1 00:00:00,750 --> 00:00:05,700 In this topology, I have two switches which are configured to run PVS. 2 00:00:05,700 --> 00:00:09,870 RT Not rapid PVS plus, but simply PVS. 3 00:00:10,650 --> 00:00:12,450 I'll show you that config in a moment. 4 00:00:12,480 --> 00:00:17,790 Rather, one is connected to switch one and router two is connected to switch two, and the routers 5 00:00:17,790 --> 00:00:23,400 are simply acting as edge devices or PCs in this topology. 6 00:00:23,970 --> 00:00:27,120 I've also got a hub connected to switch one and switch to. 7 00:00:28,000 --> 00:00:33,100 His switch one show run pipe include. 8 00:00:34,600 --> 00:00:35,680 Span. 9 00:00:37,760 --> 00:00:41,120 As you can see at the moment, the switch is configured for PV ist. 10 00:00:42,050 --> 00:00:45,200 I'll explain the extended system ideas in more detail later. 11 00:00:45,380 --> 00:00:52,260 But essentially it means that the priority of the switch is based on the priority and VLAN number. 12 00:00:52,280 --> 00:00:54,410 So as an example, show spanning tree. 13 00:00:55,340 --> 00:01:05,060 The switch has a bridge ID consisting of the property 32769, which is the default of 32768 plus the 14 00:01:05,060 --> 00:01:11,870 extended system ID of one because we're looking at a VLAN one and MAC address of the following. 15 00:01:12,080 --> 00:01:14,360 The switch is currently the route. 16 00:01:14,690 --> 00:01:20,450 What I want you to see is that the spanning tree enabled here is a triple E. 17 00:01:20,570 --> 00:01:26,270 So in this output it looks like you're running at a 2 to 1 dx, but actually the switch is configured 18 00:01:26,270 --> 00:01:34,880 for per VLAN, spanning tree per VLAN, spanning tree is compatible with ADA 2 to 1 DX switches and 19 00:01:35,000 --> 00:01:37,820 therefore we can see triple E in the output here. 20 00:01:38,930 --> 00:01:40,130 His switch to. 21 00:01:42,370 --> 00:01:45,550 So run pipe include span. 22 00:01:47,630 --> 00:01:49,940 Switches configured to use PV ist. 23 00:01:51,130 --> 00:01:54,040 Extended system IDs are being used. 24 00:01:57,780 --> 00:01:58,590 On the switch. 25 00:01:58,590 --> 00:02:04,170 The bridge ID consists of the property three, two, seven, six and nine, which is 32768. 26 00:02:04,200 --> 00:02:10,320 The default plus the VLAN number, which is VLAN one in this example. 27 00:02:10,650 --> 00:02:13,200 This is the MAC address of the switch. 28 00:02:13,530 --> 00:02:16,500 So we have two switches. 29 00:02:16,740 --> 00:02:18,510 One has this MAC address. 30 00:02:18,750 --> 00:02:20,820 One has this Mac address. 31 00:02:21,210 --> 00:02:21,710 Switch. 32 00:02:21,720 --> 00:02:30,450 One has become the root of the spanning tree because it has a lower Mac address when compared to the 33 00:02:30,450 --> 00:02:31,110 switch. 34 00:02:31,320 --> 00:02:40,350 So because of the Lower Mac address notice AC is lower than E in hexadecimal switch one became the root 35 00:02:40,350 --> 00:02:41,640 of the spanning tree. 36 00:02:42,590 --> 00:02:48,560 What you'll also notice is that on switch one, all ports are forwarding in the topology. 37 00:02:48,710 --> 00:02:53,600 The ports that are currently connected are those ports and they all forwarding. 38 00:02:54,820 --> 00:03:03,190 On switch to however port one which is gigabit is zero zero is the root port and its forwarding has 39 00:03:03,190 --> 00:03:05,610 a path cost of four gigabit. 40 00:03:05,680 --> 00:03:14,920 Zero one is blocking or discarding to use the industry standard term port two is forwarding. 41 00:03:15,770 --> 00:03:19,280 Port three is blocking. 42 00:03:19,400 --> 00:03:25,880 So this port is also blocking route switches forward on all ports. 43 00:03:26,420 --> 00:03:31,520 Before I show you how port status is were determined, let's have a look at the beads. 44 00:03:33,790 --> 00:03:42,490 So to start a CAPTCHA on that link and what we can see here in Wireshark is a spanning tree BPU. 45 00:03:42,700 --> 00:03:46,960 So it's using 82.3 Ethernet frames. 46 00:03:47,320 --> 00:03:51,460 Notice the destination address is the well-known MAC address for Spanning Tree. 47 00:03:53,040 --> 00:03:58,140 It is a multicast broadcast address from this Mac address. 48 00:03:58,560 --> 00:03:59,120 Yes. 49 00:03:59,130 --> 00:04:00,120 Which one? 50 00:04:00,150 --> 00:04:12,780 Notice the MAC address of the switch is zero zero 11 C six ac d d and we currently looking at port three 51 00:04:12,780 --> 00:04:13,620 on the switch. 52 00:04:13,800 --> 00:04:18,269 So notice d00, but this is dd03. 53 00:04:18,750 --> 00:04:23,760 Because in spanning three, that's the port that we currently looking at. 54 00:04:24,090 --> 00:04:27,960 If we went and looked at Port two as an example. 55 00:04:32,630 --> 00:04:35,120 Notice the Mac address ends in zero two. 56 00:04:35,340 --> 00:04:39,140 We've got port 000102 and zero three. 57 00:04:39,500 --> 00:04:41,360 So back in Wireshark. 58 00:04:42,380 --> 00:04:45,170 He has a capture sent out of Port three. 59 00:04:46,820 --> 00:04:47,780 In spending tree. 60 00:04:47,780 --> 00:04:49,700 We can see the spending tree version. 61 00:04:49,970 --> 00:04:56,570 So this is spending tree is zero because in this port it's actually using ADA 2 to 1 DX or the original 62 00:04:56,570 --> 00:04:57,860 version of Spending Tree. 63 00:04:58,710 --> 00:05:01,740 The root identifier is 32768. 64 00:05:01,770 --> 00:05:06,300 There's the VLAN number and there's the MAC address of the switch. 65 00:05:06,930 --> 00:05:09,000 Which we can see clearly here. 66 00:05:09,450 --> 00:05:11,970 So notice route identifier. 67 00:05:12,810 --> 00:05:15,210 There's the information of 32768. 68 00:05:15,510 --> 00:05:16,680 VLAN one. 69 00:05:16,860 --> 00:05:19,380 There is the mac address of the switch. 70 00:05:20,010 --> 00:05:23,550 The route path cost is zero because this switch is the route. 71 00:05:23,550 --> 00:05:26,280 So there's no cost to get to the route. 72 00:05:26,670 --> 00:05:32,730 There's the port identifier and here are some timers used in spanning tree. 73 00:05:33,000 --> 00:05:37,290 Now when a switch boots up, all ports are put into the blocking state. 74 00:05:37,590 --> 00:05:43,080 They then move to other states based on timers in a 2 to 1 D. 75 00:05:44,540 --> 00:05:49,010 When a spending tree switch boots up, all ports are put into the blocking state. 76 00:05:49,460 --> 00:05:55,460 After 20 seconds called the max age timer, ports move to what's called the listening state. 77 00:05:55,910 --> 00:06:01,460 If a switch is already up and you connect a cable to the port, in other words, the link goes up. 78 00:06:01,610 --> 00:06:03,680 It starts at the listening state. 79 00:06:03,710 --> 00:06:07,280 Ports will then move to the learning state. 80 00:06:08,530 --> 00:06:15,610 Based on the forward delay, which is 15 seconds in duration and after 15 seconds, ports transition 81 00:06:15,610 --> 00:06:18,070 from the learning state to the forwarding state. 82 00:06:18,370 --> 00:06:26,110 So an editor of one RD or PVS ist, it can take 50 seconds for ports to start forwarding on switches 83 00:06:26,320 --> 00:06:30,040 because they move from blocking to listening to learning to forwarding. 84 00:06:30,280 --> 00:06:36,190 Now in the listening state they are sending beep to use but not updating their mac address tables. 85 00:06:36,340 --> 00:06:44,050 In the learning state beeps are sent and the MAC address tables of switches are updated, so only if, 86 00:06:44,050 --> 00:06:48,640 based on the spanning tree calculation, it's determined that a port can be opened. 87 00:06:48,970 --> 00:06:56,140 A port is set to the forwarding state after 50 seconds when a switch comes up, or typically if a switch 88 00:06:56,140 --> 00:07:03,730 is already up and you plug an A cable into that switch after 30 seconds, the port will start forwarding. 89 00:07:04,120 --> 00:07:10,360 So in the BPD queue we can see the max age timer and the forwarding delay timer. 90 00:07:10,390 --> 00:07:14,110 This is determined by the route bridge. 91 00:07:14,350 --> 00:07:19,240 So on switch one, which is the route bridge, we can see that the hello timer. 92 00:07:19,240 --> 00:07:23,380 In other words, BPU hellos are sent out every 2 seconds. 93 00:07:23,380 --> 00:07:29,920 The max age time is 20 seconds and the forwarding delay timer is 15 seconds. 94 00:07:30,660 --> 00:07:36,150 And that's what we see in the BPAs as captured in our topology.