Cisco WS-C4003 Software Guide - Page 127
Using Root Guard—Preventing Switches from Becoming Root, Configuring Spanning Tree Timers
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Chapter 7 Configuring Spanning Tree Configuring Spanning Tree Timers Step 4 Step 5 Step 6 Task Verify the configuration. Configure the maximum aging time for a VLAN or MISTP instance. Verify the configuration. Command show spantree [mod/port] mistp-instance [instances] [active] set spantree maxage agingtime [vlans] mistp-instance instances show spantree [mod/port] mistp-instance [instances] [active] This example shows how to configure the spanning tree Hello Time, Forward Delay Timer, and Maximum Age Timer to 2, 4, and 6 seconds, respectively: Console> (enable) set spantree hello 2 100 Spantree 100 hello time set to 7 seconds. Console> (enable) Console> (enable) set spantree fwddelay 4 100 Spantree 100 forward delay set to 21 seconds. Console> (enable) Console> (enable) set spantree maxage 6 100 Spantree 100 max aging time set to 36 seconds. Console> (enable) 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 will automatically go 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} Configuring Spanning Tree Timers Spanning tree timers affect the spanning tree performance. You can configure the spanning tree timers for a VLAN in PVST+ or a MISTP instance in MISTP mode. If you do not specify a VLAN when the switch is in PVST+ mode, VLAN 1 is assumed, oif you do not specify a MISTP instance when the switch is in MISTP mode, MISTP instance 1 is assumed. 78-12647-02 Software Configuration Guide-Catalyst 4000 Family, Catalyst 2948G, Catalyst 2980G, Releases 6.3 and 6.4 7-31