Cisco WS-C2960-48TT-S-RF Software Guide - Page 139
Using Root Guard—Preventing Switches from Becoming Root, Displaying Spanning Tree BPDU Statistics
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Chapter 7 Configuring Spanning Tree Configuring a Root Switch Console> (enable) set spantree root 1-10 dia 4 VLANs 1-10 bridge priority set to 8192 VLANs 1-10 bridge max aging time set to 14 seconds. VLANs 1-10 bridge hello time set to 2 seconds. VLANs 1-10 bridge forward delay set to 9 seconds. Switch is now the root switch for active VLANs 1-6. Console> (enable) Using Root Guard-Preventing Switches from Becoming Root You may want to prevent switches from becoming the root switch. The root guard feature forces a port to become a designated port so that no switch on the other end of the link can become a root switch. When you enable root guard on a per-port basis, it is automatically applied to all of the active VLANs to which that port belongs. When you disable root guard, it is disabled for the specified port(s). If a port goes into the root-inconsistent state, it automatically goes into the listening state. To prevent switches from becoming root, perform this task in privileged mode: Step 1 Step 2 Task Enable root guard on a port. Verify that root guard is enabled. Command set spantree guard {root | none} mod/port show spantree guard {mod/port | vlan} {mistp-instance instance | mod/port} Displaying Spanning Tree BPDU Statistics Enter the show spantree statistics bpdu command to display the total number of spanning tree BPDUs (transmitted, received, processed, and dropped). The command also provides the rate of the BPDUs in seconds. The BPDU counters are cleared using the clear spantree statistics bpdu command or when the system is booted. To display spanning tree BPDU statistics, perform this task in normal mode (clear the statistics from privileged mode): Step 1 Step 2 Task Display spanning tree BPDU statistics. Clear the BPDU statistics. Command show spantree statistics bpdu clear spantree statistics bpdu This example shows how to display spanning tree BPDU statistics: Console> show spantree statistics bpdu Transmitted Received Processed Dropped Total 52943073 52016589 52016422 167 Rate(/sec) 989 971 971 0 This example shows how to clear spanning tree BPDU statistics: Console> (enable) clear spantree statistics bpdu Spanning tree BPDU statistics cleared on the switch. Console> (enable) 78-15486-01 Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 7-43
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