1 00:00:00,700 --> 00:00:07,740 On point to point links a proposal agreement handshake sequences used by rapid spending tree to achieve 2 00:00:07,740 --> 00:00:15,360 fast convergence so rapid spending he uses this to quickly transition ports to the fording state where 3 00:00:15,360 --> 00:00:22,800 as a two to one D was just waiting for timer's to expire before ports were set to the forwarding state 4 00:00:23,280 --> 00:00:31,800 in this apology the link between the router switch on port 0 and port one on the switch came up they 5 00:00:31,800 --> 00:00:34,390 would send proposals to each other. 6 00:00:34,590 --> 00:00:42,480 Both ports are put into designated blocking and they both send a rapid spending tree BPT with a proposal 7 00:00:42,510 --> 00:00:43,790 but set. 8 00:00:43,920 --> 00:00:49,650 Now this relies on a new BPU format which contains a proposal. 9 00:00:49,650 --> 00:00:51,650 But in the BPT. 10 00:00:51,990 --> 00:00:56,830 So additional information in a rapid spinning tree BPT you be noted. 11 00:00:57,120 --> 00:01:03,930 We have the proposal but we have the port roll we have learning forwarding and agreement butts as well 12 00:01:03,930 --> 00:01:07,230 as a topology change but and topology change acknowledgement. 13 00:01:07,230 --> 00:01:12,020 But that are part of the rapid spending tree BPU. 14 00:01:12,120 --> 00:01:17,760 So essentially what happens is when the port comes up the switches send proposals to each other saying 15 00:01:18,090 --> 00:01:23,130 I want to have the designated port on the segment. 16 00:01:23,130 --> 00:01:31,170 However because bridgeway this switch here receives a BPT you indicating a superior Poth cost. 17 00:01:31,170 --> 00:01:39,270 In other words a better path is found via the route switch then itself it immediately knows that port 18 00:01:39,270 --> 00:01:41,310 1 is going to be its new route port. 19 00:01:41,490 --> 00:01:47,520 So know straight away that this port should be its route port because this port has the best path back 20 00:01:47,580 --> 00:01:48,450 to the route switch. 21 00:01:48,450 --> 00:01:54,860 In other words a superior or better or lower path cost bridge a. 22 00:01:54,870 --> 00:02:01,290 In other words the switch starts a sync to ensure that all of its ports are in sync with this new information. 23 00:02:01,290 --> 00:02:04,750 A port is in sync if it meets the following criteria. 24 00:02:04,770 --> 00:02:06,060 It isn't the blocking state. 25 00:02:06,060 --> 00:02:09,740 In other words it's discarding What's an H port. 26 00:02:09,770 --> 00:02:17,660 So in this example port 2 is an alternate port Port 3 is a designated port and port 4 is a large port 27 00:02:18,260 --> 00:02:22,490 support to and port for a ready meet. 28 00:02:22,490 --> 00:02:29,270 One of the criteria listed above it's in the blocking state or it's an edge port so to be in sync bridge 29 00:02:29,300 --> 00:02:35,180 a must block port three and assigns it to the discarding state. 30 00:02:35,180 --> 00:02:41,660 Now that all ports are in sync bridge a can unblock its newly selected route port and reply to the route 31 00:02:41,660 --> 00:02:44,060 with an agreement message. 32 00:02:44,080 --> 00:02:52,000 So basically a proposal is sent from the route to switch a switch a agrees that this is the best path 33 00:02:52,000 --> 00:02:53,290 back to the route. 34 00:02:53,320 --> 00:02:59,200 It blocks all ports or make sure that they are in sync because they edge ports and then sends back an 35 00:02:59,200 --> 00:03:01,420 agreement as soon as that happens. 36 00:03:01,420 --> 00:03:08,440 The ports can be unblocked so bridgeway can block its port and replies with an agreement message. 37 00:03:08,440 --> 00:03:13,810 Once the route switch receives that agreement message it can transition immediately to the forwarding 38 00:03:13,810 --> 00:03:14,450 state. 39 00:03:14,780 --> 00:03:18,390 So proposal agreement unblock port. 40 00:03:18,400 --> 00:03:21,340 In other words set it to the forwarding state. 41 00:03:21,370 --> 00:03:23,390 Now that happens very very quickly. 42 00:03:23,650 --> 00:03:28,870 Now by the same token switch a can send a proposal to the switch. 43 00:03:29,030 --> 00:03:30,530 So this process continues. 44 00:03:30,680 --> 00:03:32,050 Proposal to the switch. 45 00:03:32,210 --> 00:03:33,990 The switch sends back an agreement. 46 00:03:34,040 --> 00:03:36,260 This port can go to the forwarding state. 47 00:03:36,260 --> 00:03:40,170 This happens very quickly because it doesn't rely on timers. 48 00:03:40,250 --> 00:03:46,400 This wave of hand-shakes propagates quickly towards the edge of the network and quickly restores connectivity 49 00:03:46,550 --> 00:03:48,720 after a change in the topology. 50 00:03:48,890 --> 00:03:55,760 If a designated discarding port does not receive an agreement to its proposal it slowly transitions 51 00:03:55,760 --> 00:03:59,810 to the forwarding state using the traditional Ada to the one d. 52 00:03:59,810 --> 00:04:02,020 Listening learning sequence. 53 00:04:02,300 --> 00:04:08,570 This could happen if the remote bridge doesn't understand Reppert spending three BPT use with them remote 54 00:04:08,870 --> 00:04:11,090 bridges port is blocking. 55 00:04:11,090 --> 00:04:20,850 So an apology at the moment shows spanning tree gigabit 0 1 is a designated port in the fording state 56 00:04:20,880 --> 00:04:23,460 but it's a shared port. 57 00:04:23,660 --> 00:04:26,740 In this topology gigabit 00 has been shut down. 58 00:04:26,990 --> 00:04:33,910 So the root port on switch 3 gigabit is 0 1 and the alternate port is gigabit 0 2. 59 00:04:34,070 --> 00:04:46,220 But if I know shut gigabit 00 so I'd be unable to support again show spending tree noticed gigabit 00 60 00:04:46,580 --> 00:04:49,660 is the root port of switch 3. 61 00:04:49,670 --> 00:04:53,440 This port is now the designated port but is in a blocking state. 62 00:04:53,540 --> 00:05:04,210 0 2 is in the blocking state backup port on switch to the status has changed to blocking because on 63 00:05:04,210 --> 00:05:09,500 this segment this is the base pool to use to get back to the root bridge. 64 00:05:09,550 --> 00:05:15,610 However it takes longer for this process to complete than it would be if it was a point to point link 65 00:05:16,030 --> 00:05:18,060 shit porch take longer to converge. 66 00:05:18,310 --> 00:05:19,850 So let's do that again. 67 00:05:20,050 --> 00:05:24,800 Shut the port so gigabit to 0 0 is not going to be shut down. 68 00:05:27,280 --> 00:05:30,990 Previously gigabit zero or one on the switch was the old tenant port. 69 00:05:31,000 --> 00:05:35,550 Now it's the designated port but it's blocking still blocking 70 00:05:38,440 --> 00:05:47,320 show spinning tree on switch three is alternate port is blocking route Portas forwarding. 71 00:05:47,540 --> 00:05:49,350 Now the port is in the learning state. 72 00:05:49,430 --> 00:05:54,040 So traffic is still being dropped on this port even though this is the port to use to get to the root 73 00:05:54,050 --> 00:05:54,560 bridge. 74 00:05:56,260 --> 00:06:03,970 Now it's fording can take 30 seconds on a shared port because we using traditional Ada to the one d 75 00:06:04,310 --> 00:06:12,750 listening learning sequences on that port to use proposals and agreements the ports need to be configured 76 00:06:12,750 --> 00:06:17,340 as point to point ports or need to negotiate to use full duplex.