Spanning Tree
35
The following fields configure global STP settings:
Table 13. Spanning Tree Bridge Configuration Fields
Field
Description
Spanning Tree Bridge Configuration
Spanning Tree
Click
Enabled
to enable the Spanning Tree protocol mode on all ports. This feature is
disabled on all ports by default.
Protocol Version
Select the protocol version to use:
STP (802.1D). This is the default selection.
RSTP (802.1w)
Max Age
The maximum number of seconds after which BPDU information is considered to be aged out
or invalid. An expired Max Age parameter is typically the result of a link failure.
This value must be less than or equal to 2 x (bridge forward delay – 1) and greater than or
equal to 2 x (bridge hello time + 1).
The range is from 6 to 40 seconds and the default is 20 seconds.
Hello Time
The interval between periodic transmissions of STP BPDUs by designated ports. This value
is set to 2 seconds and cannot be changed.
Forward Delay
The amount of time a bridge remains in a listening and learning state before forwarding
packets. The range is from 4 to 30 seconds and the default is 15 seconds.
Bridge Priority
A value that helps determine which bridge in the spanning tree is elected as the root bridge
during STP convergence. A lower value increases the probability that the bridge becomes the
root bridge. The default value is 32768.
BPDU Guard
When enabled globally, the switch can disable edge ports that receive BPDU packets. This
prevents a new device from entering the existing STP topology. Thus, devices that were
originally not a part of STP are not allowed to influence the STP topology. When disabled, an
edge port that receives a BDPU becomes a non-edge port, which can affect the STP topology.
When enabling BPDU Guard, also ensure that the desired interfaces are operating as edge
ports by enabling the Admin Edge Port mode for each of those interfaces.
This feature is disabled by default.
BPDU Filter
When enabled, this feature filters the BPDU traffic on edge ports. When spanning tree is
disabled on a port, BPDU filtering allows BPDU packets received on that port to be dropped.
When enabling BPDU Filter, also ensure that the desired interfaces are operating as edge
ports by enabling the Admin Edge Port mode for each of those interfaces.
This feature is disabled by default.
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 Bridge Identifier
The bridge ID of the root bridge for the spanning tree. The identifier is made up of the bridge
priority and the base MAC address. When electing the root bridge for the spanning tree, if the
bridge priorities for multiple bridges are equal, the bridge with the lowest MAC address is
elected as the root bridge.
Root Guarded Interfaces
A list of the interfaces for which Root Guard is enabled.
TCN Guarded Interfaces
A list of the interfaces for which TCN Guard is enabled.
BPDU Flood Enabled
Interfaces
A list of the interfaces for which the BPDU Flood feature is enabled.
BPDU Filtered Interfaces
A list of the interfaces for which BPDU Filter is enabled.
