WEBVTT 00:00:00.000 --> 00:00:06.920 Alright, now it's time to dive into our final spanning tree protocol discussion, and that 00:00:06.920 --> 00:00:16.320 is on multiple spanning tree protocol, MSTP, also known as, what did we say earlier, 802.1S, 00:00:16.320 --> 00:00:25.840 or multiple spanning tree, you might see MST, MSTP, 802.1S, if you see any of those, referring 00:00:25.840 --> 00:00:27.879 to the exact same thing on the certification exam. 00:00:27.879 --> 00:00:40.279 Alright, so there's many different reasons why we want to use multiple spanning tree protocol, so one of the reasons that we talked about earlier was the fact that this is the only version of spanning tree protocol that works the same way on non-Cisco equipment and Cisco equipment. 00:00:40.279 --> 00:00:52.840 So on a certification exam, if they ever have a scenario that mentions Cisco and non-Cisco equipment in the exact same scenario, and you're dealing with layer two, and you are dealing with spanning tree protocol, immediately think multiple spanning tree protocol. 00:00:52.840 --> 00:01:00.680 That's right where I want you to go with that, because that is the best solution possible, and that's what they're going to be testing you on in that type of situation. 00:01:00.680 --> 00:01:05.639 So right away, multi-vendor support, multiple spanning tree protocol is the way to go. 00:01:05.639 --> 00:01:12.879 Alright, however, what is the other reason why we want to use multiple spanning tree protocol in pretty much most of our modern day environments? 00:01:12.879 --> 00:01:18.080 It is because there are some limitations in regards to spanning tree protocol. 00:01:18.080 --> 00:01:27.519 Does anybody know how many trees we can have when we're using Pervyland Spanning Tree Plus or Rapid Pervyland Spanning Tree Plus? 00:01:27.519 --> 00:01:29.800 Does anybody know how many trees? 00:01:29.800 --> 00:01:30.879 What do I say by trees? 00:01:30.879 --> 00:01:38.199 I mean, how many different spanning trees can we have running on a single device? 00:01:41.480 --> 00:01:46.959 Okay, well, it typically depends on the platform, so nobody's going to have the perfect answer here. 00:01:46.959 --> 00:01:50.120 But usually, it's around 256 or less. 00:01:52.919 --> 00:02:03.360 So that means in this part of my network here, I cannot have more than 256 trees. 00:02:04.239 --> 00:02:09.520 Therefore, how many VLANs can I have then in that part of the network? 00:02:09.520 --> 00:02:16.839 256. 00:02:16.839 --> 00:02:25.240 Because what happens if I create 260 VLANs? 00:02:25.240 --> 00:02:37.080 Well, if I create 260 VLANs, 256 will have a spanning tree instance running. 00:02:37.080 --> 00:02:45.399 But the other four will not. 00:02:45.399 --> 00:02:54.479 They will be those four extra VLANs 100% looping all the time. 00:02:54.479 --> 00:03:02.720 Oh, what if you had 300 VLANs? 00:03:02.720 --> 00:03:04.440 Well, now it's getting worse, right? 00:03:04.440 --> 00:03:06.720 You could only have 256. 00:03:06.720 --> 00:03:08.559 So typically, it's 256. 00:03:08.559 --> 00:03:13.559 I have seen a few platforms that only support 128 VLANs, okay? 00:03:13.559 --> 00:03:15.600 So the number you're not going to be testing on, that's the key. 00:03:15.600 --> 00:03:19.639 You're not going to be testing on the actual number of trees you could have on the exam. 00:03:19.639 --> 00:03:27.960 But I want you to realize that if you have an excessive number of VLANs, 500, 600, 700, 00:03:27.960 --> 00:03:34.080 on the certification exam or in the real world, these really are not your go-to options at all. 00:03:34.080 --> 00:03:35.960 And they are the defaults, right? 00:03:36.000 --> 00:03:38.720 You really need to go with multiple spanning tree protocol. 00:03:38.720 --> 00:03:43.240 Because multiple spanning tree protocol is going to allow us to circumvent this limitation. 00:03:43.240 --> 00:03:49.919 So consider right now the fact that we have, let's say I'm going to use 1,000 VLANs, okay? 00:03:49.919 --> 00:03:55.679 Now, we know based on what I just said that with 802.1W, right, we would have one tree. 00:03:55.679 --> 00:04:00.440 That's it, just one tree for all 1,000 VLANs based on what we talked about earlier today, okay? 00:04:00.440 --> 00:04:04.440 But rapid per VLAN spanning tree plus, we'd have one tree per VLAN, therefore 1,000 trees, 00:04:04.440 --> 00:04:08.199 which is not even possible, as we just said, because it would max out at 256. 00:04:08.199 --> 00:04:11.960 But just to keep the story going, right, think about that for a second. 00:04:11.960 --> 00:04:18.320 One tree with 802.1W, all the VLANs follow that tree, that diagram, okay? 00:04:18.320 --> 00:04:21.239 Rapid per VLAN spanning 1,000 trees, okay? 00:04:21.239 --> 00:04:25.320 But with multiple spanning tree protocol, I pick the number of trees. 00:04:25.320 --> 00:04:29.559 I pick the number of trees. 00:04:29.559 --> 00:04:41.559 So if I have 1,000 VLANs, I could turn around and I could have two trees and put certain VLANs in each tree. 00:04:41.559 --> 00:04:47.799 I control the number of trees in which VLANs are in the trees. 00:04:47.799 --> 00:04:51.559 Now, let's just look at this diagram for a second. 00:04:51.559 --> 00:04:59.799 Based on our conversation earlier today in our spanning tree protocol discussion, 00:04:59.799 --> 00:05:04.359 we said typically we're going to place our root bridges where, folks? 00:05:04.359 --> 00:05:15.559 Where are we going to do that? 00:05:15.559 --> 00:05:17.480 As close as possible to the layer three. 00:05:17.480 --> 00:05:19.959 So in our case here, our what? 00:05:19.959 --> 00:05:26.679 Our distribution layer switches. 00:05:30.279 --> 00:05:31.320 That's where we're going to put it. 00:05:33.160 --> 00:05:34.359 So let me ask you this. 00:05:36.839 --> 00:05:44.600 How many devices in total do I have, in this case, to be root bridges? 00:05:48.279 --> 00:05:56.279 This too. 00:05:57.160 --> 00:06:02.440 I got one here and I got one here because we're not going to use these two, right? 00:06:04.440 --> 00:06:05.160 All right. 00:06:05.160 --> 00:06:13.880 So if I could have this as a root bridge for a tree and this as a root bridge for a tree, 00:06:14.679 --> 00:06:21.399 how many trees, how many unique trees can we have? 00:06:22.519 --> 00:06:26.119 So if I could have a root bridge here for a tree and a root bridge here for a tree, 00:06:26.119 --> 00:06:29.959 how many unique trees can we have in this topology? 00:06:34.200 --> 00:06:35.640 It's two, right? 00:06:35.640 --> 00:06:38.760 One tree for each root bridge. 00:06:38.760 --> 00:06:40.839 One tree for each distribution layer switch. 00:06:40.839 --> 00:06:49.720 So really, two trees, two unique trees, one anchored here, one anchored here. 00:06:54.440 --> 00:07:01.239 Just think about earlier when we did VLAN 10 and VLAN 50. 00:07:01.239 --> 00:07:03.079 Do you remember what it looked like? 00:07:03.640 --> 00:07:04.839 Well, let me remind you. 00:07:06.440 --> 00:07:07.880 So one of them was here. 00:07:09.480 --> 00:07:10.519 One of them was here. 00:07:11.720 --> 00:07:14.760 VLAN 10, VLAN 50. 00:07:16.040 --> 00:07:17.799 Okay, but what about VLAN 20? 00:07:19.079 --> 00:07:20.760 Where's VLAN 20's root bridge? 00:07:20.760 --> 00:07:22.040 Well, by default, it's here. 00:07:22.839 --> 00:07:26.440 So VLAN 20 has a tree anchored to DSW1. 00:07:26.440 --> 00:07:29.239 Okay, what about VLAN 200 by default? 00:07:29.239 --> 00:07:31.239 Well, it's also anchored here by default. 00:07:34.679 --> 00:07:37.559 So I have four trees right now in this environment, 00:07:38.519 --> 00:07:42.040 but there's really only two unique trees we can have, right? 00:07:43.160 --> 00:07:46.279 One that is anchored here and one that is anchored there. 00:07:46.279 --> 00:07:50.760 So meaning right now, I've got three trees that are all anchored here. 00:07:51.959 --> 00:07:55.720 Well, with multiple spanning tree protocol, if that's what I want, 00:07:55.720 --> 00:07:59.000 I could have one tree with all three VLANs in it. 00:07:59.880 --> 00:08:02.440 That's what I can do while having this one here. 00:08:02.760 --> 00:08:07.079 That's the difference between running PVST plus or rapid PVST plus 00:08:07.079 --> 00:08:09.239 versus something like multiple spanning tree protocol. 00:08:09.799 --> 00:08:15.959 I now have the ability to ensure that I'm running the minimum number of trees 00:08:15.959 --> 00:08:17.239 based on my architecture. 00:08:17.880 --> 00:08:21.959 So instead of having 1,000 trees, again, we know it's not possible. 00:08:21.959 --> 00:08:24.519 You can only like basically 256 max, okay? 00:08:24.519 --> 00:08:30.679 But 1,000 trees that are going to be all anchored here or anchored here. 00:08:31.640 --> 00:08:35.000 Why not just have two trees 00:08:38.119 --> 00:08:43.640 and put all the VLANs in this tree and put the other VLANs in this tree, right? 00:08:43.640 --> 00:08:44.760 Half here, half there. 00:08:44.760 --> 00:08:46.840 We can do that with multiple spanning tree protocol. 00:08:49.640 --> 00:08:53.719 So now my router only has to send what? 00:08:53.719 --> 00:08:55.640 Enough BPDUs for what? 00:08:55.640 --> 00:08:59.799 Those two trees instead of 1,000 trees, right? 00:08:59.799 --> 00:09:02.039 Performance is increased here as well. 00:09:03.159 --> 00:09:07.320 So a lot of us are running rapid PVST plus in our environment. 00:09:07.320 --> 00:09:10.200 And we have like 20 VLANs down here when in reality, 00:09:11.000 --> 00:09:13.400 we really could use multiple spanning tree protocol 00:09:14.119 --> 00:09:17.320 and group VLANs together on a common root bridge. 00:09:17.320 --> 00:09:19.400 Group VLANs together on a common root bridge. 00:09:20.200 --> 00:09:21.719 Half the traffic may be going through here. 00:09:21.719 --> 00:09:23.320 Half the traffic may be going through here. 00:09:26.200 --> 00:09:28.280 Things to consider, right? 00:09:28.280 --> 00:09:29.719 Reduce the total number of trees. 00:09:29.719 --> 00:09:31.719 Build trees, place the VLANs in the trees you want. 00:09:32.359 --> 00:09:35.479 So now when it comes to our bridge protocol data unit, 00:09:36.520 --> 00:09:39.080 our BPDU and our what? 00:09:39.080 --> 00:09:43.000 Our bridge ID or bridge ID has changed now. 00:09:44.440 --> 00:09:48.679 Because our bridge ID, instead of it being the VLAN, 00:09:48.679 --> 00:09:52.200 notice it says instance now instead of VLAN. 00:09:53.080 --> 00:09:54.919 What do we mean by instance? 00:09:54.919 --> 00:09:57.640 Well, the instance refers to the tree. 00:09:58.679 --> 00:10:01.479 So if I have a tree that's anchored here, 00:10:01.479 --> 00:10:02.599 and this is the root bridge, 00:10:03.559 --> 00:10:08.200 this might be, for example, instance number one. 00:10:09.080 --> 00:10:12.919 So the bridge priority for instance number one can be controlled. 00:10:14.119 --> 00:10:16.119 So instance number one would be like one. 00:10:16.119 --> 00:10:19.159 So instead of doing it on a VLAN by VLAN basis, 00:10:19.159 --> 00:10:22.599 we're doing it on an instance by instance basis. 00:10:22.599 --> 00:10:26.200 Think that an instance equals a tree. 00:10:27.159 --> 00:10:32.119 And your tree is going to have whatever VLANs you want inside of it now. 00:10:33.239 --> 00:10:35.239 So likewise, this could be the root bridge. 00:10:36.679 --> 00:10:42.840 The root bridge for instance number two, right? 00:10:42.840 --> 00:10:47.479 So any BPDUs for that one are going to have the bridge priority of a two in it there. 00:10:47.479 --> 00:10:52.280 So the bridge priority number itself, zero through 65,535, 00:10:52.280 --> 00:10:53.320 just like we saw before. 00:10:53.320 --> 00:10:57.239 But now we have instance one, two, three, four, and so on and so forth. 00:10:57.239 --> 00:10:58.919 And you can only build up to a maximum of, 00:11:00.440 --> 00:11:03.159 last time I checked was 16 trees, I believe. 00:11:03.159 --> 00:11:03.799 And that's okay. 00:11:05.080 --> 00:11:07.320 In this case, look, we only need two, right? 00:11:07.320 --> 00:11:10.359 But you could do up to 16 trees with multiple spanning tree protocol. 00:11:11.479 --> 00:11:12.919 That's not something you'll be tested on. 00:11:12.919 --> 00:11:14.280 So you don't have to worry about that. 00:11:14.280 --> 00:11:14.679 All right. 00:11:14.679 --> 00:11:21.719 Now, in order for you to be part of the same spanning tree protocol environment, 00:11:23.799 --> 00:11:31.880 you have to be part of what is called the same MSTP region with the same information. 00:11:32.760 --> 00:11:37.400 So all of these switches that are going to be participating in multiple spanning tree protocol, 00:11:38.039 --> 00:11:43.239 they are going to have to be configured the exact same way with the exact same parameters. 00:11:43.880 --> 00:11:47.479 So an MSTP region is a collection of switches sharing the same 00:11:47.479 --> 00:11:50.280 view of the spanning tree protocol topology. 00:11:50.679 --> 00:11:54.919 So they are going to partition it the same way in the logical way that it needs to be partitioned. 00:11:54.919 --> 00:11:58.119 They are going to be able to agree on the same root bridges and all that stuff. 00:11:58.119 --> 00:12:04.919 So if any of these values I'm about to show you are ever different on any of the switches, 00:12:04.919 --> 00:12:06.359 then you are not part of the same region. 00:12:06.359 --> 00:12:10.200 Therefore, you'll build your own tree totally separate of everyone else. 00:12:10.200 --> 00:12:17.479 So it's really important that these three parameters are perfect in your configuration 00:12:18.440 --> 00:12:23.000 on all of the switches that are part of the same spanning tree region. 00:12:23.799 --> 00:12:26.679 So we know that this one, this one, this one, and this one, 00:12:26.679 --> 00:12:30.840 they all need to be in the same region because we want them to build a tree together. 00:12:31.479 --> 00:12:37.640 So therefore, the configuration name, the region name has to be the exact same on all four devices. 00:12:38.359 --> 00:12:41.159 The revision number has to be the same on all four devices. 00:12:41.159 --> 00:12:44.760 Now, the revision number here is totally different than VTP. 00:12:44.919 --> 00:12:48.039 So in VTP, remember, every time you made a change to the configuration, 00:12:48.039 --> 00:12:49.640 the revision number went up by one. 00:12:50.440 --> 00:12:52.919 And that was used to help with synchronization. 00:12:52.919 --> 00:12:58.039 The configuration revision number here is for you when it comes to change management. 00:12:58.039 --> 00:12:58.840 That's what it is. 00:12:59.640 --> 00:13:00.679 Change management. 00:13:00.679 --> 00:13:03.640 And for you, for your configuration management as well. 00:13:03.640 --> 00:13:06.520 So that way there, you can keep track of your changes 00:13:06.520 --> 00:13:09.799 and you can keep track of your configuration revisions that you have done. 00:13:09.799 --> 00:13:12.119 It's just a manual number. 00:13:12.119 --> 00:13:16.440 So if you make a change, you're supposed to update the number on all of your devices. 00:13:16.440 --> 00:13:18.359 And therefore, you keep it consistent. 00:13:18.359 --> 00:13:20.039 So once you make a change, you update the number. 00:13:20.039 --> 00:13:21.799 But the number has to be the same on all the devices. 00:13:21.799 --> 00:13:24.520 So if any number is not updated, then what? 00:13:24.520 --> 00:13:26.039 It's going to build a different tree. 00:13:26.039 --> 00:13:27.799 It's not going to be part of the group. 00:13:27.799 --> 00:13:30.679 And then lastly, the instance, the VLAN mappings, that is what? 00:13:30.679 --> 00:13:32.679 The building of the trees. 00:13:32.679 --> 00:13:35.479 So you are going to specify, I want this many trees. 00:13:35.479 --> 00:13:37.799 And these are the VLANs I want in every single tree. 00:13:37.799 --> 00:13:40.039 So let me just show you a configuration of that right here. 00:13:42.919 --> 00:13:45.080 So you'll see DSW1. 00:13:45.080 --> 00:13:48.200 I'm typing in spanning tree MST configuration. 00:13:48.200 --> 00:13:50.520 And then I'm in MST configuration mode. 00:13:51.400 --> 00:13:53.239 And from there, I put the revision number of four. 00:13:53.239 --> 00:13:55.880 So I'm just adding a number I picked, okay? 00:13:55.880 --> 00:13:57.960 So in this case, I'm starting with four. 00:13:57.960 --> 00:14:00.440 You probably start with one and work your way up from there. 00:14:00.440 --> 00:14:02.679 Every time you make a change, you update your revision number. 00:14:02.679 --> 00:14:04.520 And you would have to do that on every single device. 00:14:04.520 --> 00:14:06.440 So it's a manual revision number. 00:14:06.440 --> 00:14:07.320 And it has to be the same. 00:14:07.320 --> 00:14:10.440 So you can see, same, same, same, same, right? 00:14:10.440 --> 00:14:12.280 Configuration name. 00:14:12.840 --> 00:14:14.119 I named it Encore. 00:14:14.119 --> 00:14:15.080 I named it Encore. 00:14:15.080 --> 00:14:16.039 I named it Encore. 00:14:16.039 --> 00:14:16.760 I named it Encore. 00:14:16.760 --> 00:14:17.640 So same. 00:14:17.640 --> 00:14:19.320 And then the instance to VLAN mapping. 00:14:19.320 --> 00:14:21.080 So this is going to be tree number one. 00:14:21.960 --> 00:14:24.359 And these are the VLANs I want in tree number one. 00:14:24.359 --> 00:14:26.119 This is instance number two, tree number two. 00:14:26.119 --> 00:14:28.359 So I'm just using thousand VLANs as an example here. 00:14:29.159 --> 00:14:31.799 But in our environment, and you'll see I've done the same thing. 00:14:31.799 --> 00:14:33.880 So look, the config has to be 100% the same. 00:14:33.880 --> 00:14:35.640 There is no exception to this rule. 00:14:35.640 --> 00:14:38.760 If one of these values are out of place, then it's not going to work. 00:14:41.080 --> 00:14:42.039 You're going to have discrepancy. 00:14:42.039 --> 00:14:46.679 So in this case, for example, we go to ASW1, type in configure terminal MST configuration. 00:14:53.799 --> 00:14:56.520 And what I want to point out to you is that you can do the configuration 00:14:56.520 --> 00:14:58.520 without affecting your current spanning tree topology. 00:14:58.520 --> 00:14:59.960 That's all this is, a configuration. 00:15:00.840 --> 00:15:02.359 A configuration that you then apply. 00:15:02.919 --> 00:15:04.919 So I'm running RapidSpanningTree protocol right now. 00:15:04.919 --> 00:15:06.039 I can do all this configuration. 00:15:06.039 --> 00:15:08.280 It doesn't affect my RapidSpanningTree protocol right now. 00:15:09.159 --> 00:15:12.520 So, for example, let's go ahead and type in revision. 00:15:14.119 --> 00:15:16.200 Put a revision number of six here for fun. 00:15:16.200 --> 00:15:18.599 Let's give it a name, ENCOR. 00:15:18.599 --> 00:15:23.159 And then let's go ahead and say, like, for example, instance, instance number one. 00:15:23.640 --> 00:15:29.479 Let's pretend that we're going to put VLANs 10 and 200 in this one. 00:15:29.479 --> 00:15:35.719 And then instance number two, we're going to do VLANs, what is it, 20 and 50. 00:15:36.520 --> 00:15:37.239 That's what we're going to do. 00:15:38.760 --> 00:15:39.000 All right. 00:15:39.000 --> 00:15:40.440 So there's my configuration. 00:15:40.440 --> 00:15:45.239 So do show run pipe to section MST. 00:15:49.239 --> 00:15:50.280 SpanningTree protocol. 00:15:52.760 --> 00:15:53.479 All right. 00:15:53.479 --> 00:15:53.880 Nope. 00:15:53.880 --> 00:15:54.679 Not that one either. 00:15:55.479 --> 00:15:56.679 Show run. 00:16:05.080 --> 00:16:05.640 Show run. 00:16:06.440 --> 00:16:09.080 I forget what it is. 00:16:11.960 --> 00:16:12.280 All right. 00:16:12.280 --> 00:16:12.840 So there you go. 00:16:15.239 --> 00:16:16.440 So let's go ahead now. 00:16:16.440 --> 00:16:19.400 You can just copy and paste this configuration to all the other devices, 00:16:19.400 --> 00:16:24.039 because they've got to be the exact same. 00:16:34.520 --> 00:16:35.080 There you go. 00:16:35.719 --> 00:16:36.280 OK. 00:16:36.280 --> 00:16:39.799 So now that they all have them the same, if we take a look now, 00:16:39.799 --> 00:16:43.799 we type in something like show SpanningTree MST configuration, 00:16:44.679 --> 00:16:47.400 you'll see that it says right now we're not in MST mode. 00:16:47.400 --> 00:16:49.239 So the configuration is ready to go. 00:16:49.239 --> 00:16:51.880 We just haven't enabled it yet on all of our devices. 00:16:53.159 --> 00:16:57.640 And you'll see now that every VLAN by default is part of instance zero. 00:16:57.640 --> 00:16:59.320 So there's this instance zero. 00:16:59.320 --> 00:17:02.679 So you actually have, even though we created two trees, we actually have three trees. 00:17:03.239 --> 00:17:08.280 And instance zero is going to be the tree for all the other VLANs if they exist on your device. 00:17:09.079 --> 00:17:16.439 And then if you have VLANs 10 through 19, no, that's not what I wanted. 00:17:17.079 --> 00:17:19.239 How did I end up with that config? 00:17:23.160 --> 00:17:24.920 It's not what we wanted, was it? 00:17:24.920 --> 00:17:25.160 No. 00:17:26.359 --> 00:17:26.520 No. 00:17:26.520 --> 00:17:28.199 What did I type in to cause that? 00:17:28.199 --> 00:17:29.800 Did I accidentally hit a dash? 00:17:30.359 --> 00:17:32.839 Oh, yes, I put a dash. 00:17:33.800 --> 00:17:35.160 That's not what we wanted. 00:17:35.160 --> 00:17:36.839 Let's fix that because that's not good. 00:17:36.839 --> 00:17:37.640 That's not what we want. 00:17:38.520 --> 00:17:39.880 So we definitely want to fix that. 00:17:47.719 --> 00:17:49.079 Okay, so configure terminal. 00:17:50.839 --> 00:17:53.719 So VLAN 10 comma 200. 00:17:54.040 --> 00:17:54.680 200. 00:17:56.199 --> 00:18:02.359 And then we want instance number two, VLAN 20 comma 50. 00:18:03.479 --> 00:18:04.199 I did it again. 00:18:06.280 --> 00:18:06.760 All right. 00:18:06.760 --> 00:18:08.439 Now let's take a look at our running config. 00:18:18.680 --> 00:18:22.439 So I'm going to have to probably delete it. 00:18:23.000 --> 00:18:29.079 All right. 00:18:36.040 --> 00:18:36.599 All right. 00:18:36.599 --> 00:18:40.119 And then we'll put in this command here now. 00:18:42.599 --> 00:18:44.839 We'll put in these two values here. 00:18:44.839 --> 00:18:59.479 We'll type in instance one, VLAN 10 comma. 00:19:11.479 --> 00:19:13.560 Doesn't take effect until I log out. 00:19:13.560 --> 00:19:14.119 That's correct. 00:19:15.079 --> 00:19:17.479 So you got to exit the mode before it actually takes effect. 00:19:18.199 --> 00:19:20.680 So let's just do our second instance and make sure we got it. 00:19:20.680 --> 00:19:27.479 So we said 20 and 50. 00:19:38.680 --> 00:19:41.479 That looks a lot better. 00:19:42.359 --> 00:19:43.560 Okay. 00:19:43.560 --> 00:19:45.479 So we'll copy and paste that over here. 00:19:45.479 --> 00:19:47.160 But first we're going to have to say new. 00:19:51.160 --> 00:20:02.119 And then paste this one in. 00:20:08.599 --> 00:20:09.000 There you go. 00:20:09.000 --> 00:20:09.719 Now we should be good. 00:20:11.479 --> 00:20:18.520 All right. 00:20:28.520 --> 00:20:32.520 Oh, my gosh. 00:20:34.839 --> 00:20:35.719 There we go. 00:20:35.719 --> 00:20:36.680 That looks a lot better. 00:20:37.719 --> 00:20:38.040 All right. 00:20:38.040 --> 00:20:42.920 So with that in mind, as you can see, this is going to match on all of our devices. 00:20:42.920 --> 00:20:45.239 And if it doesn't match on all of our devices, then it's not going to work. 00:20:45.239 --> 00:20:47.719 So something to pay attention to on the exam is if you're ever comparing 00:20:48.359 --> 00:20:52.839 this configuration to the configuration on another device, another device, another device 00:20:52.839 --> 00:20:56.920 to figure out why something's not working, just come flat out and look for these things. 00:20:56.920 --> 00:20:58.680 Is that the same on all the devices? 00:20:58.680 --> 00:21:00.680 Is that the same on all the devices? 00:21:00.680 --> 00:21:03.239 Is this the exact same on all the devices? 00:21:03.239 --> 00:21:06.040 Because if it's not, that is why it's not working. 00:21:06.040 --> 00:21:08.760 And then you're going to have to answer the multiple choice question, the drag and drop, 00:21:08.760 --> 00:21:14.119 or the what simulation and make any corrections that are necessary in order to get it to work. 00:21:14.119 --> 00:21:14.359 OK. 00:21:14.359 --> 00:21:15.640 So I got an exit out here. 00:21:17.319 --> 00:21:19.160 First for it to take effect on that one. 00:21:19.160 --> 00:21:20.439 We'll take a peek now. 00:21:20.439 --> 00:21:20.920 So, yeah. 00:21:20.920 --> 00:21:22.439 So just basically you're comparing. 00:21:22.439 --> 00:21:23.319 Are they the same? 00:21:23.319 --> 00:21:24.199 Are they the same? 00:21:24.199 --> 00:21:24.920 Are they the same? 00:21:24.920 --> 00:21:26.680 And right now they look like they're the same. 00:21:26.680 --> 00:21:26.920 Right. 00:21:27.959 --> 00:21:29.319 So how do you turn it on now? 00:21:29.319 --> 00:21:33.400 You go to every single device and you would type in spanning tree mode MST. 00:21:33.959 --> 00:21:34.520 Enter. 00:21:35.079 --> 00:21:38.520 Go over here, spanning tree mode, MST. 00:21:47.479 --> 00:21:51.560 And now we're running multiple spanning tree protocol on all of the devices. 00:21:55.000 --> 00:21:56.680 So let that cook for just a moment. 00:21:56.680 --> 00:21:57.479 All right. 00:21:57.479 --> 00:22:02.920 Because it can take a little bit of time to fully converge and resolve itself of any kind. 00:22:03.000 --> 00:22:04.760 Of any conflicts that actually exist. 00:22:06.280 --> 00:22:09.400 So we just saw that in our environment when we configured it. 00:22:10.040 --> 00:22:10.439 Right. 00:22:10.439 --> 00:22:15.319 To transition over to multiple spanning tree protocol, as we saw, spanning tree mode MST. 00:22:16.359 --> 00:22:21.880 So now when you're looking at the output, you'll look at things like the actual tree itself. 00:22:21.880 --> 00:22:25.479 So instead of looking at it on a VLAN by VLAN basis, like you did with 00:22:27.319 --> 00:22:30.359 per VLAN spanning tree plus a rapid pre-linked VLAN spanning tree plus, 00:22:30.359 --> 00:22:32.760 you're going to look at it on a tree by tree basis. 00:22:33.319 --> 00:22:36.439 And so you'll see the trees that are mapped in that particular case. 00:22:36.439 --> 00:22:37.800 So let's see if we can see that now. 00:22:37.800 --> 00:22:41.000 Do show spanning tree MST1 as an example. 00:22:41.000 --> 00:22:41.560 There you go. 00:22:42.680 --> 00:22:43.000 Right. 00:22:44.760 --> 00:22:51.640 And if we go over to something like DSW1 and we type in do show span MST1, 00:22:53.160 --> 00:22:56.920 we'll see that we're not the root port for VLAN 10 or like we were before. 00:22:56.920 --> 00:22:57.560 Why is that? 00:22:57.560 --> 00:22:59.479 Because this is totally different. 00:22:59.479 --> 00:23:02.520 So right now we're at the factory default settings when it comes to 00:23:02.520 --> 00:23:05.719 multiple spanning tree protocol, except for the trees we have created here. 00:23:06.280 --> 00:23:09.319 So meaning that everything we did in our previous example, 00:23:09.319 --> 00:23:13.560 where DSW1 was the root bridge and all that stuff does not apply anymore. 00:23:13.560 --> 00:23:15.079 But we can make it happen. 00:23:15.640 --> 00:23:20.520 So in this case, for example, you would type in spanning tree MST1 priority zero. 00:23:20.520 --> 00:23:24.280 And now that would make me the root bridge for this entire tree. 00:23:24.920 --> 00:23:25.079 Right. 00:23:25.079 --> 00:23:26.760 Right now I'm not the root bridge for the entire tree. 00:23:26.760 --> 00:23:26.920 Why? 00:23:26.920 --> 00:23:29.400 Because it doesn't say I'm the root bridge for the entire tree. 00:23:30.359 --> 00:23:32.599 Not all my ports are designated ports. 00:23:32.599 --> 00:23:34.119 So now let's take a look at it. 00:23:34.119 --> 00:23:37.959 Now that we have a priority of zero, you'll see that now I am now the root bridge. 00:23:38.839 --> 00:23:40.599 And you'll see that we have all designated ports. 00:23:40.599 --> 00:23:43.640 This is in a dispute state right now because it's still converging. 00:23:43.640 --> 00:23:46.599 So once that all sorts itself out, then everything's going to be good. 00:23:46.599 --> 00:23:49.640 If we go to ASW1 as an example and take a peek at MST1, 00:23:50.520 --> 00:23:54.920 notice that our port fast configuration carried over. 00:23:54.920 --> 00:23:56.680 So port fast configs will carry over. 00:23:56.680 --> 00:23:58.920 BPDU guard configs will carry over. 00:23:58.920 --> 00:23:59.800 No problem there. 00:24:01.319 --> 00:24:04.599 But you'll see here that what do we have? 00:24:06.439 --> 00:24:11.479 45 is not the root port right now. 00:24:11.479 --> 00:24:12.280 It's 46. 00:24:12.280 --> 00:24:14.920 So my question is, is did our port priorities? 00:24:14.920 --> 00:24:15.160 Yeah. 00:24:15.160 --> 00:24:17.800 So even the port priorities carried over, as you can see. 00:24:17.800 --> 00:24:20.439 So any of those interface adjustments we made, 00:24:20.439 --> 00:24:25.239 so on the interface changing cost or interface changing port IDs, 00:24:25.239 --> 00:24:27.319 all of that stuff got carried over. 00:24:27.319 --> 00:24:28.760 Port fast gets carried over. 00:24:28.760 --> 00:24:30.680 BPDU guard gets carried over. 00:24:30.680 --> 00:24:33.319 But things like your root bridge doesn't get carried over. 00:24:33.319 --> 00:24:36.040 So that might be something you'd have to adjust after that fact. 00:24:37.239 --> 00:24:37.479 All right. 00:24:37.479 --> 00:24:38.439 Now everything's fine. 00:24:38.439 --> 00:24:39.640 Everything's in the forwarding state. 00:24:39.640 --> 00:24:41.560 We don't have any disputes right now. 00:24:41.560 --> 00:24:45.000 And notice that the cost is automatically using the long path cost. 00:24:45.560 --> 00:24:49.319 The long path cost as opposed to the short path cost in a particular case. 00:24:49.319 --> 00:24:51.479 And that automatically adjusts on all our devices. 00:24:53.239 --> 00:24:56.839 So just like before, changing port cost is super simple. 00:24:56.839 --> 00:25:03.880 But instead of changing it on a VLAN by VLAN basis, you have to do it on a what? 00:25:03.880 --> 00:25:11.160 You're going to have to do it on a instance by instance basis in this case. 00:25:11.160 --> 00:25:12.680 So notice it says 4 here. 00:25:12.680 --> 00:25:16.680 I think it's because if we look at show run for interface, 00:25:16.680 --> 00:25:19.800 gigabit ethernet 1 size 0 size 45, we had the cost set to 4. 00:25:19.800 --> 00:25:21.000 Yeah, we did. 00:25:21.000 --> 00:25:26.119 So as you can see, setting the cost of 4 overruled anything that was going on over there. 00:25:26.119 --> 00:25:34.439 So let's go ahead and change our cost or just remove this command on that interface right now. 00:25:43.640 --> 00:25:45.479 And that'll change over here shortly. 00:25:45.479 --> 00:25:46.040 Oh, no, wait. 00:25:46.040 --> 00:25:47.079 I only did the one interface. 00:25:47.079 --> 00:25:48.439 So 46 as well. 00:25:57.079 --> 00:25:58.119 All right. 00:25:58.119 --> 00:26:01.640 So I'm just trying to show you – just walking you through some of the things that we've already done 00:26:02.199 --> 00:26:03.400 earlier today. 00:26:03.400 --> 00:26:07.000 And you'll see everything else that we talked about applies the same to multiple spanning 00:26:07.000 --> 00:26:08.760 tree protocol, which is great. 00:26:08.760 --> 00:26:11.880 There's not a big learning curve to it except for that configuration we did. 00:26:12.599 --> 00:26:15.400 And then adjusting your – everything based on what? 00:26:15.400 --> 00:26:18.920 MST as opposed to VLANs. 00:26:19.959 --> 00:26:22.439 So I have some slides for that, too, if you ever want to review the slides. 00:26:22.439 --> 00:26:25.400 So changing the priority, making DSW1 the root bridge. 00:26:26.199 --> 00:26:30.439 Right now it's the root bridge for the entire MST tree in that case. 00:26:30.439 --> 00:26:37.079 So if we want to do DSW2 as the root bridge now for MST2, we can go ahead and do that. 00:26:37.640 --> 00:26:43.160 And so now, for example, VLANs 1 through 500 are using DSW1 as the root bridge in this scenario, 00:26:43.160 --> 00:26:48.040 and 501 through 1,000 are using MST2 as the root bridge, which is awesome. 00:26:48.040 --> 00:26:52.920 So the thing I want you to realize is that as we're exchanging BPDUs and stuff like that, 00:26:52.920 --> 00:26:55.719 that is going to be extremely different now with multiple spanning tree protocol. 00:26:56.439 --> 00:27:01.800 And the reason why is because we don't have to share information that is already 00:27:01.800 --> 00:27:03.079 pre-configured on ourselves. 00:27:03.079 --> 00:27:09.880 So when you think about something like our revision number, our revision – our configuration name, 00:27:09.880 --> 00:27:16.680 and you think about our instance to VLAN mapping, all of that stuff – all of that stuff is what? 00:27:16.680 --> 00:27:18.599 Configured on every single device. 00:27:19.319 --> 00:27:22.199 So we don't have to share that information with each other. 00:27:22.199 --> 00:27:25.959 But what we do have to do is verify that we have the same information. 00:27:25.959 --> 00:27:30.359 So when you look here at something like DSW1, we have a digest that is created 00:27:31.719 --> 00:27:33.479 for that configuration. 00:27:34.040 --> 00:27:35.640 We have a digest that is created. 00:27:35.640 --> 00:27:37.560 Notice the digest is the exact same. 00:27:38.520 --> 00:27:39.479 Why is that important? 00:27:39.479 --> 00:27:43.319 Because this is how they verify that they're part of the exact same region. 00:27:43.319 --> 00:27:48.280 So whenever we exchange our BPDUs, we don't have to send the instance ID mappings in that. 00:27:48.280 --> 00:27:50.359 We don't have to send our revision number. 00:27:50.359 --> 00:27:52.680 We don't have to send our domain name, like things like that. 00:27:53.160 --> 00:27:53.400 Why? 00:27:53.400 --> 00:27:55.239 Because we just have to send the digest. 00:27:55.800 --> 00:27:58.760 And the digest is a way that we can essentially authenticate with each other and say, 00:27:58.760 --> 00:28:00.520 oh, yeah, we're part of the same region. 00:28:00.520 --> 00:28:04.040 Therefore, we can exchange or I can accept this BPDU from you, 00:28:04.040 --> 00:28:07.640 and I can go ahead and process this BPDU from you because the digest that you sent 00:28:07.640 --> 00:28:09.079 is the same digest that I have. 00:28:09.400 --> 00:28:13.000 And so that's one way they can verify that they are speaking to the right devices 00:28:13.000 --> 00:28:14.680 in that particular environment. 00:28:14.680 --> 00:28:18.680 So if somebody comes along that's rogue, that is not using the right revision number, 00:28:18.680 --> 00:28:21.560 not using the right name, therefore, they're not using the right digest, 00:28:21.560 --> 00:28:22.359 they're going to be ignored. 00:28:23.640 --> 00:28:27.239 So you're only going to talk to those devices that have the same digest as you. 00:28:27.239 --> 00:28:30.920 So as you can see, there's a little bit of a safety feature added into this as well, 00:28:30.920 --> 00:28:34.920 unlike PVST+, or Rapid PVST+, where if you get a BPDU from anybody, 00:28:34.920 --> 00:28:37.959 you're just going to go ahead and agree with them because there's no way to verify 00:28:38.040 --> 00:28:39.800 that they're part of the same group as you. 00:28:39.800 --> 00:28:41.719 Whereas in this case, you are part of the same group. 00:28:43.640 --> 00:28:46.599 Now, you see this configuration information that we talked about earlier? 00:28:47.560 --> 00:28:49.880 Right, or all of this stuff here, I should say, let's just go out to here. 00:28:50.680 --> 00:28:54.359 Do show spanning tree MST configuration. 00:28:55.079 --> 00:28:57.640 All right, what I want you to realize is all of this information, 00:28:58.199 --> 00:29:01.959 you don't have to configure on every device. 00:29:01.959 --> 00:29:02.520 You don't. 00:29:04.040 --> 00:29:04.680 Why? 00:29:05.079 --> 00:29:05.719 Why? 00:29:05.719 --> 00:29:10.760 Because there's a way that you can auto-propagate this information to every other device. 00:29:12.839 --> 00:29:19.000 What service or protocol that we've already talked about, folks, 00:29:19.000 --> 00:29:24.359 do you think has the ability to allow you to configure it once 00:29:25.000 --> 00:29:29.479 and have it automatically propagated to every other switch in the environment? 00:29:30.119 --> 00:29:34.280 VTP version three, that's right. 00:29:34.280 --> 00:29:37.479 If you're using VTP version three, 00:29:38.760 --> 00:29:41.319 then VTP version three, you can set it up. 00:29:41.319 --> 00:29:46.040 So, anything you do with MSTP automatically gets sent to the other devices. 00:29:46.040 --> 00:29:50.520 So, you won't have to log into every other device and configure them yourself. 00:29:51.400 --> 00:29:53.640 All right, and that's why this message digest is really good. 00:29:53.640 --> 00:29:56.680 So, that way, when you are exchanging those messages dynamically 00:29:56.760 --> 00:30:00.920 and you're changing BPDUs dynamically, this helps as well, right? 00:30:00.920 --> 00:30:03.800 So, another thing to keep in mind, just for the real world, 00:30:03.800 --> 00:30:08.839 it may come up on the exam or not, but you do not send a BPDU for every single instance. 00:30:08.839 --> 00:30:13.079 So, even though I have three instances right now, I have zero, one, and two, 00:30:14.040 --> 00:30:19.959 we only send one BPDU, and we send one BPDU for instance zero. 00:30:19.959 --> 00:30:24.520 That's what we're sending, and we don't send a VLAN list or anything like that. 00:30:24.520 --> 00:30:25.000 Why? 00:30:25.000 --> 00:30:28.280 Because we send the digest instead, as I was talking about. 00:30:29.000 --> 00:30:31.160 So, we have instance zero. 00:30:31.719 --> 00:30:35.400 By default, all VLANs are mapped to instance zero, as we saw. 00:30:35.400 --> 00:30:37.479 So, if I just get out of the way here for a second, 00:30:38.280 --> 00:30:42.280 and you'll see that all the VLANs are originally mapped to instance zero, 00:30:42.280 --> 00:30:43.959 and then we have VLANs one and two. 00:30:43.959 --> 00:30:46.520 And I think we can see that if I scroll back up. 00:30:47.319 --> 00:30:49.079 When I was having those challenges, 00:30:49.160 --> 00:30:53.160 oh, I'm sure I typed it in, and we saw that they were all part of instance zero. 00:30:53.160 --> 00:30:55.160 I think it was on DSW two. 00:30:57.160 --> 00:30:58.199 Yeah, here is an example. 00:30:58.199 --> 00:31:00.839 So, this was before our config was finalized. 00:31:00.839 --> 00:31:04.680 You see how they're all mapped to instance zero by default. 00:31:04.680 --> 00:31:07.000 So, if you just wanted everything in one tree, 00:31:07.000 --> 00:31:09.400 you could just leave it in instance zero, and you're done. 00:31:09.959 --> 00:31:11.160 But if you want to get creative, 00:31:11.160 --> 00:31:14.359 then that's when you start breaking them out into other instances. 00:31:14.599 --> 00:31:18.040 So, when we send a BPDU, we're only sending it for IST. 00:31:18.040 --> 00:31:23.160 The IST, also known as instance zero, or MST instance zero. 00:31:23.160 --> 00:31:26.119 The name could be many different things, as you can see in my documentation here. 00:31:26.920 --> 00:31:32.439 And the IST, so this IST zero, this BPDU for the IST, 00:31:32.439 --> 00:31:37.079 carries all the Spanish-related information for itself. 00:31:37.079 --> 00:31:39.800 And it's just standard RST, but it's a standard RST. 00:31:39.800 --> 00:31:41.000 So, it's a standard RST. 00:31:41.160 --> 00:31:44.920 So, for itself, and it's just standard RSTP information. 00:31:44.920 --> 00:31:46.839 So, it's Rapid Spanish Protocol information. 00:31:48.920 --> 00:31:51.079 And then it has additional special fields 00:31:51.079 --> 00:31:53.560 that are going to be utilized as well to carry other information. 00:31:53.560 --> 00:31:57.079 For example, like we are going to have M records. 00:31:57.079 --> 00:31:58.920 So, for every other instance you have, 00:31:58.920 --> 00:32:02.839 you're going to have an M record associated with it. 00:32:02.839 --> 00:32:04.760 So, you have all the instance zero information, 00:32:04.760 --> 00:32:06.839 and then behind that, you have an M record for what? 00:32:06.839 --> 00:32:07.640 Instance one. 00:32:07.640 --> 00:32:09.640 You have an M record for instance two. 00:32:09.640 --> 00:32:14.199 So, for example, if you have DSW1 as the root bridge for instance one, 00:32:14.199 --> 00:32:16.920 then that M record would have that priority information in it. 00:32:16.920 --> 00:32:22.839 So, the bridge ID would be part of the M record for instance one. 00:32:22.839 --> 00:32:27.319 The bridge ID would be part of the M record for instance number two. 00:32:27.319 --> 00:32:32.199 So, those manipulations and changes you make to the specific instances, 00:32:32.199 --> 00:32:34.280 those are carried in the M records themselves, 00:32:34.280 --> 00:32:39.160 as well as other information that is very specific for those instances. 00:32:39.160 --> 00:32:42.520 Other than that, if there's nothing specific for those instances, 00:32:42.520 --> 00:32:45.239 then the information from instance zero applies. 00:32:45.239 --> 00:32:50.680 So, this ensures that you only have one BPDU going out every single interface, 00:32:50.680 --> 00:32:55.160 as opposed to one BPDU for each and every single tree, 00:32:55.160 --> 00:32:57.319 or as in our rapid Spanish tree protocol case, 00:32:57.319 --> 00:33:01.400 and Spanish tree protocol case, one for every single VLAN. 00:33:01.400 --> 00:33:04.520 So, you see the difference now in performance as well? 00:33:04.520 --> 00:33:06.520 There's a lot less pressure on our switches 00:33:06.520 --> 00:33:08.280 when we use multiple Spanish tree protocol 00:33:08.280 --> 00:33:10.040 because there's less BPDUs being sent, 00:33:10.040 --> 00:33:13.959 less BPDUs being received, and therefore processing is a lot better. 00:33:13.959 --> 00:33:17.160 Now, you have to be super careful here with multiple Spanish tree protocol, 00:33:17.160 --> 00:33:19.479 the last thing we're going to talk about for Encore. 00:33:19.479 --> 00:33:20.599 And what is that? 00:33:20.599 --> 00:33:24.040 It's the fact that you are now going to have to be careful 00:33:24.040 --> 00:33:27.400 with your trunk filtering and with your access ports. 00:33:27.959 --> 00:33:29.719 So, for example, let's say you have two switches, 00:33:30.599 --> 00:33:33.959 and this is VLAN 10 and this is VLAN 20. 00:33:34.920 --> 00:33:37.640 You have this set up for VLAN 10 and you have this set up for VLAN 20. 00:33:37.640 --> 00:33:41.239 So, access ports, this is not going to work for you. 00:33:42.199 --> 00:33:43.719 Why is this not going to work for you? 00:33:44.439 --> 00:33:47.880 Because Spanish tree protocol is looking at your instances 00:33:48.680 --> 00:33:51.719 when it's deciding whether to block or allow. 00:33:51.719 --> 00:33:59.400 So, if VLAN 10 is in instance number one, for example, 00:34:00.280 --> 00:34:04.439 and let's say VLAN 20 is also in instance number one. 00:34:05.239 --> 00:34:06.760 Say they're both in instance number one. 00:34:07.640 --> 00:34:10.040 Well, we have a loop here for instance number one, don't we? 00:34:10.679 --> 00:34:11.159 We do. 00:34:11.159 --> 00:34:12.040 Okay, let's block. 00:34:13.159 --> 00:34:18.120 Notice how VLAN 20 now is completely cut off on the network. 00:34:19.159 --> 00:34:21.080 So, what does that mean? 00:34:21.080 --> 00:34:25.399 It means you really can't use access ports between your switches at all 00:34:25.959 --> 00:34:27.320 when you're using MSTP. 00:34:29.320 --> 00:34:32.439 So, but when it comes to trunk ports now, so if you're using trunks, 00:34:33.399 --> 00:34:36.600 keep in mind that if you decide, oh, I'm going to filter, 00:34:36.600 --> 00:34:39.879 set up a VLAN filter in a trunk, 00:34:39.879 --> 00:34:44.600 and you're like, let's allow VLAN 10 here and let's allow VLAN 20 here. 00:34:44.600 --> 00:34:46.120 Well, again, you see the problem? 00:34:46.120 --> 00:34:49.639 Since they're both in instance one, if we block that trunk link, 00:34:50.760 --> 00:34:53.080 then you've just blocked VLAN 20 traffic. 00:34:53.080 --> 00:34:55.639 So, the moral of the story is that when it comes to filtering, 00:34:55.639 --> 00:34:58.439 you're going to have to make sure that your filtering 00:34:58.919 --> 00:35:05.239 for your VLANs is going to be equivalent to the VLANs that are in that instance. 00:35:05.239 --> 00:35:11.080 So, if you want to allow the VLANs, then you have to do allow 10, 20. 00:35:11.080 --> 00:35:13.000 Allow 10, 20. 00:35:13.000 --> 00:35:16.199 So, that way when this is blocked, you see everything works out perfectly fine. 00:35:17.159 --> 00:35:19.479 So, that's something to keep in mind when it comes to these. 00:35:19.479 --> 00:35:23.479 So, on the exam, if all of a sudden it's an MSTP example, 00:35:23.479 --> 00:35:26.600 and they have VLAN filtering on for trunks, 00:35:26.760 --> 00:35:30.120 and it's doing something like this, well, that's why you have a problem. 00:35:30.120 --> 00:35:31.719 That's why VLAN 20 is being cut off. 00:35:32.520 --> 00:35:36.760 It's because you have to remember that we're blocking on an instance by instance basis now, 00:35:36.760 --> 00:35:38.280 not a VLAN by VLAN basis now. 00:35:42.520 --> 00:35:44.360 So, a lot of good information there. 00:35:44.360 --> 00:35:47.479 The MSTP question shouldn't be very difficult on the certification exam. 00:35:48.679 --> 00:35:51.399 You're going to get more heavily tested on the other stuff we talked about today, 00:35:51.399 --> 00:35:56.040 but you know enough about MST to ace any question that shows up on the certification exam. 00:35:56.600 --> 00:35:57.100 Thank you.