1 00:00:00,330 --> 00:00:05,290 So let's look at rapid spending tree protocol or ADA 2.1 w. 2 00:00:06,200 --> 00:00:10,100 This is an evolution of the triple e ada 2.1 D standard. 3 00:00:10,130 --> 00:00:16,670 However, rapid spanning tree provides rapid failover and convergence times. 4 00:00:17,350 --> 00:00:24,160 The big difference that you need to remember here is that rapid spending tree is not based on timers 5 00:00:24,160 --> 00:00:34,120 like Ed or one RD, so it offers a improvement over the 32nd interval or longer that ed to one D takes 6 00:00:34,120 --> 00:00:37,360 to move a port to the forwarding state. 7 00:00:37,780 --> 00:00:43,570 What rapid spending tree does is it uses a bridge to bridge handshake mechanism, which allows ports 8 00:00:43,570 --> 00:00:47,950 to move directly to forwarding rather than waiting for the port. 9 00:00:47,950 --> 00:00:50,740 To move from listening to learning to forwarding. 10 00:00:53,110 --> 00:01:00,310 It is backward compatible with ADA 2 to 1 DD is transparent to end users and is standards based, but 11 00:01:00,310 --> 00:01:05,680 it does introduce some enhancements, including new port roll assignments and port states. 12 00:01:06,670 --> 00:01:10,000 A new BPD new format and BPD new processing. 13 00:01:10,270 --> 00:01:18,070 A bridge to bridge handshake mechanism and different topology change notifications and processing procedures. 14 00:01:20,120 --> 00:01:26,090 It's what our port states and port roles in 82 to 1 D and rapid spending tree. 15 00:01:26,540 --> 00:01:32,480 There are only three port states in rapid spending tree learning, forwarding and discarding. 16 00:01:32,810 --> 00:01:40,190 In ed one d we had disabled blocking and listening, and these have been merged into the discarding 17 00:01:40,190 --> 00:01:40,820 state. 18 00:01:41,330 --> 00:01:48,080 So when you administratively disable a port that's called disabled in eight or one D, but it's called 19 00:01:48,080 --> 00:01:55,160 discarding in inherited to one W or rapid spending tree, a blocking port that does not forward user 20 00:01:55,160 --> 00:02:02,930 data frames and ignores incoming data frames is called discarding an editor to 1wa listening port is 21 00:02:02,930 --> 00:02:10,160 not used and edited a1wa learning port is known as a learning port and a forwarding port is known as 22 00:02:10,160 --> 00:02:12,020 a forwarding port in 82 to 1. 23 00:02:12,020 --> 00:02:21,260 W So we have learning, forwarding and discarding disabled blocking and listening have been merged into 24 00:02:21,260 --> 00:02:22,670 the discarding state. 25 00:02:22,670 --> 00:02:28,820 In editor to one w Cisco still uses the term blocking for discarding. 26 00:02:28,820 --> 00:02:32,150 So just see those terms as interchangeable terms. 27 00:02:32,420 --> 00:02:35,150 Blocking is discarding and discarding is blocking. 28 00:02:35,570 --> 00:02:37,460 So what about port roles? 29 00:02:38,180 --> 00:02:41,870 The role is now a variable assigned to a given port. 30 00:02:41,960 --> 00:02:46,010 Previously we had root ports and designated ports and those remain. 31 00:02:46,010 --> 00:02:51,380 But blocking ports are now split into what are called backup and alternate port roles. 32 00:02:51,470 --> 00:02:58,220 Spanning three will determine the role of the port by looking at the BPD use received and deciding which 33 00:02:58,220 --> 00:03:00,590 one is more useful than another. 34 00:03:00,980 --> 00:03:08,270 A more useful BPD view is a BPD view that has a lower path cost or a better path to get to the root 35 00:03:08,270 --> 00:03:08,900 bridge. 36 00:03:11,020 --> 00:03:13,960 So let's start with a route put. 37 00:03:14,750 --> 00:03:16,460 With the spending tree protocol. 38 00:03:16,490 --> 00:03:22,490 The spending tree algorithm elects a single route bridge for the entire bridge network. 39 00:03:22,670 --> 00:03:24,170 Now with PVS DT. 40 00:03:24,200 --> 00:03:31,820 That's done on a per VLAN basis, but in ADA 2 to 1 DX or rapid spanning tree, there's only one route 41 00:03:31,820 --> 00:03:35,720 bridge or route switch for the entire layer two topology. 42 00:03:37,160 --> 00:03:43,250 The Route Bridge sends BP to use at a more useful than the ones sent by any other bridge. 43 00:03:43,550 --> 00:03:49,040 The port receiving the best BP due on a bridge or switch is known as the root port. 44 00:03:49,280 --> 00:03:54,890 In other words, this is the port that is closest to the Route Bridge in terms of path cost. 45 00:03:55,310 --> 00:04:00,980 So in this topology, if this switches the root switch, this port would be the root port of switch 46 00:04:01,050 --> 00:04:04,160 A and this would be the root port of switch B. 47 00:04:04,850 --> 00:04:07,610 The Route Bridge doesn't have a route port. 48 00:04:07,640 --> 00:04:10,700 All other bridges have at least one root port. 49 00:04:12,270 --> 00:04:14,040 What is a designated port. 50 00:04:14,340 --> 00:04:19,860 This is the best port on a segment to use to get to the root bridge. 51 00:04:20,160 --> 00:04:27,120 So all bridges connected to a given segment, listen to each other's BPD use and agree on the bridge, 52 00:04:27,120 --> 00:04:32,310 sending the best BPD view as the designated bridge for the segment. 53 00:04:33,710 --> 00:04:37,170 So in this topology, this switches the route. 54 00:04:37,190 --> 00:04:43,310 So for this segment, this is the designated port or best port to use to get to the Route Bridge. 55 00:04:43,490 --> 00:04:48,100 On this segment, this is the best port to use to get to the route bridge. 56 00:04:48,110 --> 00:04:50,120 So this is the designated port. 57 00:04:50,390 --> 00:04:55,940 Once again, just imagine that you've got a PC connected to the middle of this cable, which is the 58 00:04:55,940 --> 00:05:00,770 best way to get to the Route Bridge this way or this way. 59 00:05:01,100 --> 00:05:05,360 And as we can see, this is the best path or best way to get to the route bridge. 60 00:05:05,360 --> 00:05:06,800 So this is the route port. 61 00:05:07,040 --> 00:05:10,610 It's much quicker to go this way than it is to go this way. 62 00:05:10,760 --> 00:05:13,610 So this is the designated port on this segment. 63 00:05:13,610 --> 00:05:16,010 Let's assume that we've got a hub connected here. 64 00:05:17,200 --> 00:05:23,950 This port has been chosen as the designated port, and that may be because the switch here has a lower 65 00:05:23,950 --> 00:05:29,540 bridge ID than switch A and this is port one, which is lower than port two. 66 00:05:29,560 --> 00:05:32,650 So this is the designated port on that segment. 67 00:05:34,510 --> 00:05:37,210 Now what about alternate and backup patrols? 68 00:05:37,420 --> 00:05:41,530 These correspond to the blocking state in 2 to 1 D. 69 00:05:41,560 --> 00:05:46,750 A blocked port is defined as any port that is not a designated or route port. 70 00:05:47,050 --> 00:05:50,740 A port remains blocked as long as it receives more useful. 71 00:05:50,740 --> 00:05:56,020 In other words, better BPT use than the one it would send out on the segment. 72 00:05:56,140 --> 00:06:00,490 Therefore, Port must receive BPD use in order to stay blocked. 73 00:06:00,580 --> 00:06:05,650 If it doesn't receive BPD use, it will transition to the forwarding state. 74 00:06:06,130 --> 00:06:09,280 So in rapid spanning tree there are two types of blocked ports. 75 00:06:09,520 --> 00:06:16,720 An alternate port is a port that is blocked because it's receiving more useful BPD use from another 76 00:06:16,720 --> 00:06:18,490 bridge on the segment. 77 00:06:18,910 --> 00:06:25,720 So in this example, this port is the designated port on let's say switch B on, switch A, this port 78 00:06:25,720 --> 00:06:34,300 is an alternate port because more useful or better BPAs are being received on this segment from Switch 79 00:06:34,300 --> 00:06:40,390 B, then from switch A, and that may be because the priority of switch B is lower than the priority 80 00:06:40,390 --> 00:06:41,200 of Switch A. 81 00:06:42,040 --> 00:06:49,300 A backup port is a port that is blocked because it's receiving more useful BPD use from the same bridge 82 00:06:49,300 --> 00:06:50,200 that it's on. 83 00:06:50,500 --> 00:06:56,920 So in this example, we're assuming that this port, this port and this port are connected to a hub. 84 00:06:56,980 --> 00:06:59,440 This port becomes the backup port. 85 00:06:59,650 --> 00:07:06,340 It's connected to the same switch as this designated port, but it may be a higher port number. 86 00:07:06,370 --> 00:07:08,830 Therefore, it becomes the backup port.