Specifies that spanning tree will run in MSTP mode.

Clears spanning tree debug counters.

Resets the configuration name of the MST region in which the switch resides. This name can include up to 32 nonblank characters and is case-sensitive. On all switches within a given MST region, the configuration names must be identical. For more than one MSTP switch in the same MST region, the identical region name must be configured on all such switches. If the default configuration name is retained on a switch, it cannot exist in the same MST region with another switch.

The default name is a text string using the hexadecimal representation of the switch's MAC address.

The no form of the command overwrites the currently configured name with the default name.

	NOTE: This option is available only when the switch is configured for MSTP operation. There is no defined limit on the number of regions you can configure.

Configures the revision number designated for the MST region in which you want the switch to reside. This setting must be the same for all switches residing in the same region. Use this setting to differentiate between region configurations in situations such as the following:

• Changing configuration settings within a region where you want to track the configuration versions you use

• Creating a new region from a subset of switches in a current region and want to maintain the same region name.

• Using the pending option to maintain two different configuration options for the same physical region.

This setting must be the same for all MSTP switches in the same MST region.

Range: 0 - 65535

Default: 0

	NOTE: This option is available only when the switch is configured for MSTP operation.

Sets the spanning tree compatibility mode. This command forces the switch to emulate behavior of earlier versions of spanning tree protocol, or return to MSTP behavior. The command is useful in test or debug applications, and removes the need to reconfigure the switch for temporary changes in spanning tree operation.

stp-compatible	The switch applies 802.1D STP operation on all ports.
rstp-operation	The switch applies 802.1w operation on all ports except those ports where it detects a system using 802.1D Spanning Tree. RSTP is Rapid Spanning Tree Protocol.
mstp-operation	The switch applies 802.1s MSTP operation on all ports where compatibility with 802.1D or 802.1w spanning tree protocols is not required.

	NOTE: Even when mstp-operation is selected, if the switch detects an 802.1D BPDU or an 802.1w BPDU on a port, it communicates with the device linked to that port using STP or RSTP BPDU packets. Also, if errors are encountered as described in Configuring MSTP at a glance, setting force-version to stp-compatible forces the MSTP switch to communicate out all ports using operations that are compatible with IEEE 802.1D STP.

	NOTE: When using MSTP rapid state transitions Under some circumstances the rapid state transitions employed by MSTP can increase the rates of frame duplication and incorrect ordering in the switched LAN. To allow MSTP switches to support applications and protocols that may be sensitive to frame duplication and incorrect ordering, setting the Force Protocol Version (force-version) parameter to stp-compatible allows MSTP to operate with rapid transitions disabled. The value of this parameter applies to all ports on the switch.

Sets the time the switch waits between transitions from listening to learning and from learning to forwarding states.

Range: 4 - 30

Default: 15 seconds

Forces spanning tree to operate in legacy (802.!D) mode.

Default: MSTP-operation.

The no form of this command returns the switch to the default 802.1s native mode (MSTP-operation.)

Forces spanning tree to operate with legacy (802.!D) path cost values.

Default: 802.1t.

The no form of the command returns the switch to the default 802.1t (not legacy) path cost values.

If MSTP is running and the switch is operating as the CIST (Common and Internal Spanning Tree) root for your network, this command specifies the time in seconds between transmissions of BPDUs for all ports on the switch configured with the Global option (the default). This parameter applies in MSTP, RSTP and STP modes.

During MSTP operation, you can override this global setting on a per-port basis with this command: spanning-tree port-list hello-time 1..10 .

Default: 2 seconds.

Resets the number of hops allowed for BPDUs in an MST region. When an MSTP switch receives a BPDU, it decrements the hop-count setting the BPDU carries. If the hop-count reaches zero, the receiving switch drops the BPDU.

Note that the switch does not change the message-age and maximum-age data carried in the BPDU as it moves through the MST region and is propagated to other regions.

Range: 1 - 40

Default: 20

Sets the maximum age time for received STP information before it is discarded.

Default: 20 seconds

Manipulates the pending MSTP configuration. The command is useful in test or debug applications, and enables rapid reconfiguration of the switch for changes in spanning tree operation.

apply	Applies pending MSTP configuration (swaps active and pending configurations).
config-name	Sets the pending MST region configuration name. Default is the switch's MAC address.
config-revision	Sets the pending MST region configuration revision number. Default is 0.
instance	Change pending MST instance configuration.
reset	Copies the active configuration to pending.

Every switch running an instance of MSTP has a Bridge Identifier, which is a unique identifier that helps distinguish this switch from all others. The switch with the lowest Bridge Identifier is elected as the root for the tree.

The Bridge Identifier is composed of a configurable priority component (2 bytes) and the bridge's MAC address (6 bytes). You can change the priority component provides flexibility in determining which switch will be the root for the tree, regardless of its MAC address.

This command sets the switch (bridge) priority for the designated region in which the switch resides. The switch compares this priority with the priorities of other switches in the same region to determine the root switch for the region. The lower the priority value, the higher the priority. If there is only one switch in the region, then that switch is the root switch for the region. The root bridge in a region provides the path to connected regions for the traffic in VLANs assigned to the region's IST instance. Traffic in VLANs assigned to a numbered STP instance in a given region moves to other regions through the root switch for that instance.

The priority range for an MSTP switch is 0-61440. However, this command specifies the priority as a multiplier (0 - 15) of 4096. That is, when you specify a priority multiplier value of 0 - 15, the actual priority assigned to the switch is: (priority-multiplier) x 4096

For example, with 2 as the priority-multiplier on a given MSTP switch, the Switch Priority setting is 8,192.

	NOTE: If multiple switches in the same MST region have the same priority setting, then the switch with the lowest MAC address becomes the root switch for that region.

Enables or disables SNMP traps for errant-BPDU, loop guard, new root, and root guard event notifications. Note that this command is designed to be used in conjunction with the spanning-tree bpdu-filter command and the bpdu-protection command.

errant-bpdu	Enables SNMP notification when an errant BPDU is received. Designed for use with BPDU filtering.
loop-guard	Enables SNMP notification when a loop guard inconsistency is detected. Designed for use with the Loop Guard option.
new-root	Enables SNMP notification when a new root is elected on any VLAN configured for MSTP on the switch.
root-guard	Enables SNMP notification when a root guard inconsistency is detected.

Enables admin-edge-port on ports connected to end nodes. During spanning tree establishment, ports with admin-edge-port enabled transition immediately to the forwarding state. If a bridge or switch is detected on the segment, the port automatically operates as non-edge, not enabled.

Default: Disabled

If admin-edge-port is disabled on a port and auto-edge-port has not been disabled, the auto-edge-port setting controls the behavior of the port.

The no form of this command disables edge port operation on the specified ports.

Enables automatic identification of edge ports for faster convergence. When enabled, the port looks for BPDUs for the first 3 seconds. If there are none, the port is classified as an edge port and immediately starts forwarding packets. If BPDUs are seen on the port, the port is classified as a non‐edge port and normal STP operation commences on that port.

If admin-edge-port is enabled for a port, the setting for auto-edge-port is ignored whether set to yes or no.

If admin-edge-port is set to no, and auto-edge-port has not been disabled (set to no), then the auto-edge-port setting controls the behavior of the port.

	NOTE: See“Caution”. Requires thorough knowledge of IEEE 802.1D/w/s standards and operation.

Default: Enabled

The no form of this command disables auto-edge-port operation on the specified ports.

When the switch is the CIST root, this parameter specifies the interval (in seconds) between periodic BPDU transmissions by the designated ports. This interval also applies to all ports in all switches downstream from each port in the port-list.

A setting of global indicates that the ports in port-list on the CIST root are using the value set by the global spanning tree hello-time value.

When a given switch X is not the CIST root, the per-port hello-time for all active ports on switch X is propagated from the CIST root, and is the same as the hello-time in use on the CIST root port in the currently active path from switch X to the CIST root. When switch X is not the CIST root, then the upstream CIST root's port hello-time setting overrides the hello-time setting configured on switch X.

Default Per-Port setting: Use Global.

Default Global Hello-Time: 2.

Forces a port to send RST/MST BPDUs for 3 seconds. This tests whether all STP bridges on the attached LAN have been removed and the port can migrate to native MSTP mode and use RST/MST BPDUs for transmission.

Assigns an individual port cost that the switch uses to determine which ports are forwarding ports in a given spanning tree. In the default configuration (auto) the switch determines a port's path cost by the port's type:

10 Mbps	2000000
100 Mbps	200000
1 Gbps	20000

Default: Auto

Informs the switch of the type of device to which a specific port connects.

true	(Default) Indicates a point-to-point link to a device such as a switch, bridge, or end-node.
false	Indicates a connection to a half-duplex repeater (which is a shared LAN segment).
auto	Causes the switch to set Force-False on the port if it is not running at full duplex.

MSTP uses this parameter to determine the port to use for forwarding. The port with the lowest priority number has the highest priority for use.

The range is 0 to 240, and is configured by specifying a multiplier from 0 - 15. When you specify a priority multiplier of 0 - 15, the actual priority assigned to the switch is:

(priority-multiplier) x 16

If you configure 2 as the priority multiplier on a given port, the actual Priority setting is 32. After specifying the port priority multiplier, the switch displays the actual port priority (and not the multiplier) in the show spanning-tree or show spanning-tree port-list displays.

You can view the actual multiplier setting for ports by executing show running and looking for an entry in this format:

spanning-treeport-list priority priority-multiplier

For example, configuring port A2 with a priority multiplier of 3 results in the following line in the show running output:

spanning-tree A2 priority 3

When a port is enabled as root-guard, it cannot be selected as the root port even if it receives superior STP BPDUs. The port is assigned an "alternate" port role and enters a blocking state if it receives superior STP BPDUs.

A superior BPDU contains both "better" information on the root bridge and path cost to the root bridge, which would normally replace the current root bridge selection.

The superior BPDUs received on a port enabled as root-guard are ignored. All other BPDUs are accepted and the external devices may belong to the spanning tree as long as they do not claim to be the Root device.

Use this command on MSTP switch ports that are connected to devices located in other administrative network domains to:

• Ensure the stability of the core MSTP network topology so that undesired or damaging influences external to the network do not enter.

• Protect the configuration of the CIST root bridge that serves as the common root for the entire network.

Default: Disabled

When enabled for a port, this causes the port to stop propagating received topology change notifications and topology changes to other ports.

Default: Disabled