BROCADE IP PRIMER

49FLinkPower49FLinkPower50F50FConsole1 3 5 7 9 1113 15 17 19 21 2325 27 29 31 33 3537 39 41 43 45 471F 2F 3F 4F2 4 6 8 10 1214 16 18 20 22 2426 28 30 32 34 3638 40 42 44 46 48Console1 3 5 7 9 1113 15 17 19 21 2325 27 29 31 33 3537 39 41 43 45 471F 2F 3F 4F2 4 6 8 10 1214 16 18 20 22 2426 28 30 32 34 3638 40 42 44 46 4849FLinkPower49FLinkPower50F50FConsole1 3 5 7 9 1113 15 17 19 21 2325 27 29 31 33 3537 39 41 43 45 471F 2F 3F 4F2 4 6 8 10 1214 16 18 20 22 2426 28 30 32 34 3638 40 42 44 46 48Console1 3 5 7 9 1113 15 17 19 21 2325 27 29 31 33 3537 39 41 43 45 471F 2F 3F 4F2 4 6 8 10 1214 16 18 20 22 2426 28 30 32 34 3638 40 42 44 46 48Console49F Link 50F1 3 5 7 9 1113 15 17 19 21 2325 27 29 31 33 3537 39 41 43 45 47Power1F 2F 3F 4F2 4 6 8 10 1214 16 18 20 22 2426 28 30 32 34 3638 40 42 44 46 4849FLinkPower50FConsole1 3 5 7 9 1113 15 17 19 21 2325 27 29 31 33 3537 39 41 43 45 471F 2F 3F 4F2 4 6 8 10 1214 16 18 20 22 2426 28 30 32 34 3638 40 42 44 46 4849FLinkPower50FConsole1 3 5 7 9 1113 15 17 19 21 2325 27 29 31 33 3537 39 41 43 45 471F 2F 3F 4F2 4 6 8 10 1214 16 18 20 22 2426 28 30 32 34 3638 40 42 44 46 48Console49F Link 50F1 3 5 7 9 1113 15 17 19 21 2325 27 29 31 33 3537 39 41 43 45 47Power1F 2F 3F 4F2 4 6 8 10 1214 16 18 20 22 2426 28 30 32 34 3638 40 42 44 46 4849FLinkPower50FConsole1 3 5 7 9 1113 15 17 19 21 2325 27 29 31 33 3537 39 41 43 45 471F 2F 3F 4F2 4 6 8 10 1214 16 18 20 22 2426 28 30 32 34 3638 40 42 44 46 4849FLinkPower50FConsole1 3 5 7 9 1113 15 17 19 21 2325 27 29 31 33 3537 39 41 43 45 471F 2F 3F 4F2 4 6 8 10 1214 16 18 20 22 2426 28 30 32 34 3638 40 42 44 46 4849FLinkPower49FLinkPower50F50FConsole1 3 5 7 9 1113 15 17 19 21 2325 27 29 31 33 3537 39 41 43 45 471F 2F 3F 4F2 4 6 8 10 1214 16 18 20 22 2426 28 30 32 34 3638 40 42 44 46 48Console1 3 5 7 9 1113 15 17 19 21 2325 27 29 31 33 3537 39 41 43 45 471F 2F 3F 4F2 4 6 8 10 1214 16 18 20 22 2426 28 30 32 34 3638 40 42 44 46 4849FLinkPower49FLinkPower50F50FConsole1 3 5 7 9 1113 15 17 19 21 2325 27 29 31 33 3537 39 41 43 45 471F 2F 3F 4F2 4 6 8 10 1214 16 18 20 22 2426 28 30 32 34 3638 40 42 44 46 48Console1 3 5 7 9 1113 15 17 19 21 2325 27 29 31 33 3537 39 41 43 45 471F 2F 3F 4F2 4 6 8 10 1214 16 18 20 22 2426 28 30 32 34 3638 40 42 44 46 48Chapter 9: Spanning Tree ProtocolSometimes, it's not always best to leave the results up to the election, is it?You don't see it? Let's show you the path that Host B will take to talk to Host A:Switch 2MAC: 12:34:56:00:00:02Switch 1MAC: 12:34:36:00:00:01Root switchXSwitch 3MAC: 12:34:56:00:00:03Switch 4MAC: 12:34:56:00:00:04XSwitch 5MAC: 12:34:56:00:00:05XSwitch 6MAC: 12:34:56:00:00:06Host ASwitch 7MAC: 12:34:56:00:00:07It looks as if Host B was flying from Los Angeles to Las Vegas via the PacificOcean, doesn't it? It went through all seven switches! Yet, all it should haveneeded to do was go from Switch 7 directly to Switch 5, and finally to Host A.How can we fix this?As we talked about earlier, the bridge priority, by default, is 32,768. This canbe changed. Let's say we want Switch 4 to be the root switch. We can makesure Switch 4 will win the election by configuring its priority to a lower number,say, 1.Switch4#conf tSwitch4(config)#spanning-tree priority 1If an election has already taken place, issuing this command will force animmediate re-election. Now, Switch 4 becomes the root switch. What effect willthat have on Host A and Host B?Host BSwitch 2MAC: 12:34:56:00:00:02Switch 1MAC: 12:34:36:00:00:01XXXSwitch 3MAC: 12:34:56:00:00:03Switch 5MAC: 12:34:56:00:00:05Switch 4MAC: 12:34:56:00:00:04Priority 1Root SwitchXSwitch 6MAC: 12:34:56:00:00:06Host ASwitch 7MAC: 12:34:56:00:00:07Host B198 Brocade IP Primer