3.9. MSTP Commands

Command Purpose

Use this command to enable the Spanning Tree Protocol on a bridge. Use the no parameter to disable the Spanning Tree Protocol on the bridge.

Prerequisites

Command Syntax

spanning-tree enable

no spanning-tree enable

Command Mode

Global Config

Default

Disable

Usage

None

Examples

This example shows how to global enable stp:

Switch# configure terminal
Switch(config)# spanning-tree enable

This example shows how to global disable stp:

Switch# configure terminal
Switch(config)# no spanning-tree enable

Related Commands

show spanning-stree

Command Purpose

Use this command to set the bridge priority for the common instance for the default bridge. Using a lower priority indicates a higher likelihood of the bridge becoming root. Use the no parameter with this command to reset it to the default value.

Prerequisites

Command Syntax

spanning-tree priority PRIORITY

no spanning-tree priority

Command Mode

Global Config

Default

The default priority is 32678 (or hex 0x8000)

Usage

This command is used to set the priority of the bridge. The priority values must be in multiples of 4096.

Examples

This example shows how to set the bridge priority.:

Switch# configure terminal
Switch(config)# spanning-tree priority 4096

This example shows how to reset the bridge priority to default value:

Switch# configure terminal
Switch(config)# no spanning-tree priority

Related Commands

show spanning-stree

Command Purpose

Use this command to set the default bridge priority for an MST instance to the value specified. Use the no parameter with this command to restore the default value of the default bridge priority.

Prerequisites

Command Syntax

spanning-tree instance INSTANCE_ID priority PRIORITY

no spanning-tree instance INSTANCE_ID priority

Command Mode

Global Config

Default

The default value of port priority for each instance is 32768.

Usage

The lower the priority of the bridge, there is higher likelihood that the bridge becomes a root bridge or a designated bridge for the LAN. The permitted range of values is 0-61440. The priority values must be in multiples of 4096.

Examples

This example shows how to set the priority for instance 1:

Switch# configure terminal
Switch(config)# spanning-tree instance 1 priority 0

Related Commands

show spanning-stree

Command Purpose

Use this command to set the time after which (if this bridge is the root bridge) each port in the default bridge changes states to learning and forwarding. This value is used by all instances. Use the no parameter with this command to restore the default value of 15 seconds.

Prerequisites

Command Syntax

spanning-tree forward-time SECONDS

no spanning-tree forward-time

Command Mode

Global Config

Default

The default value is 15 seconds

Usage

The allowable range for the forward time is 4-30 seconds. It is not advisable to set the value below 7 seconds.

Examples

This example shows how to set the forward time to 16 seconds:

Switch# configure terminal
Switch(config)# spanning-tree forward-time 16

This example shows how to reset the forward time to default value:

Switch# configure terminal
Switch(config)# no spanning-tree forward-time

Related Commands

show spanning-stree

Command Purpose

Use this command to set the hello-time, the time in seconds after which (if this bridge is the root bridge) all the default bridges in a bridged LAN exchange Bridge Protocol Data Units (BPDUs). A very low value of this parameter leads to excessive traffic on the network, while a higher value delays the detection of topology change. This value is used by all instances.

Prerequisites

Command Syntax

spanning-tree hello-time SECONDS

no spanning-tree hello-time

Command Mode

Global Config

Default

The default hello-time value is 2

Usage

The allowable range of values is 1-10 seconds.

Examples

This example shows how to set the hello time to 5 seconds:

Switch# configure terminal
Switch(config)# spanning-tree hello-time 5

This example shows how to reset the hello-time to default value:

Switch# configure terminal
Switch(config)# no spanning-tree hello-time

Related Commands

show spanning-stree

Command Purpose

Use this command to set the maximum age for the default bridge. Use the no parameter with this command to restore the default value of the maximum age.

Prerequisites

Command Syntax

spanning-tree max-age SECONDS

no spanning-tree max-age

Command Mode

Global Config

Default

The default value of bridge maximum age is 20 seconds.

Usage

Maximum age is the maximum time for which (if a bridge is the root bridge) a message is considered valid. This prevents the frames from looping indefinitely. The value of maximum age should be greater than twice the value of hello time plus 1, and less than twice the value of forward delay minus 1. The allowable range for maximum age is 6-40 seconds. Configure this value sufficiently high, so that a frame generated by root can be propagated to the leaf nodes without exceeding the maximum age.

Examples

This example shows how to set the max age to 12 seconds:

Switch# configure terminal
Switch(config)# spanning-tree max-age 12

This example shows how to reset the max age to default value:

Switch# configure terminal
Switch(config)# no spanning-tree max-age

Related Commands

show spanning-tree

Command Purpose

Use this command to specify the maximum allowed hops for a BPDU in an MST region. This parameter is used by all the instances of the MST. To restore the default value, use the no parameter with this command.

Prerequisites

Command Syntax

spanning-tree max-hops NUMBER

no spanning-tree max-hops

Command Mode

Global Config

Default

The default maximum hops in an MST region are 20

Usage

Specifying the maximum hops for a BPDU prevents the messages from looping indefinitely in the network. When a bridge receives an MST BPDU that has exceeded the allowed maximum hops, it discards the BPDU packets.

The configuration should be shown when the bridge is MSTP mode.

Examples

This example shows how to set the max hops to 25:

Switch# configure terminal
Switch(config)# spanning-tree max-hops 25

This example shows how to reset the max hops to default value:

Switch# configure terminal
Switch(config)# no spanning-tree max-hops

Related Commands

show spanning-tree

Command Purpose

Use this command to set the maximum number of transmissions of BPDUs in an MST region by the transmit state machine. Use the no parameter with this command to restore the default transmit hold-count value.

Prerequisites

Command Syntax

spanning-tree transmit-holdcount NUMBER

no spanning-tree transmit-holdcount

Command Mode

Global Config

Default

Transmit hold-count default value is 3

Usage

None

Examples

This example shows how to set hold count to 5:

Switch# configure terminal
Switch(config)# spanning-tree transmit-holdcount 5

This example shows how to reset the hold count to default value:

Switch# configure terminal
Switch(config)# no spanning-tree transmit-holdcount

Related Commands

show spanning-tree

Command Purpose

Use this command to enable the BPDU (Bridge Protocol Data Unit) Guard feature on a bridge globally.

Use the no parameter with this command to disable the BPDU Guard feature on a bridge globally.

Prerequisites

Command Syntax

spanning-tree edgeport bpdu-guard

no spanning-tree edgeport bpdu-guard

Command Mode

Global Config

Default

BPDU guard is disabled

Usage

Use the show spanning-tree command to display the bridge and port configurations for the BPDU Guard feature. It shows both the administratively configured and currently running values of the BPDU guard.

Examples

This example shows how to enable bpdu-guard globally:

Switch# configure terminal
Switch(config)# spanning-tree edgeport bpdu-guard

Related Commands

show spanning-tree

Command Purpose

Use this command to enable the edgeport BPDU filter for the bridge globally.

Use the no parameter with this command to disable the BPDU filter for the bridge globally.

Prerequisites

Command Syntax

spanning-tree edgeport bpdu-filter

no spanning-tree edgeport bpdu-filter

Command Mode

Global Config

Default

BPDU filter is disabled

Usage

Use the show spanning tree command to display administratively configured and currently running values of the BPDU filter parameter for the bridge and port.

If bpdu-guard and bpdu-filter are all configed on port, bpdu-filter has a higher priority.

Examples

This example shows how to enable bpdu-filter globally:

Switch# configure terminal
Switch(config)# spanning-tree edgeport bpdu-filter

Related Commands

show spanning-tree

Command Purpose

Use this command to enable or disable spanning tree protocol on specified port.

Prerequisites

Command Syntax

spanning-tree port ( enable | disable )

Command Mode

Interface Configuration

Default

The default spanning tree state of the port is enabled.

Usage

None

Examples

This example shows how to enable STP on port eth-0-1:

Switch# configure terminal
Switch(config)# interface eth-0-1
Switch(config-if)# spanning-tree port enable

This example shows how to disable STP on port eth-0-1:

Switch# configure terminal
Switch(config-if)# spanning-tree port disable

Related Commands

show spanning-tree interface

Command Purpose

Use this command to set the port priority for a bridge. A lower priority indicates a greater likelihood of the bridge becoming root.

Prerequisites

Command Syntax

spanning-tree port-priority PRIORITY

no spanning-tree port-priority

Command Mode

Interface Configuration

Default

The default priority is 128

Usage

None

Examples

This example shows how to set the priority to 240 on port eth-0-1:

Switch# configure terminal
Switch(config)# interface eth-0-1
Switch(config-if)# spanning-tree port-priority 240

Related Commands

show spanning-tree interface

Command Purpose

Use this command to set the path cost standard associated with the default bridge-group. Use the no parameter with this command to set to default value.

Prerequisites

Command Syntax

spanning-tree pathcost-standard ( dot1d-1998 | dot1t )

no spanning-tree pathcost-standard

Command Mode

Global Config

Default

The default pathcost-standard is dot1t

Usage

If the pathcost-standard is changed, cost of every port will be reset and auto-calculated.

Examples

This example shows how to set the path cost standard:

Switch# configure terminal
Switch(config)# spanning-tree pathcost-standard dot1d-1998

Cost of every port has been reset and auto-calculation is available

Related Commands

show spanning-tree

Command Purpose

Use this command to set the cost of a path associated with the default bridge-group. The lower the path cost, the greater likelihood of the bridge becoming root. Use the no parameter with this command to calculate path cost according to interface’s speed.

Prerequisites

Command Syntax

spanning-tree path-cost NUMBER

no spanning-tree path-cost

Command Mode

Interface Configuration

Default

The default path cost value is calculated according to interface’s speed

Usage

None

Examples

This example shows how to set the STP path-cost to 123:

Switch# configure terminal
Switch(config)# interface eth-0-1
Switch(config-if)# spanning-tree path-cost 123

This example shows how to reset the STP path-cost to deafult value:

Switch# configure terminal
Switch(config-if)# no spanning-tree path-cost

Related Commands

show spanning-tree interface

Command Purpose

Use this command to enable or disable point-to-point or shared link types. Use the no parameter with this command to disable rapid transition.

Prerequisites

Command Syntax

spanning-tree link-type ( auto | point-to-point | shared )

no spanning-tree link-type

Command Mode

Interface Configuration

Default

The link type is auto detected

Usage

None

Examples

This example shows how to set the link type to shared on port eth-0-1:

Switch# configure terminal
Switch(config)# interface eth-0-1
Switch(config-if)# spanning-tree link-type shared

Related Commands

show spanning-tree brief

Command Purpose

Use this command to set a port as an edge-port and to enable rapid transitions. Use the no parameter with this command to set a port to its default state (not an edge-port) and to disable rapid transitions.

Prerequisites

Command Syntax

spanning-tree edgeport

no spanning-tree edgeport

Command Mode

Interface Configuration

Default

The port is not an edge-port

Usage

None

Examples

This example shows how to set the port eth-0-1 to edgeport:

Switch# configure terminal
Switch(config)# interface eth-0-1
Switch(config-if)# spanning-tree edgeport

This example shows how to reset the port to an non-edgeport:

Switch# configure terminal
Switch(config-if)# no spanning-tree edgeport

Related Commands

show spanning-tree interface

Command Purpose

Use this command to enable or disable the BPDU Guard feature on a port. Use the no parameter with this command to set the BPDU Guard feature on a port to default.

Prerequisites

Command Syntax

spanning-tree edgeport bpdu-guard ( enable | disable | default )

no spanning-tree edgeport bpdu-guard

Command Mode

Interface Configuration

Default

BPDU guard is disabled on port

Usage

None

Examples

This example shows how to change port to edgeport and enable bpdu-guard on port:

Switch# configure terminal
Switch(config)# interface eth-0-1
Switch(config-if)# spanning-tree edgeport
Switch(config-if)# spanning-tree edgeport bpdu-guard enable

Related Commands

show spanning tree interface

Command Purpose

Use this command to set edgeport BPDU filter for the port. Use the no parameter with this command to revert the port BPDU filter value to default.

Prerequisites

Command Syntax

spanning-tree edgeport bpdu-filter ( enable | disable | default )

no spanning-tree edgeport bpdu-filter

Command Mode

Interface Configuration

Default

BPDU filter is disabled on port

Usage

None

Examples

This example shows how to enable bpdu-filter on port:

Switch# configure terminal
Switch(config)# interface eth-0-1
Switch(config-if)# spanning-tree edgeport
Switch(config-if)# spanning-tree edgeport bpdu-filter

This example shows how to disable bpdu-filter on port:

Switch# configure terminal
Switch(config-if)# no spanning-tree edgeport bpdu-filter

Related Commands

show spanning tree interface

Command Purpose

Use this command to enable the Root Guard feature for the port. This feature disables reception of superior BPDUs. Use the no parameter with this command to disable the root guard feature for the port.

Prerequisites

Command Syntax

spanning-tree guard root

no spanning-tree guard root

Command Mode

Interface Configuration

Default

Root guard is disabled

Usage

The Root Guard feature makes sure that the port on which it is enabled is a designated port. If a port with Root Guard enabled receives a superior BPDU, it goes to a Listening state (for STP) or discarding state (for RSTP and MSTP).

Examples

This example shows how to enable the Root Guard feature for the port:

Switch# configure terminal
Switch(config)# interface eth-0-1
Switch(config-if)# spanning-tree guard root

This example shows how to disable the Root Guard feature for the port:

Switch# configure terminal
Switch(config)# interface eth-0-1
Switch(config-if)# no spanning-tree guard root

Related Commands

None

Command Purpose

Use this command to enable the loop guard feature for the port. This feature provides additional protection against Layer 2 forwarding loops. Use the no parameter with this command to disable the loop guard feature for the port.

Prerequisites

Command Syntax

spanning-tree guard loop

no spanning-tree guard loop

Command Mode

Interface Configuration

Default

Loop guard is disabled

Usage

The loop guard feature should be enabled on the non-designated ports. When a port enables loop guard, and BPDUs are not received on a non-designated port after max_age, the port should move into the STP loop-inconsistent blocking state, instead of the listening / learning / forwarding state, and should not pass user traffic.

Examples

This example shows how to enable the loop guard on the port:

Switch# configure terminal
Switch(config)# interface eth-0-1
Switch(config-if)# spanning-tree guard loop

This example shows how to disable the loop guard on the port:

Switch# configure terminal
Switch(config)# interface eth-0-1
Switch(config-if)# no spanning-tree guard loop

Related Commands

spanning-tree guard root

Command Purpose

Use this command to enable the bpdu loop feature for the port. This feature provides additional protection against BPDU packet forwarding loops. Use the no parameter with this command to disable the loop guard feature for the port.

Prerequisites

Command Syntax

spanning-tree bpdu-loop

no spanning-tree bpdu-loop

Command Mode

Global Config

Default

BPDU loop is enabled

Usage

When bpdu-loop enable, If an interface receives more than three bpdu packets in one second whose MACSA is interface’s MAC, errdisable this interface by bpdu loop reason.

Examples

This example shows how to enable the bpdu-loop:

Switch# configure terminal
Switch(config)# spanning-tree bpdu-loop

This example shows how to disable the bpdu-loop:

Switch# configure terminal
Switch(config)# no spanning-tree bpdu-loop

Related Commands

None

Command Purpose

Use this command to specify the version. A version identifier of less than a value of 2 enforces the spanning tree protocol. Although the command supports an input range of 0-3, for RSTP, the valid range is 0-2. Use the no parameter with this command to set the default protocol version.

Prerequisites

Command Syntax

spanning-tree force-version NUMBER

no spanning-tree force-version

Command Mode

Interface Configuration

Default

STP default 0, RSTP default 2, MSTP default 3

Usage

None

Examples

This example shows how to specify the version:

Switch# configure terminal
Switch(config)# interface eth-0-1
Switch(config-if)# spanning-tree force-version 1

This example shows how to reset the default version:

Switch# configure terminal
Switch(config)# interface eth-0-1
Switch(config-if)# no spanning-tree force-version

Related Commands

None

Command Purpose

Use this command to set the restricted TCN value of the port to TRUE. Use the no parameter with this command to set the restricted TCN value of the port to FALSE.

Prerequisites

Command Syntax

spanning-tree restricted-tcn

no spanning-tree restricted-tcn

Command Mode

Interface Configuration

Default

The default restricted TCN value is FALSE

Usage

None

Examples

This example shows how to set the restricted TCN value of the port to TRUE:

Switch# configure terminal
Switch(config)# interface eth-0-1
Switch(config-if)# spanning-tree restricted-tcn

This example shows how to set the restricted TCN value of the port to FALSE:

Switch# configure terminal
Switch(config)# interface eth-0-1
Switch(config-if)# no spanning-tree restricted-tcn

Related Commands

None

Command Purpose

Use this command to set the restricted-role value of the port to TRUE. Use the no parameter with this command to set the restricted-role value of the port to FALSE.

Prerequisites

Command Syntax

spanning-tree restricted-role

no spanning-tree restricted-role

Command Mode

Interface Configuration

Default

The default restricted-role value is FALSE

Usage

None

Examples

This example shows how to set the restricted-role value of the port to TRUE:

Switch# configure terminal
Switch(config)# interface eth-0-1
Switch(config-if)# spanning-tree restricted-role

This example shows how to set the restricted-role value of the port to FALSE:

Switch# configure terminal
Switch(config)# interface eth-0-1
Switch(config-if)# no spanning-tree restricted-role

Related Commands

None

Command Purpose

Use this command to set the tc-protection value to TRUE. Use the no parameter with this command to set the tc-protection value to FALSE. If tc-protection is set, the number of tc packets which can be processed every hello time interval shouldn’t be greater than the number of tc-protection threshold.

Prerequisites

Command Syntax

spanning-tree tc-protection

no spanning-tree tc-protection

Command Mode

Global Config

Default

The default tc-protection value is FALSE

Usage

None

Examples

This example shows how to set the tc-protection value to TRUE:

Switch# configure terminal
Switch(config)# spanning-tree tc-protection

This example shows how to set the tc-protection value to FALSE:

Switch# configure terminal
Switch(config)# no spanning-tree tc-protection

Related Commands

None

Command Purpose

Use this command to set the tc-protection threshold value. Use the no parameter with this command to set the tc-protection threshold value to 1. If tc-protection is set, the number of tc packets which can be processed every hello time interval shouldn’t be greater than the number of tc-protection threshold.

Prerequisites

Command Syntax

spanning-tree tc-protection threshold NUMBER

no spanning-tree tc-protection threshold