Spanning Tree
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The following fields show global and per-interface STP settings:
Table 12. Spanning Tree Status Fields
Field
Description
Spanning Tree Bridge Status
Spanning Tree
Identifies whether STP is enabled or disabled on the switch.
Protocol Version
Select the protocol version in use:
STP (802.1D). This is the default selection.
RSTP (802.1w)
Switch MAC Address
The MAC address of the switch.
Switch Priority
The configured Spanning Tree priority of this switch. This value that helps determine which
switch in the spanning tree is elected as the root bridge during STP convergence. A lower
value increases the probability that the switch becomes the root bridge. The default value is
32768.
Max Age
The amount of time a bridge waits before implementing a topological change.
Forward Delay
The amount of time a bridge remains in a listening and learning state before forwarding
packets.
Root MAC Address
The MAC address of current root bridge
Root Priority
The Spanning Tree Priority of current root bridge.
Root Path Cost
The sum of the port path costs on the least cost path to the root bridge. For the root bridge
this is zero.
Root Port
The port on the switch that forwards traffic toward the Spanning Tree root.
Topology Change Count
The total number of topology changes since STP was enabled.
Time Since Last Change
Amount of time since the last topology change was detected. The format is DD HH:MM:SS,
representing the time in Days, Hours, Minutes and Seconds.
Spanning Tree Interface Status—The following fields list the interfaces on which the feature is enabled. See
Table 14 on page 37
for descriptions of these features.
Root Guarded Interfaces
A list of interfaces currently having the Root Guard parameter set.
TCN Guarded Interfaces
A list of interfaces currently having the TCN Guard parameter set.
BPDU Protected Interfaces
A list of interfaces currently having the BPDU Guard parameter set.
BPDU Filtered Interfaces
A list of interfaces currently having the BPDU Filter parameter set.
Spanning Tree Interface Status Table
Interface
The port or trunk associated with the rest of the data in the row.
Interface ID
The priority and port index used by the Spanning Tree protocol.
Role
The role of the port with respect to spanning tree functionality, which is one of the following:
Root: A port on the non-root bridge that has the least-cost path to the root bridge.
Designated: A port that has the least-cost path to the root bridge on its segment.
Alternate: A blocked port that has an alternate path to the root bridge.
Backup: A blocked port that has a redundant path to the same network segment as
another port on the bridge.
Disabled: The port is administratively disabled and is not part of the spanning tree.
