WEBVTT 1 00:00.000 --> 00:06.400 Now, MST configuration is going to require a little bit more effort up front 2 00:06.400 --> 00:07.220 than we would 3 00:07.220 --> 00:12.880 require with RapidPVST+ which might be another barrier to deploying MST, but it 4 00:12.880 --> 00:13.360 really comes 5 00:13.360 --> 00:18.170 down to the configuration of what we refer to as the attributes of the 6 00:18.170 --> 00:19.400 environment. 7 00:19.400 --> 00:24.890 Unlike RapidPVST+ as well as common spanning tree, we are going to have 8 00:24.890 --> 00:26.240 switches that are 9 00:26.240 --> 00:31.070 going to be sending information inside of the BPDUs to make sure that we all WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 9 00:26.240 --> 00:31.070 going to be sending information inside of the BPDUs to make sure that we all 10 00:31.070 --> 00:31.760 agree on the 11 00:31.760 --> 00:35.820 configuration of the spanning tree environment. So we didn't really have 12 00:35.820 --> 00:36.880 attributes like that 13 00:36.880 --> 00:43.200 with legacy or maybe RapidSpanningTree types of environments and yet with MST 14 00:43.200 --> 00:43.680 we're going 15 00:43.680 --> 00:50.560 to have some of those. The first attribute is known as the region name. This is 16 00:50.560 --> 00:50.880 intended 17 00:50.880 --> 00:56.070 to make sure that if we have, let's say, a network on the left and a network on 18 00:56.070 --> 00:57.840 the right and we've 19 00:57.840 --> 01:02.150 got maybe a merger or something along those lines or we just want to keep these WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 19 00:57.840 --> 01:02.150 got maybe a merger or something along those lines or we just want to keep these 20 01:02.150 --> 01:03.200 layer to network 21 01:03.200 --> 01:07.990 separated from a spanning tree perspective, each one of these can have its own 22 01:07.990 --> 01:08.800 region name. 23 01:08.800 --> 01:13.240 And this will make it so that we don't have to align with all of the other 24 01:13.240 --> 01:14.720 properties. We might 25 01:14.720 --> 01:18.970 have different VLANs, for example, VLANs 10 through 20 in the environment on 26 01:18.970 --> 01:20.480 the left and maybe VLANs 27 01:20.480 --> 01:24.770 15 through 25 on the right. And so we're not in perfect alignment with each 28 01:24.770 --> 01:26.000 other, but that's fine 29 01:26.000 --> 01:30.990 be if it's intentional. Now in most organizations, especially enterprise and WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 29 01:26.000 --> 01:30.990 be if it's intentional. Now in most organizations, especially enterprise and 30 01:30.990 --> 01:32.080 campus networks, 31 01:32.080 --> 01:35.840 we're not going to use this because we want to make sure that the entire 32 01:35.840 --> 01:37.040 environment is one 33 01:37.040 --> 01:41.080 seamless domain. But we could probably think of some scenarios, again, like 34 01:41.080 --> 01:41.840 business mergers, 35 01:41.840 --> 01:45.760 where maybe this wouldn't be the case. So this is a way we can differentiate 36 01:45.760 --> 01:47.360 between MST domains 37 01:47.360 --> 01:51.390 or maybe regions at this point is by giving each a separate region name. And 38 01:51.390 --> 01:52.160 then we also have the 39 01:52.160 --> 01:58.400 concept of the revision number. The revision number is a curious addition. 40 01:58.400 --> 02:00.560 Because it's called a WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 40 01:58.400 --> 02:00.560 Because it's called a 41 02:00.560 --> 02:05.950 revision number, it gives the sense that, hey, I'm going to maybe take this 42 02:05.950 --> 02:07.040 switch right here, 43 02:07.040 --> 02:10.900 and I'm going to update the configuration. And therefore, I'm going to take it 44 02:10.900 --> 02:12.000 from revision one 45 02:12.000 --> 02:16.240 to revision two. But given that this needs to match among all of the devices in 46 02:16.240 --> 02:17.040 our domain, 47 02:17.040 --> 02:20.750 I'm going to also have to do this for all of the switches, which is fine. If I 48 02:20.750 --> 02:21.440 'm changing the 49 02:21.440 --> 02:25.290 configuration on one, I probably want to change the configuration on all the 50 02:25.290 --> 02:26.560 rest. Now in production, 51 02:26.560 --> 02:31.510 do we go to the trouble of changing the configuration and revving the revision WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 51 02:26.560 --> 02:31.510 do we go to the trouble of changing the configuration and revving the revision 52 02:31.510 --> 02:34.160 number? Maybe, maybe not, 53 02:34.160 --> 02:37.140 for the most part, this is just something that's going to need to match 54 02:37.140 --> 02:38.800 everywhere. In my experience, 55 02:38.800 --> 02:42.360 we typically set a revision number of one or something like that. And then we 56 02:42.360 --> 02:43.360 just leave it. 57 02:43.360 --> 02:47.120 And we're never going to change it. But it is something that we can include. We 58 02:47.120 --> 02:47.600 just have to be 59 02:47.600 --> 02:52.420 careful with it so that we don't accidentally fragment our domain by making one 60 02:52.420 --> 02:53.200 side have a 61 02:53.200 --> 02:57.840 revision idea of one and one have a two or something along those lines. Now the 62 02:57.840 --> 02:58.880 third one, 63 02:58.880 --> 03:03.440 this is the important one. I mean, all of them are important, of course. But WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 63 02:58.880 --> 03:03.440 this is the important one. I mean, all of them are important, of course. But 64 03:03.440 --> 03:05.920 this is the part, 65 03:05.920 --> 03:10.980 this is the reason why we basically have these different domains is we need a V 66 03:10.980 --> 03:12.320 LAN to instance 67 03:12.320 --> 03:18.880 mapping that matches from one switch to the other. This is what we didn't have 68 03:18.880 --> 03:19.760 to worry about with 69 03:19.760 --> 03:23.780 Cisco. If I had a VLAN 10 on my side and you have a VLAN 10 on your side, we 70 03:23.780 --> 03:24.640 know we both have 71 03:24.640 --> 03:30.030 an instance for VLAN 10. Well, now we're talking about taking two different WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 71 03:24.640 --> 03:30.030 an instance for VLAN 10. Well, now we're talking about taking two different 72 03:30.030 --> 03:31.440 instances and saying, 73 03:31.440 --> 03:37.360 hey, I've got VLANs 10 and 20 on one side and 30 and 40 in this other instance. 74 03:37.360 --> 03:37.840 Maybe these 75 03:37.840 --> 03:42.610 are instances zero and one. And so that's well and good except if you say, well 76 03:42.610 --> 03:43.760 , I've got VLANs 10, 77 03:43.760 --> 03:49.610 20 and 30 in instance zero and I've got instant or VLAN 40 going into instance 78 03:49.610 --> 03:50.720 two. Well, that's a 79 03:50.720 --> 03:55.860 very different topology or set of topologies. We can't do that. We can't 80 03:55.860 --> 03:57.200 interface with one 81 03:57.200 --> 04:01.070 another. And so it's going to fragment our domain. And so at this point, we're WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 81 03:57.200 --> 04:01.070 another. And so it's going to fragment our domain. And so at this point, we're 82 04:01.070 --> 04:02.560 going to require, 83 04:02.560 --> 04:09.440 again, all of these must match. They absolutely have to match or they're not 84 04:09.440 --> 04:10.240 going to be considered 85 04:10.240 --> 04:16.880 to be part of the same MST region or MST domain. So we might ask the question, 86 04:16.880 --> 04:17.520 well, what does it 87 04:17.520 --> 04:21.300 mean if we fragment our domain? I mean, what if we have a bunch of switches 88 04:21.300 --> 04:22.160 here and a bunch of 89 04:22.160 --> 04:27.390 switches over here? And they have different properties. At this point, we would 90 04:27.390 --> 04:28.480 create two 91 04:28.480 --> 04:33.760 different MST regions. And maybe we've got connection among them this way. Well WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 91 04:28.480 --> 04:33.760 different MST regions. And maybe we've got connection among them this way. Well 92 04:33.760 --> 04:34.640 , what that means is 93 04:34.640 --> 04:39.130 within each domain, we're going to have to make sure that it's loop free. So we 94 04:39.130 --> 04:40.400 're going to form 95 04:40.400 --> 04:45.230 our blocked ports internally. But then when we have connections between the two 96 04:45.230 --> 04:46.320 , we're going to treat 97 04:46.320 --> 04:50.750 each one of these almost like it's a giant switch, and make sure that we're 98 04:50.750 --> 04:51.920 blocking one of these 99 04:51.920 --> 05:00.080 links for all VLANs and all instances. So internally, we have to block within a WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 99 04:51.920 --> 05:00.080 links for all VLANs and all instances. So internally, we have to block within a 100 05:00.080 --> 05:01.680 region externally, 101 05:01.680 --> 05:08.030 we're blocking on everything on instance zero is technically how that's going 102 05:08.030 --> 05:09.280 to be perceived. 103 05:09.280 --> 05:13.140 But again, when we zoom out and look at it, we treat this whole region as a 104 05:13.140 --> 05:14.400 switch, we treat this 105 05:14.400 --> 05:18.060 whole region as a switch, I'll put air quotes around the switch icon, if that 106 05:18.060 --> 05:18.720 makes sense, 107 05:18.720 --> 05:21.950 to say it's not really a switch. But we know if we've got two switches 108 05:21.950 --> 05:23.360 connected like this, 109 05:23.360 --> 05:28.160 then we're going to need to decide which one to block. So we need loop free 110 05:28.160 --> 05:29.280 between the regions 111 05:29.280 --> 05:34.520 as well. So long story short, what we see here is that we are going to need WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 111 05:29.280 --> 05:34.520 as well. So long story short, what we see here is that we are going to need 112 05:34.520 --> 05:36.080 individual configurations, 113 05:36.080 --> 05:41.300 individual blocked links, and then a coordinated blocks link between the two as 114 05:41.300 --> 05:42.720 long as there is a 115 05:42.720 --> 05:46.930 loop between the two regions. So it makes things a little bit more complex, 116 05:46.930 --> 05:48.800 naturally again, in a 117 05:48.800 --> 05:54.240 real world production network, we would ideally avoid this, but it does require 118 05:54.240 --> 05:55.680 us matching on all 119 05:55.680 --> 06:00.670 of these configuration parameters. And so that's exactly what we want to do. So WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 119 05:55.680 --> 06:00.670 of these configuration parameters. And so that's exactly what we want to do. So 120 06:00.670 --> 06:01.600 how exactly do we 121 06:01.600 --> 06:05.310 negotiate this? We mentioned that the switches are going to be communicating 122 06:05.310 --> 06:06.400 with these, and it's 123 06:06.400 --> 06:13.070 going to be included within the BPDUs. So it's going to carry the attributes 124 06:13.070 --> 06:14.960 inside of the BPDUs. 125 06:14.960 --> 06:21.440 And we might say, well, wait a second, how are we carrying all of the VLANs and 126 06:21.440 --> 06:22.560 all of the instances? 127 06:22.560 --> 06:26.320 Well, we're technically not, we're going to carry the name and the number, 128 06:26.320 --> 06:27.280 because those are fields 129 06:27.280 --> 06:32.020 we can populate. But for the VLAN to instance mapping, we're going to carry a WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 129 06:27.280 --> 06:32.020 we can populate. But for the VLAN to instance mapping, we're going to carry a 130 06:32.020 --> 06:34.000 hash for the mapping. 131 06:35.040 --> 06:39.440 So we're going to make sure essentially not so much that, hey, here's my exact 132 06:39.440 --> 06:40.640 configuration. 133 06:40.640 --> 06:44.660 But if I include a hash for that configuration, we can compare the hashes and 134 06:44.660 --> 06:46.000 make sure that we at 135 06:46.000 --> 06:49.770 least match configurations. If there is a difference in the configuration, we 136 06:49.770 --> 06:50.720 're not going to know 137 06:50.720 --> 06:54.000 what the difference is, we're just going to know that the hashes don't align, 138 06:54.000 --> 06:54.720 and therefore there 139 06:54.720 --> 07:02.630 must be a difference. And so if my two switches, if we agree on these WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 139 06:54.720 --> 07:02.630 must be a difference. And so if my two switches, if we agree on these 140 07:02.630 --> 07:04.960 parameters, then 141 07:04.960 --> 07:10.000 we're good, and everything will carry on like a rapid per VLAN spanning tree 142 07:10.000 --> 07:10.560 environment where 143 07:10.560 --> 07:17.060 we're just looking for which links to block in the network. But if we disagree, 144 07:17.060 --> 07:19.360 especially if we 145 07:19.360 --> 07:22.560 don't agree on the mapping, because that's something that's pretty easy to 146 07:22.560 --> 07:24.800 create a mistake around, 147 07:24.800 --> 07:28.800 well, at that point, these two switches are going to decide that this is a 148 07:28.800 --> 07:30.080 boundary connection WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 148 07:28.800 --> 07:30.080 boundary connection 149 07:32.320 --> 07:37.840 and that the other switch is part of a different MST region. So we don't need 150 07:37.840 --> 07:38.560 to worry too much 151 07:38.560 --> 07:41.580 about this again, because for the most part, we're going to try to just match 152 07:41.580 --> 07:42.720 all of these together, 153 07:42.720 --> 07:46.440 but just be aware that these attributes are carried inside the BP to use and 154 07:46.440 --> 07:47.200 switches will 155 07:47.200 --> 07:52.560 be able to tell if there's a problem. And those will show up as boundary links 156 07:52.560 --> 07:53.360 in our show spanning 157 07:53.360 --> 07:57.890 tree outputs. So this keyword will show up in our configurations. If we ever 158 07:57.890 --> 07:58.640 see that, 159 07:58.640 --> 08:02.690 now we know what it's saying. It's saying that we need to check these WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 159 07:58.640 --> 08:02.690 now we know what it's saying. It's saying that we need to check these 160 08:02.690 --> 08:03.680 parameters and make sure 161 08:03.680 --> 08:05.440 that the configurations match.