Using Root Guard-Preventing Switches From Becoming Root; Displaying Spanning Tree Bpdu Statistics - Cisco WS-C2948G-GE-TX Configuration Manual

Chapter 7 Configuring Spanning Tree
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:
Task
Step 1
Enable root guard on a port.
Step 2
Verify that root guard is enabled.

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):
Task
Step 1
Display spanning tree BPDU statistics.
Step 2 Clear the BPDU statistics.
This example shows how to display spanning tree BPDU statistics:
Console> show spantree statistics bpdu
Total
Rate(/sec)
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)
Catalyst 4500 Series, Catalyst 2948G, Catalyst 2948G-GE-TX, and Catalyst 2980G Switches Software Configuration Guide—Release 8.2GLX
78-15908-01
Transmitted Received
-------------- -------------- -------------- --------------
52943073 52016589
989
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
Processed
52016422
971 971
Configuring a Root Switch
Dropped
167
0
7-43