Reference Guide

654 | Multiple Spanning Tree Protocol
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Flush MAC Addresses after a Topology Change
FTOS has an optimized MAC address flush mechanism for RSTP, MSTP, and PVST+ that flushes
addresses only when necessary, which allows for faster convergence during topology changes. However,
you may activate the flushing mechanism defined by 802.1Q-2003 using the command
tc-flush-standard,
which flushes MAC addresses upon every topology change notification. View the enable status of this
feature using the command
show running-config spanning-tree mstp from EXEC Privilege mode.
Displaying STP Guard Configuration
To verify the STP guard configured on MSTP interfaces, enter the show spanning-tree msti
[instance-number] guard
command. Refer to Chapter 52, Spanning Tree Protocol for information on how to
configure and use the STP root guard, loop guard, and BPDU guard features.
Figure 29-9 shows an example for instance 5 in an MSTP network in which:
• Root guard is enabled on a port that is in a root-inconsistent state.
• Loop guard is enabled on a port that is in a forwarding state.
• BPDU guard is enabled on a port that is shut down.
Figure 29-9. Displaying STP Guard Configuration
FTOS#show spanning-tree msti 5 guard
Interface
Name Instance Sts Guard type
--------- -------- --------- ----------
Gi 0/1 5 INCON(Root) Root
Gi 0/2 5 FWD Loop
Gi 0/3 5 EDS(shut) Bpdu