WEBVTT 1 00:00.000 --> 00:05.400 I thought I'd start off this lab demo by taking a look at what happens when we 2 00:05.400 --> 00:05.700 enable 3 00:05.700 --> 00:09.480 too many VLANs on a traditional catalyst switch. 4 00:09.480 --> 00:13.020 So this is a catalyst 9K, not even like an ancient switch. 5 00:13.020 --> 00:17.440 This is a modern Cisco catalyst 9K switch, and we're going to find it only 6 00:17.440 --> 00:19.200 supports 128 7 00:19.200 --> 00:21.080 STP instances. 8 00:21.080 --> 00:26.750 So if I do a show spanning tree, I can see here, we're only running a single V 9 00:26.750 --> 00:27.200 LAN at 10 00:27.200 --> 00:32.480 the moment, so we're running rapid PVST plus if I do a show VLAN, we see we're WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 10 00:27.200 --> 00:32.480 the moment, so we're running rapid PVST plus if I do a show VLAN, we see we're 11 00:32.480 --> 00:32.960 only running 12 00:32.960 --> 00:37.600 one VLAN, I can do a show interface trunk, and see that we have all of the VLAN 13 00:37.600 --> 00:38.320 s enabled 14 00:38.320 --> 00:41.240 but we're only one configured, so far no problem. 15 00:41.240 --> 00:45.760 I could configure VLAN 10, VLAN 20, I could configure 100 VLANs. 16 00:45.760 --> 00:52.030 But if I were to do a config T here and create more than 128 VLANs, let's say I 17 00:52.030 --> 00:52.960 configure 18 00:52.960 --> 00:59.320 150 VLANs, exit out, sometimes we'll get an error message here, and sometimes 19 00:59.320 --> 01:00.000 we won't WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 19 00:59.320 --> 01:00.000 we won't 20 01:00.000 --> 01:02.960 look like we're not going to get one this time, but here's the problem. 21 01:02.960 --> 01:07.550 If I do a show spanning tree, so I'm going to see that I've got an instance for 22 01:07.550 --> 01:07.960 VLAN 23 01:07.960 --> 01:12.730 1 and an instance for VLAN 2 when an instance for VLAN 3 and so on and so forth 24 01:12.730 --> 01:12.760 . 25 01:12.760 --> 01:17.960 So if I look at VLAN 128, we're good, we've got an instance for 128. 26 01:17.960 --> 01:23.640 If I look at 129, it doesn't exist, that is a big concern. 27 01:23.640 --> 01:30.440 So if I do a show interface trunk, we're going to find that we do have all VLAN WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 27 01:23.640 --> 01:30.440 So if I do a show interface trunk, we're going to find that we do have all VLAN 28 01:30.440 --> 01:31.600 s on 1 through 29 01:31.600 --> 01:33.240 150 allowed. 30 01:33.240 --> 01:40.650 So we're allowing the VLANs and yet we are not running spanning tree protocol 31 01:40.650 --> 01:41.520 across that 32 01:41.520 --> 01:42.760 link for those VLANs. 33 01:42.760 --> 01:46.120 So this is a potential disaster waiting to happen. 34 01:46.120 --> 01:50.850 We have to be absolutely certain that we are running as many spanning tree 35 01:50.850 --> 01:51.760 instances as 36 01:51.760 --> 01:56.000 we have VLANs in a rapid PVST plus environment. 37 01:56.000 --> 02:00.410 So if this was our production network and we had 150 VLANs, we would absolutely WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 37 01:56.000 --> 02:00.410 So if this was our production network and we had 150 VLANs, we would absolutely 38 02:00.410 --> 02:00.760 have 39 02:00.760 --> 02:04.040 no choice but to switch over to MST. 40 02:04.040 --> 02:05.920 So let's flip over to our lab environment. 41 02:05.920 --> 02:08.720 This is the lab environment that you're going to have access to. 42 02:08.720 --> 02:12.490 It involves virtual switches and these virtual switches don't run out of 43 02:12.490 --> 02:14.120 spanning tree topologies, 44 02:14.120 --> 02:17.210 which is kind of nice but we couldn't actually demonstrate it on these, which 45 02:17.210 --> 02:18.200 is why I demonstrated 46 02:18.200 --> 02:19.920 it on real hardware. 47 02:19.920 --> 02:24.840 So we're going to go about this looking at MST configuration. 48 02:24.840 --> 02:26.280 Let's pull up the topology here. 49 02:26.280 --> 02:29.440 What we're going to do is we're going to do a three step plan. 50 02:29.440 --> 02:34.640 First of all, we're going to activate MST. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 50 02:29.440 --> 02:34.640 First of all, we're going to activate MST. 51 02:34.640 --> 02:39.980 Second of all, we are going to do our MST configuration and we're actually 52 02:39.980 --> 02:40.960 going to focus 53 02:40.960 --> 02:45.190 on the first two, we're going to get our name for our region as well as our 54 02:45.190 --> 02:48.040 revision number. 55 02:48.040 --> 02:55.050 And then the third step here is simply getting our VLAN to instance mapping set 56 02:55.050 --> 02:55.120 . 57 02:55.120 --> 03:00.380 And as we've said, we need to match this on all of these switches in our top WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 57 02:55.120 --> 03:00.380 And as we've said, we need to match this on all of these switches in our top 58 03:00.380 --> 03:01.160 ology. 59 03:01.160 --> 03:06.130 Otherwise we're going to create a fragmented MST domain by creating multiple 60 03:06.130 --> 03:07.000 regions. 61 03:07.000 --> 03:10.760 Now after all of this, we're going to go ahead and do a fourth set of 62 03:10.760 --> 03:11.840 configurations just 63 03:11.840 --> 03:16.880 to look at the optional parameters such as priority costs, timers. 64 03:16.880 --> 03:20.520 We'll take a look at that because we'll need to know how to tune that. 65 03:20.520 --> 03:26.270 But at the same time, our focus for configuring MST will simply be these three 66 03:26.270 --> 03:27.200 steps. 67 03:27.200 --> 03:30.480 So let's switch over to the lab and we'll start on switch three. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 67 03:27.200 --> 03:30.480 So let's switch over to the lab and we'll start on switch three. 68 03:30.480 --> 03:33.240 So again, according to our plan, we're going to activate MST. 69 03:33.240 --> 03:37.010 The way we do that is get into global configuration and simply say spanning 70 03:37.010 --> 03:38.160 tree mode, which is 71 03:38.160 --> 03:43.000 the same command we use to activate rapid pvst and we say MST here and head 72 03:43.000 --> 03:43.760 enter. 73 03:43.760 --> 03:48.040 At this point, if I do a show spanning tree, we're going to see that spanning 74 03:48.040 --> 03:49.040 tree is enabled 75 03:49.040 --> 03:50.840 for MSTP. 76 03:50.840 --> 03:53.960 So yeah, most of Cisco syntax involves MST. 77 03:53.960 --> 03:58.000 Every now and again, we will see MSTP with the P added there at the end. 78 03:58.000 --> 04:03.040 But notice over here where we'd normally see a VLAN ID, we see this MST zero. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 78 03:58.000 --> 04:03.040 But notice over here where we'd normally see a VLAN ID, we see this MST zero. 79 04:03.040 --> 04:06.620 Well, as we've mentioned, zero is the default instance and this is 80 04:06.620 --> 04:07.960 representative of that 81 04:07.960 --> 04:09.320 instance now. 82 04:09.320 --> 04:12.760 This command looks pretty similar to our pvst plus command. 83 04:12.760 --> 04:15.840 In fact, a lot of commands are going to feel very similar. 84 04:15.840 --> 04:19.880 We're simply swapping out the VLAN ID for an instance. 85 04:19.880 --> 04:23.600 We'll see that when our show commands as well as our configuration commands. 86 04:23.600 --> 04:28.280 So in this case, instant zero shows that we have a couple of interfaces here. 87 04:28.280 --> 04:30.160 They were in blocking when I looked at it. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 87 04:28.280 --> 04:30.160 They were in blocking when I looked at it. 88 04:30.160 --> 04:31.960 Let's just run this one more time. 89 04:31.960 --> 04:34.880 And now we see that we're in affording state. 90 04:34.880 --> 04:38.580 Now if we see this boundary, this is what we're we talked about earlier is 91 04:38.580 --> 04:39.120 having a 92 04:39.120 --> 04:41.600 boundary out this interface. 93 04:41.600 --> 04:43.600 And in parentheses, it mentions STP. 94 04:43.600 --> 04:47.680 That's because we're interfacing with a switch running pvst plus. 95 04:47.680 --> 04:51.760 And so it's letting us know that there's not an MST switch on the other side. 96 04:51.760 --> 04:54.360 So no worries, we'll sync all of this up. 97 04:54.360 --> 04:58.160 But let's just go ahead and continue through our strategy here. 98 04:58.160 --> 05:02.120 Oh, and by the way, if we do a show VLAN on this, we're going to find only VLAN WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 98 04:58.160 --> 05:02.120 Oh, and by the way, if we do a show VLAN on this, we're going to find only VLAN 99 05:02.120 --> 05:02.280 one is 100 05:02.280 --> 05:03.880 configured. 101 05:03.880 --> 05:06.280 So let's go ahead and configure some VLANs. 102 05:06.280 --> 05:10.080 I'm going to add the lens two through 10 to the configuration. 103 05:10.080 --> 05:14.260 And now we'll get on with our plan here that we wanted to then move into MST 104 05:14.260 --> 05:15.400 configuration. 105 05:15.400 --> 05:19.800 Well, the way we do that is by entering into a configuration mode. 106 05:19.800 --> 05:23.400 So I do spanning tree MST configuration and hit enter. 107 05:23.400 --> 05:26.960 And we'll notice now we're in a special MST config set. 108 05:26.960 --> 05:30.240 So this is where we're going to perform the rest of our configuration. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 108 05:26.960 --> 05:30.240 So this is where we're going to perform the rest of our configuration. 109 05:30.240 --> 05:32.080 I'm going to start by giving it a name. 110 05:32.080 --> 05:33.080 This is that region name. 111 05:33.080 --> 05:36.360 I'll just call this CBTN for right now. 112 05:36.360 --> 05:39.120 And then when I run a question, Mark will see the other options. 113 05:39.120 --> 05:44.400 So for example, revision, I can set the revision ID here and our configuration 114 05:44.400 --> 05:45.400 revision number 115 05:45.400 --> 05:46.400 rather. 116 05:46.400 --> 05:49.520 And we see that that can be between zero and 65, 535. 117 05:49.520 --> 05:52.560 I'll just set this as a revision one. 118 05:52.560 --> 05:56.600 And these again have to match every across all the switches. 119 05:56.600 --> 05:59.200 If we want it to be a continuous region. 120 05:59.200 --> 06:04.760 So from here, now we need to create our instances along with our VLAN mappings. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 120 05:59.200 --> 06:04.760 So from here, now we need to create our instances along with our VLAN mappings. 121 06:04.760 --> 06:10.300 Remember, instant zero is going to be the default as well as the catch point 122 06:10.300 --> 06:10.840 for all 123 06:10.840 --> 06:11.840 of the VLANs. 124 06:11.840 --> 06:15.120 So right now all of the VLANs are part of instance zero. 125 06:15.120 --> 06:16.280 Let's say I want to split them up. 126 06:16.280 --> 06:19.880 I want to put the odds in instance one and the evens and instance two. 127 06:19.880 --> 06:20.920 Let's do that. 128 06:20.920 --> 06:24.040 And so I'm going to move all of those VLANs one through 10 into one of the 129 06:24.040 --> 06:25.640 other two instances. 130 06:25.640 --> 06:29.200 But keep in mind, if I add a VLAN later, it's going to still land an instance 131 06:29.200 --> 06:29.760 zero even 132 06:29.760 --> 06:32.870 though I'm not actually using it, which is actually a good way to do it in WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 132 06:29.760 --> 06:32.870 though I'm not actually using it, which is actually a good way to do it in 133 06:32.870 --> 06:33.680 production. 134 06:33.680 --> 06:36.640 It means I don't accidentally add VLANs into topologies. 135 06:36.640 --> 06:38.440 I have to be intentional with it. 136 06:38.440 --> 06:40.280 The command for this is going to be instance. 137 06:40.280 --> 06:42.120 So I'm going to say instance and then my ID. 138 06:42.120 --> 06:46.040 So in this case one and then VLAN and I specify the VLANs. 139 06:46.040 --> 06:48.960 So I said I wanted the odds in here. 140 06:48.960 --> 06:51.320 That should be one three five seven nine. 141 06:51.320 --> 06:58.740 And then I'll hit enter and do instance two with VLANs two four six eight and 142 06:58.740 --> 06:58.880 ten. 143 06:58.880 --> 06:59.880 And there we go. 144 06:59.880 --> 07:02.880 I've created my VLAN to instance mapping. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 144 06:59.880 --> 07:02.880 I've created my VLAN to instance mapping. 145 07:02.880 --> 07:04.360 And so that's it. 146 07:04.360 --> 07:07.410 That's all we have to do to get MST up and running other than the fact that we 147 07:07.410 --> 07:07.760 have to 148 07:07.760 --> 07:10.400 do this on the other switches. 149 07:10.400 --> 07:14.490 So let's go ahead and log in and do that real quick to switch four and switch 150 07:14.490 --> 07:15.000 five. 151 07:15.000 --> 07:17.200 Let's just review this real quick. 152 07:17.200 --> 07:20.680 Spanning tree mode MST that gets us running. 153 07:20.680 --> 07:27.170 And then we enter into the spanning tree MST configuration sub configuration 154 07:27.170 --> 07:27.320 prompt. 155 07:27.320 --> 07:33.560 And now I can do the other commands such as name CBTN revision one. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 155 07:27.320 --> 07:33.560 And now I can do the other commands such as name CBTN revision one. 156 07:33.560 --> 07:35.200 And now I have to do those instances. 157 07:35.200 --> 07:37.360 So I could actually just copy those. 158 07:37.360 --> 07:38.720 Let's go grab that. 159 07:38.720 --> 07:41.400 So I'll grab instance one instance to configuration. 160 07:41.400 --> 07:46.530 This will make sure that I don't do the wrong configuration and that we're all 161 07:46.530 --> 07:47.360 synced up. 162 07:47.360 --> 07:49.160 Now let's do it one more time on switch five. 163 07:49.160 --> 07:52.320 Just shows though how quick this actually is. 164 07:52.320 --> 08:00.920 Spanning tree mode MST spanning tree MST configuration name CBTN revision one. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 164 07:52.320 --> 08:00.920 Spanning tree mode MST spanning tree MST configuration name CBTN revision one. 165 08:00.920 --> 08:06.270 And then I paste in my instance of VLAN mapping and MST sometimes could feel 166 08:06.270 --> 08:07.280 like it's more 167 08:07.280 --> 08:08.280 complex. 168 08:08.280 --> 08:09.280 It's more complex. 169 08:09.280 --> 08:10.640 There's more to do just objectively. 170 08:10.640 --> 08:12.240 I have to enter these commands. 171 08:12.240 --> 08:16.080 But look at what I just did one, two, three, four, five, six lines to configure 172 08:16.080 --> 08:16.880 two instances 173 08:16.880 --> 08:18.120 in a bunch of VLANs. 174 08:18.120 --> 08:19.560 That's not that bad. 175 08:19.560 --> 08:21.680 MST can feel intimidating at times. 176 08:21.680 --> 08:25.380 But really it just boils down to these commands and then naturally moving 177 08:25.380 --> 08:26.240 forward any of the 178 08:26.240 --> 08:31.550 other commands I would be entering for rapid PVST plus I just swap out MST for WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 178 08:26.240 --> 08:31.550 other commands I would be entering for rapid PVST plus I just swap out MST for 179 08:31.550 --> 08:32.240 VLAN. 180 08:32.240 --> 08:34.640 So let's take a look at a few examples here. 181 08:34.640 --> 08:36.920 So first and foremost, let's make sure that we're up and running. 182 08:36.920 --> 08:41.360 If I do a show spanning tree, I should see I'm running in MST mode. 183 08:41.360 --> 08:44.240 I no longer see anything about boundaries out here. 184 08:44.240 --> 08:48.160 Granted I'm on a different switch, but we'll go confirm that in the other 185 08:48.160 --> 08:49.480 switches as well. 186 08:49.480 --> 08:52.040 Now we have more information running here. 187 08:52.040 --> 08:54.560 So we've got MST zero and MST one. 188 08:54.560 --> 08:56.040 Now where's MST two? 189 08:56.040 --> 08:58.040 Well, where would it be? 190 08:58.040 --> 08:59.040 What did we do? 191 08:59.040 --> 09:02.600 We put all of these VLANs into MST two. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 191 08:59.040 --> 09:02.600 We put all of these VLANs into MST two. 192 09:02.600 --> 09:06.720 And remember I in the first switch I actually had to configure all the VLANs. 193 09:06.720 --> 09:08.480 Yeah, I haven't actually done that yet. 194 09:08.480 --> 09:12.800 So only VLAN one is running on the switch, which means by default only instance 195 09:12.800 --> 09:13.240 one is 196 09:13.240 --> 09:14.880 running on the switch. 197 09:14.880 --> 09:21.160 So let's go ahead and configure some VLANs, VLAN two through ten. 198 09:21.160 --> 09:22.720 And then show spanning tree again. 199 09:22.720 --> 09:25.000 And now we should see zero. 200 09:25.000 --> 09:26.320 We'll always be there. 201 09:26.320 --> 09:28.360 And then one and two. 202 09:28.360 --> 09:29.360 But that's it. 203 09:29.360 --> 09:34.320 I don't have ten different VLANs or ten different topologies listed here. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 203 09:29.360 --> 09:34.320 I don't have ten different VLANs or ten different topologies listed here. 204 09:34.320 --> 09:37.520 I have one topology for instance one. 205 09:37.520 --> 09:39.640 I have one topology for instance two. 206 09:39.640 --> 09:42.630 And then I do have instance zero always still running, even though we don't 207 09:42.630 --> 09:43.240 actually have 208 09:43.240 --> 09:45.880 any VLANs associated with it. 209 09:45.880 --> 09:49.280 So let's go ahead and go to switch four. 210 09:49.280 --> 09:52.000 Did not configure the VLANs here either. 211 09:52.000 --> 09:53.360 So we'll get that up and running. 212 09:53.360 --> 09:57.660 And then let's go back to switch three and do our show spanning tree to confirm 213 09:57.660 --> 09:58.000 that 214 09:58.000 --> 10:00.760 it doesn't see any boundary ports anymore. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 214 09:58.000 --> 10:00.760 it doesn't see any boundary ports anymore. 215 10:00.760 --> 10:02.240 And indeed it does not. 216 10:02.240 --> 10:06.840 So we've got all of our instances running over here as well. 217 10:06.840 --> 10:09.600 Now there is another really good command that we should run at this point, 218 10:09.600 --> 10:10.120 which is show 219 10:10.120 --> 10:12.920 spanning tree MST configuration. 220 10:12.920 --> 10:16.720 If we run this command, we're going to see the instance to VLAN mapping. 221 10:16.720 --> 10:19.680 This is very important that we can confirm that the VLANs are appropriately 222 10:19.680 --> 10:20.120 mapped to 223 10:20.120 --> 10:21.460 our instances. 224 10:21.460 --> 10:25.130 And again, if I were to get on here and add VLAN 11, it would land an instance 225 10:25.130 --> 10:25.680 zero by 226 10:25.680 --> 10:26.680 default. 227 10:26.680 --> 10:31.970 We can always land in zero unless we have pre-configured it essentially to land WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 227 10:26.680 --> 10:31.970 We can always land in zero unless we have pre-configured it essentially to land 228 10:31.970 --> 10:32.280 in a 229 10:32.280 --> 10:34.360 different instance. 230 10:34.360 --> 10:35.840 So our plan is done. 231 10:35.840 --> 10:38.470 We've done our three steps, but let's go ahead and do some optional 232 10:38.470 --> 10:39.360 configurations, 233 10:39.360 --> 10:40.360 so to speak. 234 10:40.360 --> 10:43.400 Optional in the lab really required for production. 235 10:43.400 --> 10:48.710 So if I do a config T here, we'll find that I can go ahead and well, let's 236 10:48.710 --> 10:49.680 actually let's 237 10:49.680 --> 10:51.400 make switch three the root. 238 10:51.400 --> 10:56.360 So if I was doing this with per VLAN spanning tree, I'd say spanning tree, VLAN 239 10:56.360 --> 10:57.080 one, and 240 10:57.080 --> 10:59.520 then we'd configure priority. 241 10:59.520 --> 11:03.680 But I can't actually do that with MST because VLAN one doesn't have its own top WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 241 10:59.520 --> 11:03.680 But I can't actually do that with MST because VLAN one doesn't have its own top 242 11:03.680 --> 11:04.360 ology. 243 11:04.360 --> 11:08.680 So instead, I'm going to say spanning tree MST. 244 11:08.680 --> 11:12.820 And so at this point, I could say MST one question mark, and then I also get 245 11:12.820 --> 11:13.520 priority 246 11:13.520 --> 11:14.640 ability. 247 11:14.640 --> 11:17.240 And by the way, we'll notice that we can use those root macro. 248 11:17.240 --> 11:19.000 So it's nice to have both of those. 249 11:19.000 --> 11:22.400 But if I want to set switch three to be the root, I can say priority zero or 250 11:22.400 --> 11:23.000 priority 251 11:23.000 --> 11:29.830 4096, maybe for switch three for MST one, and then maybe for MST two, I want to 252 11:29.830 --> 11:30.360 run this WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 252 11:29.830 --> 11:30.360 run this 253 11:30.360 --> 11:31.360 as the backup route. 254 11:31.360 --> 11:33.960 So 81, I did that wrong. 255 11:33.960 --> 11:40.000 81 92 for MST two, and then go to switch four and do the same thing in reverse. 256 11:40.000 --> 11:46.600 So switch four would be spanning tree MST one priority 81 92. 257 11:46.600 --> 11:51.160 And then MST two priority 4096. 258 11:51.160 --> 11:57.110 So now if I look at things from switch five's perspective, show spanning tree 259 11:57.110 --> 11:57.840 zero again, 260 11:57.840 --> 11:58.840 we're not really using. 261 11:58.840 --> 12:00.040 So we'll skip past that. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 261 11:58.840 --> 12:00.040 So we'll skip past that. 262 12:00.040 --> 12:02.320 For one, we said that switch three was the root. 263 12:02.320 --> 12:05.120 So the link to switch three is an affording state. 264 12:05.120 --> 12:09.880 The link to switch four is in a blocking state and switch or MST two should be 265 12:09.880 --> 12:10.320 flipped 266 12:10.320 --> 12:11.320 of that. 267 12:11.320 --> 12:12.680 And we can see it's still here on the screen. 268 12:12.680 --> 12:18.160 So yes, block first onto one and then forwarding on three slash one. 269 12:18.160 --> 12:19.160 So that's like that. 270 12:19.160 --> 12:24.250 We configured our two priorities and everything feels very similar to rapid per 271 12:24.250 --> 12:25.240 VLAN spanning 272 12:25.240 --> 12:26.800 tree at this point. 273 12:26.800 --> 12:28.280 So what else could we do? 274 12:28.280 --> 12:29.840 Well we could configure some timers. 275 12:29.840 --> 12:31.720 So I go back to switch three here. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 275 12:29.840 --> 12:31.720 So I go back to switch three here. 276 12:31.720 --> 12:35.570 And when we ran that question mark command spanning tree MST one question mark, 277 12:35.570 --> 12:35.800 notice 278 12:35.800 --> 12:39.040 it doesn't have all of these timers. 279 12:39.040 --> 12:44.440 When I ran this for VLAN with the VLAN in the command, it had all the timer 280 12:44.440 --> 12:45.400 options. 281 12:45.400 --> 12:49.360 That's because Cisco allows us to change timers on a per topology basis, 282 12:49.360 --> 12:50.240 basically per 283 12:50.240 --> 12:51.480 VLAN. 284 12:51.480 --> 12:56.820 Well in MST we mentioned we can't configure timers as part of an individual 285 12:56.820 --> 12:57.880 instance. 286 12:57.880 --> 13:00.840 Instead this must be done globally for all instances. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 286 12:57.880 --> 13:00.840 Instead this must be done globally for all instances. 287 13:00.840 --> 13:02.880 And so we see the timers set here. 288 13:02.880 --> 13:08.080 I would do spanning tree MST and then my three different timer options. 289 13:08.080 --> 13:11.780 And then lastly from like a cost perspective, if I wanted to get onto an 290 13:11.780 --> 13:12.880 interface, let's 291 13:12.880 --> 13:19.560 say interface gig one slash zero here, I can do a spanning tree cost. 292 13:19.560 --> 13:23.200 And maybe I would just do spanning tree cost a thousand. 293 13:23.200 --> 13:28.800 But then I can also say spanning tree MST one and then set a different cost. 294 13:28.800 --> 13:35.630 So this cost, just like with our PVST plus configuration is going to apply to M WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 294 13:28.800 --> 13:35.630 So this cost, just like with our PVST plus configuration is going to apply to M 295 13:35.630 --> 13:36.400 ST one, 296 13:36.400 --> 13:40.000 whereas this is going to apply to all of the other instances. 297 13:40.000 --> 13:47.570 So if I do a show spanning tree, we're going to find that MST zero now has the 298 13:47.570 --> 13:48.680 thousand, 299 13:48.680 --> 13:51.000 but MST one has a hundred. 300 13:51.000 --> 13:56.470 And then MST two is back to a thousand, which exactly matches the configuration 301 13:56.470 --> 13:56.520 . 302 13:56.520 --> 14:01.110 So there's a lot of things to think about with MST I suppose, but it really WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 302 13:56.520 --> 14:01.110 So there's a lot of things to think about with MST I suppose, but it really 303 14:01.110 --> 14:01.840 just comes 304 14:01.840 --> 14:06.480 back to making sure those initial configurations are in the right place. 305 14:06.480 --> 14:10.940 We want to make sure that we've got those three configurations, especially the 306 14:10.940 --> 14:11.200 region 307 14:11.200 --> 14:17.100 name, the revision ID, revision number, as well as the instance to VLAN mapping 308 14:17.100 --> 14:17.440 . 309 14:17.440 --> 14:20.680 If all of those are good, then we're in good shape. 310 14:20.680 --> 14:25.240 If I were to, for example, get on here and say spanning tree MST config and I 311 14:25.240 --> 14:26.080 do revision 312 14:26.080 --> 14:27.560 two. 313 14:27.560 --> 14:32.120 Well, now I've changed just that one little parameter on one of the switches. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 313 14:27.560 --> 14:32.120 Well, now I've changed just that one little parameter on one of the switches. 314 14:32.120 --> 14:36.160 And if I do a show spanning tree, they're now going to think that they're all 315 14:36.160 --> 14:36.720 part of 316 14:36.720 --> 14:38.680 different instances. 317 14:38.680 --> 14:41.320 So we're going to have to wait for a few moments for this to sync. 318 14:41.320 --> 14:46.120 So let's do that. 319 14:46.120 --> 14:47.120 But here we go. 320 14:47.120 --> 14:50.360 It has started to synchronize and we do see now that there's a boundary here. 321 14:50.360 --> 14:51.960 We are running rapid on the other side. 322 14:51.960 --> 14:55.750 Again, MST runs rapid under the hood, but now we believe that we have a 323 14:55.750 --> 14:56.600 boundary link 324 14:56.600 --> 15:00.760 to a different domain, a different spanning tree region because I changed just WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 324 14:56.600 --> 15:00.760 to a different domain, a different spanning tree region because I changed just 325 15:00.760 --> 15:01.320 that one 326 15:01.320 --> 15:02.320 little parameter. 327 15:02.320 --> 15:03.800 So that's why it's so important. 328 15:03.800 --> 15:08.350 We have all three parameters synchronized on all of the switches in our 329 15:08.350 --> 15:09.440 environment, 330 15:09.440 --> 15:11.840 and that will create one uniform domain. 331 15:11.840 --> 15:14.360 And at that point, it's going to feel a whole lot like rapid pervieland 332 15:14.360 --> 15:15.080 spanning tree.