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Configuring a Root Switch
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. Root guard 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:
Task
Step 1
Enable root guard on a port.
Step 2
Verify that root guard is enabled.
This example shows how to enable root guard:
Console> (enable) set spantree guard root 5/1
Rootguard on port 5/1 is enabled.
Warning!! Enabling rootguard may result in a topolopy change.
Console> (enable)
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 when you enter the clear spantree statistics bpdu command
or when the system is booted.
To display the spanning-tree BPDU statistics, perform this task in normal mode (clear the statistics from
privileged mode):
Task
Step 1
Display spanning-tree BPDU statistics.
Step 2
Clear the BPDU statistics.
Catalyst 6500 Series Switch Software Configuration Guide—Release 8.7
7-48
Command
set spantree guard {root | none} mod/port
show spantree guard {mod/port | vlan} {mistp-instance
instance | mod/port}
Command
show spantree statistics bpdu
clear spantree statistics bpdu
Chapter 7
Configuring Spanning Tree
OL-8978-04
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