Welcome to Jeremy’s IT Lab. This is a free, complete course for the CCNA. If you like these videos, please subscribe to follow along with the series. Also, please like and leave a comment, and share the video to help spread this free series of videos. Thanks for your help. Also, remember to download this practice lab from the link in the video description and try it out yourself in packet tracer. If you want more labs like these, I highly recommend picking up Boson’s NetSim for the CCNA, click the link in the video description to check it out. It’s a network simulator like packet tracer, but it’s even better, and it includes all of these guided labs to not only help you get hands-on practice configuring and troubleshooting, but also deepen your understanding of the exam topics. I used it myself when studying for my certifications, so I feel confident about recommending it to all of you. Watch until the end of this video for a preview of a lab from NetSim. And if you want to get your own copy of NetSim, please follow the link in the video description. Okay, in the lab instructions for today’s lab, I mention that you should turn off link lights in packet tracer. That’s because, if you can see the link lights, you will know which interfaces are in a forwarding state and which are in a blocking state. To turn them off, which I already have, click on options up here, then preferences, then make sure ‘show link lights’ is disabled. By the way, I assume you’ve already studied and understood the process I taught in the lecture video, so this will just be a fairly quick walkthrough. If you have forgotten some concepts, like bridge ID, root cost, etc, please watch the lecture video again to review before trying this exercise. So, the first portion of this lab is the same as the practice quiz questions we did at the end of the lecture video. Identify the root bridge, then identify the spanning tree port role of each switch interface, either root, designated, or non-designated. But since we’re in Packet Tracer, we can now use the CLI to confirm our answers. I didn’t want to make the lecture video too long so I didn’t show any CLI commands so please watch this video to see which commands you can use to confirm spanning tree. First up, which switch is the root bridge? First we must compare the bridge priorities, and if there is a tie, compare the MAC addresses. Those are the two components of the spanning tree bridge ID, and the switch with the lowest bridge ID becomes the root bridge. In this case the answer is fairly obvious, SW3 has the lowest priority, 24577, so it will be the root bridge. So, we now know port role of each interface on SW3, all of its interfaces must be designated ports because it is the root bridge. Just to make things easier to remember, let me make labels. Click on the note button up here, and let me make 4 Ds, for designated. Okay, and after you have made them let’s move them into position. Okay, so all four interfaces on SW3 are designated ports. Next up, let’s find the root ports. Each other switch in the topology must have a single root port. The first criteria to determine the root port is the root cost, the interface with the lowest root cost will become the root port. How about SW1? Via either F0/1 or F0/2 it would have a cost of 19, plus 4 for SW1’s G0/1, and plus 4 for SW4’s G0/2, so 27. Via f0/3 or f0/4 it has a cost of just 19. So, it will be either F0/3 or F0/4, but we don’t know which so let’s look at the tiebreaker, neighbor bridge ID. Well, both are connected to the same switch, SW3, so that is a tie as well. The final tie breaker is the neighbor switch’s port ID, the lowest one wins. It’s important to remember that this isn’t the LOCAL switch’s port ID, it’s not SW1’s port ID. It’s the neighbor switch’s port ID, SW3’s port ID. F0/1 is lower, so that means SW1’s F0/4 interface will be the root port, let me create that label. And then I will move it over to SW1. Okay next, which will be SW2’s root port? F0/3 is directly connected to the root bridge, so it might look obvious that this will be the root port, however via F0/3 it has a root cost of 19. Via G0/1 it has a root cost of 4, plus 4 for SW4’s G0/2, so only 8. Therefore, G0/1 will be the root port. That also means we can label SW4’s G0/1 interface as designated, the interface connected to a root port is always designated. So, SW4’s root port is now obvious, since G0/1 is designated, it’s other port, G0/2, must be the root port. It also has a very low cost, only 4. Okay, so we have found and labeled all of the root ports. Next up, in each remaining collision domain we must determine which side will be designated and which will be non-designated. First up, two very obvious ones. SW1’s F0/3 is connected to the root bridge, so it must be non-designated. The same goes for SW2’s F0/3, it is connected directly to SW3, so it is non-designated. SW3's port is already designated. All that remain are F0/1 and F0/2 on SW1 and SW2. The first criteria is the root cost. The interfaces on the switch with the lower root cost will be designated, the other side will be non-designated. SW1's root cost is 19, via F0/4. However SW2’s root cost is 8 via G0/1. So, SW2 has the lower root cost, therefore its F0/1 and F0/2 interfaces will both be designated. The other side, SW1’s F0/1 and F0/2, will both be non-designated, in a blocking state. Now that we’ve figured out the answers, let’s actually check by using the CLI. Let’s go on the root bridge, SW3 first. So enter privileged exec mode with ENABLE. And the first command I want to show you is SHOW SPANNING-TREE. At the top here, it shows the VLAN number. If there were multiple VLANs on these switches, you would see all of this information listed separately for each VLAN. In fact you can filter the output of this command to show a single VLAN like this, SHOW SPANNING-TREE VLAN 1. But we only have a single VLAN, so it doesn’t matter here. Under that, spanning tree enabled protocol IEEE. This means we are using the ‘classic’ spanning tree. Actually, it’s Cisco’s PVST, but this means it’s in ‘classic’ mode rather than the newer rapid spanning tree, which we will look at in a future video. Then there are two big sections, Root ID, which lists information about this spanning tree’s root bridge, and bridge ID, which lists information about this switch’s information. In this case, SW3 IS the root bridge, so they are the same, with a few differences in the information they present. Under Root ID it just lists the priority of 24577, but down here it shows that really its the priority of 24576 plus the extended system ID of 1, for VLAN 1. In the root ID section it clearly states, this bridge is the root. Then there are some timers listed, I’ll talk about these timers in the next lecture video. Finally, at the bottom, each interface participating in spanning tree is listed, you can see the role, status, cost, interface ID, and interface type, and I won't talk about the interface type in this course by the way, it's not necessary. So, because this is the root bridge, we expect all interfaces to be designated ports and to be forwarding. As you can see, they are, so we were correct. Now, before moving to another switch, let me briefly show another couple commands. SHOW SPANNING-TREE DETAIL lists similar information to SHOW SPANNING-TREE, but as you might expect, with more details. I won’t go through everything here, but feel free to take a look if you want. And one more command, SHOW SPANNING-TREE SUMMARY. This lists each VLAN, and shows how many interfaces are in each STP state. I told you about Blocking and Forwarding already, but these two here, listening and learning, are transitional states which I will teach you about in the next video. The final column, STP active, just lists how many interfaces are STP activated in total. By default, every interface that is connected to another device and enabled will have STP running. Next let’s take a look at SW1. Enter privileged exec mode with ENABLE. SHOW SPANNING-TREE. As expected, F0/4 is the root port and is forwarding, and the other interfaces are blocking. Note that slightly different terminology is used here, ‘alternate’ instead of non-designated, but the meaning is the same. Also, notice that the root ID section shows SW3’s information, but now the bridge ID information is different, this is SW1’s own information. So, our answers for SW1 were correct. Next up, let’s go to SW2. ENABLE. SHOW SPANNING-TREE. Looks like we were correct again. F0/1 and F0/2, connected to SW1, are both designated and in a forwarding state, although really these connections are disabled because SW1 is blocking those ports. F0/3 is blocking, and G0/1 is the root port. By the way, something I should have mentioned before, the COST displayed here is just the cost of this interface, not the total root cost, so it only displays 4 here. If you want to see the total root cost, use this command I showed you. SHOW SPANNING-TREE DETAIL. Here it says, cost of root path is 8, because there are two gigabit ethernet interfaces in the path. Finally, let’s check on SW4. ENABLE. SHOW SPANNING-TREE. So, G0/1 is designated, and G0/2 is the root port. So, we successfully calculated the spanning tree topology. That’s all for this lab. Next up, let’s take a look at a lab in Boson NetSim. Okay, for today's Boson NetSim for CCNA lab preview I will once again do something a little bit different. Here in the 'network access' section of NetSim for CCNA, you'll notice there are no labs for spanning tree. Why is that, why does Boson not include spanning tree in NetSim for CCNA? Well, let's check the exam topics list. These are the exam topics for the CCNA 200-301, current version. 2.5, 'describe the need for and basic operations of rapid PVST+ spanning tree protocol and identify basic operations.' So, 'describe' and 'identify'. There's no mention of 'configure', like these other topics. 'Configure, configure, configure, configure.' This one, 'describe' and 'identify'. So, according to the exam topics list, spanning tree configuration is not on the CCNA exam. So that's probably why Boson didn't include it in NetSim for CCNA. However I still think it's a good idea to get some hands-on practice in the CLI, observing and configuring spanning tree. So that's why I include labs in my course. However, if you check out the CCNP ENCOR 350-401 exam topics list, here. 3.1c, configure and verify common spanning tree protocols. So configuration is included in the CCNP exam topics list. So instead of a CCNA, NetSim for CCNA lab, let's do a NetSim for CCNP ENCOR lab. There are quite a few spanning tree labs here. Starting here, 'Spanning Tree 1', all the way down to here, 'Implementing Multiple Spanning Tree Protocol.' The one we're going to take a look at today is this one, simply titled 'Spanning Tree Protocol'. Click on the lab, and click 'load lab'. But, I've already done that, so 'lab instructions'. So there are four switches here, P1ASW1, ASW2, P1DSW1, DSW2. ASW mean 'access switch', 'access layer switch'. And DSW is 'distribution layer switch'. These are two common layers of network design, good network designs, and I haven't actually talked about them yet in my course. So, you can wait for that in the future. Just know their meaning now, 'access switch', 'distribution switch'. Notice the hosts connect to the access switches, and then the access switches connect to the distribution switches. Okay, so just for today's preview I will do this step here, step 1. On P1DSW1, issue the SHOW SPANNING-TREE VLAN 1 DETAIL, I just showed you this command, SHOW SPANNING-TREE DETAIL, to display the spanning tree for VLAN 1. Use the output to answer the following questions. So let's go into the CLI of DSW1 here. Click on the device and click on 'console'. Okay, and we're in. ENABLE. SHOW SPANNING-TREE VLAN 1 DETAIL. Okay. So, question A, which spanning tree is VLAN 1 executing? We aren't actually going to do any configuration in this step, by the way, this is just answering questions. And actually that's something I really like about NetSim, they ask you good questions to really test your understanding of the topic. So anyway, which spanning tree? It says it right here, 'VLAN 1 is executing the ieee compatible Spanning Tree Protocol'. This means classic spanning tree protocol, the one I taught you in the lecture video. This is not rapid spanning tree protocol. Okay, so that's the answer, regular classic spanning tree. B, what are the priority, sys-id, this is the extended system ID, the VLAN number, and MAC address. They are stated here. Bridge identifier, bridge ID, has priority 24576, sysid 1, which actually gets added to the priority so it's really 24577 in total. And this is the MAC address. So, that's question B. Why is there no root port? Well let's confirm, is there a root port? Here, fastethernet0/1 is designated forwarding, so it's not a root port, it's a designated port. 0/2 designated, 0/3 designated, designated, designated, and designated. So there are in fact no root ports. Why is that? Well, the answer is here. We are the root of the spanning tree. This switch is the root bridge. As you know, every port, every interface on the root bridge must be designated. So that's why there are no root ports. So that's C. And then D, why are there no blocked ports for VLAN 1? Well that's the same reason, because it's the root. There will be no blocked ports on the root bridge, they should all be designated ports in a forwarding state. Okay, E, what is the timer value for sending BPDUs, bridge protocol data units? So, I haven't talked about the timers yet in the lecture video, so I will talk about them in the next lecture video, Day 21. But the answer is here. Configured hello time. Hello time is the interval at which it sends those BPDUs, they're called 'hello BPDUs'. So 2 means 'every 2 seconds'. So it will send 1 BPDU every 2 seconds. What is the maximum age for a BPDU? Here it is, 20 seconds. Again, I will talk about this, this maximum age timer, in the next video. And what is the value of the forward delay timer? It is 15 seconds. Sorry, there we go. 15 seconds. These are the defaults. 2, 20, 15. Okay, so that's the answer for G. Okay, so there is one more step here to this lab, and then lab solutions highlighting all of the different outputs you can see, pretty much everything we just looked at. Yeah, okay. So there it is, Boson NetSim. If you want to get a copy of Boson NetSim for CCNA, and I highly recommend you do, look at all of these guided labs they have here for all the exam topics. From network fundamentals, network access, IP connectivity, IP services, security fundamentals. So if you can I highly recommend getting a copy of NetSim for CCNA. If you want a copy, please follow the link in the video description. Thank you for watching. Please subscribe to the channel, like the video, leave a comment, and share the video with anyone else studying for the CCNA. If you want to leave a tip, check the links in the description. I'm also a Brave verified publisher and accept BAT, or Basic Attention Token, tips via the Brave browser. That's all for now.