000 --> 16:55.120 network, it is acting as the DR. 378 16:55.120 --> 17:00.810 And it also implies that our eight on its FA4/1 is acting as the BDR. We can WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 378 16:55.120 --> 17:00.810 And it also implies that our eight on its FA4/1 is acting as the BDR. We can 379 17:00.810 --> 17:01.440 verify that with the 380 17:01.440 --> 17:06.180 show IPOSPF neighbor. And then verify right there that our eight is acting as 381 17:06.180 --> 17:07.600 the BDR for that segment. 382 17:07.600 --> 17:11.750 So going back to our four, again, here's all the information for area two. So 383 17:11.750 --> 17:13.120 again, the LSA type ones 384 17:13.120 --> 17:17.140 are here for area two. The LSA type twos for area two are here. And we're going 385 17:17.140 --> 17:18.080 to have one. Also, 386 17:18.080 --> 17:22.310 what's interesting to note though is over here on our eight in area two, it has 387 17:22.310 --> 17:23.600 gig zero zero. And 388 17:23.600 --> 17:28.700 it is the DR for that. So why don't we have our eight also as a DR that's 389 17:28.700 --> 17:29.760 advertising these 390 17:29.760 --> 17:34.150 network link states for its gig zero zero address. And the answer is if there's WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 390 17:29.760 --> 17:34.150 network link states for its gig zero zero address. And the answer is if there's 391 17:34.150 --> 17:35.360 up two or more 392 17:35.360 --> 17:40.570 OSPF speakers, meaning router running OSPF on a common segment, the device that 393 17:40.570 --> 17:41.440 's the DR doesn't 394 17:41.440 --> 17:46.410 need to advertise a network link state because it's the only DR on that segment 395 17:46.410 --> 17:47.680 . It's only when you have 396 17:47.680 --> 17:52.450 two or more OSPF speakers where the DR is going to generate that network link 397 17:52.450 --> 17:53.520 state, that LSA type 398 17:53.520 --> 17:58.870 two. And that's why we only see one here for area two. And then we have the 399 17:58.870 --> 18:00.160 summary net link states WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 399 17:58.870 --> 18:00.160 summary net link states 400 18:00.160 --> 18:04.660 for area two. And those are being generated by R4. And that's why here for area 401 18:04.660 --> 18:05.600 two, the only 402 18:05.600 --> 18:11.520 advertising router is the ABR R4 that's connected to area two. So here are all 403 18:11.520 --> 18:12.480 the networks that are 404 18:12.480 --> 18:17.340 being advertised. And if we change the config and we made area two a totally 405 18:17.340 --> 18:19.120 stubby area, even these 406 18:19.120 --> 18:23.710 summary routes would be suppressed and not advertised in area two. Instead, we 407 18:23.710 --> 18:25.280 just advertise a default 408 18:25.280 --> 18:29.450 route from R4 into area two. And that would save all the routers in area two 409 18:29.450 --> 18:30.960 from having to know about WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 409 18:29.450 --> 18:30.960 from having to know about 410 18:30.960 --> 18:34.710 these detailed routes. So in our small topology, it's not a huge deal, but in a 411 18:34.710 --> 18:36.080 large network with 412 18:36.080 --> 18:40.660 hundreds of routers by quarantining off and making separate areas and making 413 18:40.660 --> 18:41.760 them stub areas, 414 18:41.760 --> 18:46.450 we can save processing power and resource utilization on those routers in those 415 18:46.450 --> 18:47.360 stub areas. 416 18:47.360 --> 18:51.870 So in fact, while we're right here, let's also go down to R8 at the bottom 417 18:51.870 --> 18:53.280 right of our topology. 418 18:53.280 --> 18:59.680 And let's do a show IP OSPF database. So R8, because it's only an area two, is 419 18:59.680 --> 19:00.240 only going to have WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 419 18:59.680 --> 19:00.240 only going to have 420 19:00.240 --> 19:05.080 information on area two. So there are the three LSA type ones coming from the 421 19:05.080 --> 19:07.200 three routers in area two. 422 19:07.200 --> 19:11.360 Here's the LSA type two coming from R6. And then we have the LSA type threes 423 19:11.360 --> 19:12.000 that are being advertised 424 19:12.000 --> 19:16.980 by the area border router. So as a quick example of how changing area two into 425 19:16.980 --> 19:18.960 a totally stubby area 426 19:18.960 --> 19:22.660 could help remove all of these summary routes and just get a default route 427 19:22.660 --> 19:23.680 being advertised by the 428 19:23.680 --> 19:27.830 ABR. What we'll do is we'll go ahead and on R4, we'll specify that area one is 429 19:27.830 --> 19:28.880 a totally stubby 430 19:28.880 --> 19:33.130 area until it not to forward summary routes into that area. So to make that WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 430 19:28.880 --> 19:33.130 area until it not to forward summary routes into that area. So to make that 431 19:33.130 --> 19:34.320 happen, we need to make 432 19:34.320 --> 19:40.110 sure that on this segment and this segment. And also this one, we'll specify 433 19:40.110 --> 19:41.920 that that area is a 434 19:41.920 --> 19:47.460 stubby area. Because if they don't agree on the type of area, that will prevent 435 19:47.460 --> 19:48.400 OSPF from neighboring 436 19:48.400 --> 19:52.440 up. So to do that, let's go to R4. And on R4, we'll go to router configuration 437 19:52.440 --> 19:53.440 mode for OSPF 438 19:53.440 --> 20:00.120 process ID1. And we'll say area two, space, question mark, stub, space question WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 438 19:53.440 --> 20:00.120 process ID1. And we'll say area two, space, question mark, stub, space question 439 20:00.120 --> 20:01.520 mark, and no summary. 440 20:01.520 --> 20:04.490 And I got to spell that out. All right. So what that effectively that does is 441 20:04.490 --> 20:06.160 tells R4 that area two 442 20:06.160 --> 20:11.140 is a stub area and not to send summary routes into that area. Now the reason we 443 20:11.140 --> 20:12.000 just lost our 444 20:12.000 --> 20:16.410 adjacency was because we have to agree with our neighbor what type of area it 445 20:16.410 --> 20:17.920 is. It's no longer 446 20:17.920 --> 20:22.730 a normal area. It's now a stub area. So let's go to R6. And here in R6, we'll 447 20:22.730 --> 20:23.440 go to configuration 448 20:23.440 --> 20:28.860 mode for router, OSPF1. And we'll say area two, stub. Now we don't have to say 449 20:28.860 --> 20:30.400 no summary here because WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 449 20:28.860 --> 20:30.400 no summary here because 450 20:30.400 --> 20:34.960 R6 is not an area border router. So it wouldn't be forwarding summaries anyway. 451 20:34.960 --> 20:35.760 If you add it here, 452 20:35.760 --> 20:39.420 it won't hurt, but it's not needed. So I'll go ahead and press enter. And you 453 20:39.420 --> 20:40.320 'll notice we lost our 454 20:40.320 --> 20:44.950 adjacency with our eight, but we did regain our adjacency with R4 because we 455 20:44.950 --> 20:46.400 now agree. So now here 456 20:46.400 --> 20:49.990 on R6, we can do a show IP OSPF. Right here is saying the number of areas in 457 20:49.990 --> 20:51.760 this router is one, 458 20:51.760 --> 20:57.490 zero normal, one stub, and zero, not so stubby areas. And right here under area 459 20:57.490 --> 20:58.640 two, it's indicating 460 20:58.640 --> 21:02.710 it's a stub area. And then we also need to go to R8 and make sure it knows as WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 460 20:58.640 --> 21:02.710 it's a stub area. And then we also need to go to R8 and make sure it knows as 461 21:02.710 --> 21:03.920 well. So on R8, 462 21:04.640 --> 21:10.790 go to configuration mode, router, OSPF1, and area two, stub. And that should 463 21:10.790 --> 21:12.560 restore our adjacency 464 21:12.560 --> 21:18.880 with R6. And there it is. Fantastic. Previously on R8, it had all of these 465 21:18.880 --> 21:20.320 summary net link states 466 21:20.320 --> 21:26.430 effectively LSA type threes with all the routes effectively advertised from R4 467 21:26.430 --> 21:26.800 regarding those 468 21:26.800 --> 21:31.050 networks. But now that we made it a stub area, and we also told R4 not to send WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 468 21:26.800 --> 21:31.050 networks. But now that we made it a stub area, and we also told R4 not to send 469 21:31.050 --> 21:31.920 the summaries, 470 21:31.920 --> 21:35.280 check it out. Now if we hit the app, or I'll key a few times, and do that same 471 21:35.280 --> 21:36.000 exact command show 472 21:36.000 --> 21:41.180 IP OSPF database in press center. Look at this. We still have the LSA type ones 473 21:41.180 --> 21:41.920 for our four, 474 21:41.920 --> 21:48.390 our six, and our eight. We still have the DR thus advertising the LSA type two, 475 21:48.390 --> 21:49.360 but check this out. 476 21:49.360 --> 21:53.010 For the summary net link states, we only have one. And that's advertising the 477 21:53.010 --> 21:54.160 default route. So if 478 21:54.160 --> 21:57.690 we looked at the routing table, it is show IP route press center, you'll notice 479 21:57.690 --> 21:58.640 . In fact, let's do it 480 21:58.640 --> 22:03.360 again with a OSPF. We'll filter it down. So we have a default route that's been WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 480 21:58.640 --> 22:03.360 again with a OSPF. We'll filter it down. So we have a default route that's been 481 22:03.360 --> 22:04.080 advertised. 482 22:04.080 --> 22:08.820 Then we have an OSPF learned route. That's R6's loopback. That's an area two. 483 22:08.820 --> 22:10.800 We have 10246, 484 22:10.800 --> 22:19.010 which is the network between R6 and R4. What the heck is 1026? Why do we have 485 22:19.010 --> 22:21.360 1026? I'm curious. 486 22:21.360 --> 22:26.670 Who's got 1026? Let's go take a look at R6. That's not an R2. It's show IP 487 22:26.670 --> 22:28.000 interface brief. 488 22:28.000 --> 22:34.090 I see. So R6 has a 1026 interface. And we do show IP OSPF interface brief. Sure WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 488 22:28.000 --> 22:34.090 I see. So R6 has a 1026 interface. And we do show IP OSPF interface brief. Sure 489 22:34.090 --> 22:34.480 enough, 490 22:34.480 --> 22:39.280 it's enabled for OSPF. And that's why we know about it. So let's go back down 491 22:39.280 --> 22:40.080 to R8. 492 22:40.080 --> 22:43.740 I was just curious. Where does that come from? So by turning this area, area 493 22:43.740 --> 22:45.120 two into a stub area, 494 22:45.120 --> 22:49.890 and also telling our four to go ahead and not send LSA type threes into that 495 22:49.890 --> 22:50.320 area, 496 22:50.320 --> 22:54.320 we're reducing the size of the routing tables on routers in area two, including 497 22:54.320 --> 22:56.160 R6 and R8. And 498 22:56.160 --> 22:59.920 just as a quick test, if we want to verify full connectivity, we could go ahead 499 22:59.920 --> 23:00.880 and try to ping, WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 499 22:59.920 --> 23:00.880 and try to ping, 500 23:00.880 --> 23:08.080 for example, it's ping from R8 all the way to this PC7 at 10.1.7.10. So back at 501 23:08.080 --> 23:08.960 R8, let's go ahead and 502 23:08.960 --> 23:14.040 do a ping to 10.1.7.10. And that's working. Let's also do a trace just to 503 23:14.040 --> 23:17.040 verify the path 10.1.7.10. 504 23:17.040 --> 23:22.560 And then based on the trace, the next top was R6, and then R4, and then R2, and 505 23:22.560 --> 23:23.600 then R1, 506 23:23.600 --> 23:28.670 and then R3, and then R5, and then R7, to finally hit the destination, which 507 23:28.670 --> 23:29.840 was at .10. 508 23:29.840 --> 23:33.680 So now that we have the opportunity to see the legacy implementation of IPv4 WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 508 23:29.840 --> 23:33.680 So now that we have the opportunity to see the legacy implementation of IPv4 509 23:33.680 --> 23:34.720 with OSPF, 510 23:34.720 --> 23:39.100 in the next video, I like to walk you through the legacy implementation of OSPF 511 23:39.100 --> 23:40.000 , but this time for 512 23:40.000 --> 23:43.900 IPv6. So a lot of the same concepts are going to hold true, except the IP 513 23:43.900 --> 23:45.440 addresses are a lot longer. 514 23:45.440 --> 23:47.360 So I'll see you in the next video when you're ready.