1 00:00:00,700 --> 00:00:08,860 So how is this rapid convergence or rapid transition to forwarding state accomplished in a 2 to 1 W 2 00:00:08,890 --> 00:00:10,150 or rapid spanning tree? 3 00:00:10,780 --> 00:00:14,170 This is one of the most important features introduced in rapid spanning tree. 4 00:00:14,260 --> 00:00:16,940 The difference is that a legacy spanning tree. 5 00:00:16,960 --> 00:00:23,560 In other words, the legacy spanning tree algorithm passively waited for the network to converge before 6 00:00:23,560 --> 00:00:26,350 moving a port into the forwarding state. 7 00:00:26,650 --> 00:00:33,880 Achieving foster convergence was a matter of tuning the conservative default parameters of forward delay 8 00:00:33,880 --> 00:00:35,410 and max age timers. 9 00:00:36,160 --> 00:00:42,840 So in the past you would try and manipulate these timers to get spanning tree to converge quicker. 10 00:00:42,850 --> 00:00:47,860 But this often resulted in the sacrificing of network stability. 11 00:00:47,980 --> 00:00:54,460 Rapid spanning tree is able to actively confirm that a port can safely transition to forwarding without 12 00:00:54,460 --> 00:00:57,850 relying on any timer configuration. 13 00:00:57,880 --> 00:00:59,160 That's the big difference. 14 00:00:59,170 --> 00:01:01,060 It doesn't rely on timers. 15 00:01:01,090 --> 00:01:08,200 There is a negotiation between the switches on point to point lengths to allow them to converge quicker. 16 00:01:08,530 --> 00:01:13,180 So there's a feedback mechanism that operates between rapid spanning tree compliant bridges. 17 00:01:13,480 --> 00:01:20,230 To achieve foster convergence, you need to configure edge ports and links between switches need to 18 00:01:20,260 --> 00:01:22,180 become point to point lengths. 19 00:01:22,240 --> 00:01:26,920 Now an edge port is essentially the same as port first ports. 20 00:01:27,040 --> 00:01:29,920 They transition immediately to the forwarding state. 21 00:01:30,160 --> 00:01:37,270 This is to allow in stations to skip the listening and learning stages in spanning tree convergence 22 00:01:37,450 --> 00:01:43,050 and edge port also does not generate topology changes when its link toggles. 23 00:01:43,060 --> 00:01:48,070 So in other words, when a link goes down or comes up and it's configured as an edge port or a port 24 00:01:48,070 --> 00:01:52,300 first port, it doesn't cause the network topology to recalculate. 25 00:01:53,200 --> 00:01:59,770 Unlike Port Foster, though, and each port that receives a beep due immediately loses its edge port 26 00:01:59,770 --> 00:02:06,820 status and becomes a normal spanning report that is a built in security mechanism to stop someone accidentally 27 00:02:06,820 --> 00:02:14,530 plugging in a switch or a hub into a port first port and causing a loop in Cisco's implementation. 28 00:02:14,560 --> 00:02:20,410 The port first command is used for edge port configuration, thus making the transition to rapid spanning 29 00:02:20,410 --> 00:02:21,220 tree simpler. 30 00:02:21,250 --> 00:02:26,470 In a separate video, I'll show you the configuration and testing of Port First Ports. 31 00:02:26,920 --> 00:02:30,130 I've already demonstrated how to set up a point to point link. 32 00:02:30,400 --> 00:02:35,890 This is automatically determined on physical switches using the duplex of a port. 33 00:02:36,280 --> 00:02:37,240 A port. 34 00:02:37,270 --> 00:02:40,480 Operating in full duplex is assumed to be point to point. 35 00:02:40,510 --> 00:02:45,610 Half duplex is considered to be a shared port on switch to in this topology. 36 00:02:45,880 --> 00:02:46,900 Gigabit is zero. 37 00:02:46,900 --> 00:02:54,040 Zero is a point to point link gigabit zero one is a shared port because it's connected to a hub. 38 00:02:54,340 --> 00:02:56,350 It's a half duplex connection. 39 00:02:56,830 --> 00:03:02,440 In today's networks, most links are operating in full duplex mode and are therefore treated as point 40 00:03:02,440 --> 00:03:05,980 to point links between switches in rapid spanning tree.