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Configuring RSTP Protocol

Understanding RSTP

Juniper Networks products use Rapid Spanning Tree Protocol (RSTP) on the network side of devices by default to provide quicker convergence time than the base Spanning Tree Protocol (STP) does. RSTP identifies certain links as point to point. When a point-to-point link fails, the alternate link can transition to the forwarding state, which speeds up convergence.

Benefits of Using RSTP

Some benefits of using the original STP are:

  • RSTP is faster than STP.

  • Voice and video work better with RSTP than they do with STP.

  • RSTP supports more ports than MSTP or VSTP.

  • RSTP is backward compatible with STP; therefore, switches do not all have to run RSTP.

  • On MX and ACX routers, you can configure RSTP, MSTP, and VSTP instance interfaces as edge ports.

Why is RSTP the Default Spanning-Tree Protocol?

RSTP evolved from the original STP IEEE 802.1D protocol to provide faster spanning-tree reconvergence after a switch port, switch, or LAN failure. Where STP took up to 50 seconds to respond to topology changes, RSTP responds to changes within the timeframe of three hello BPDUs (bridge protocol data units), or 6 seconds. This is the primary reason that RSTP is the default spanning-tree configuration.

Tip:

EX Series switches configured to use STP actually run RSTP force version 0, which is compatible with STP.

Configuring Rapid Spanning Tree Protocol

You can configure Rapid Spanning Tree Protocol (RSTP) under the following hierarchy levels:

  • [edit logical-systems logical-system-name protocols]

  • [edit logical-systems logical-system-name routing-instances  routing-instance-name protocols]

  • [edit protocols]

  • [edit routing-instances routing-instance-name protocols]

The routing instance type can be either virtual-switch or layer2-control.

To configure the Rapid Spanning Tree Protocol:

  1. Enable RSTP as the version of spanning-tree protocol to be configured:
  2. (Optional) For compatibility with older bridges that do  not support RSTP, you can force RSTP to run as the original IEEE 802.1D Spanning Tree Protocol (STP) version:
    Note:

    If RSTP has been forced to run as the original STP version, you can revert back to RSTP by first removing the force-version statement from the configuration and then entering the clear spanning-tree protocol-migration configuration mode command.

  3. (Optional) Enable provider bridge participation in the RSTP instance:
  4. (Optional) Specify the extended system identifier used in identifiers bridges that participate in RSTP:
  5. Configure the interfaces that participate in the RSTP instance.
    1. Enable configuration of the interface:
    2. Configure the interface priority:
    3. (Optional) By default, the interface link cost is determined by the link speed. You can configure the interface link cost to control which bridge is the designated bridge and which port is the designated port:
    4. Configure the interface link mode to identify point-to-point links:

      Specify p2p if the link is point to point. Specify shared if the link is a shared media.

    5. (Optional) Configure the interface as an edge port:

      Edge ports do not expect to receive bridge protocol data unit (BPDU) packets. If a BPDU packet is received for an edge port, the port becomes a non-edge port

    You can also enable BPDU root protection for all spanning-tree protocol instances on the interface. BPDU root protect ensures the port is the spanning-tree designated port. If the port receives superior BPDU packets, root protect moves this port to a root-prevented spanning-tree state. For configuration details, see Checking the Status of Spanning-Tree Instance Interfaces.

  6. Configure the bridge priority:
  7. Configure hello BPDU timers.
    1. Configure the maximum expected arrival time of hello BPDUs:
    2. Configure the time interval at which the root bridge transmits configuration BPDUs:
  8. (Optional) By default, the bridge port remains in the listening and learning states for 15  seconds before transitioning to the forwarding state. You can specify a delay from 4 through 20 seconds instead:
  9. Verify the RSTP configuration:

Configuring RSTP on EX Series Switches (CLI Procedure)

The default spanning-tree protocol for EX Series switches is Rapid Spanning Tree Protocol (RSTP). RSTP provides faster convergence times than the original Spanning Tree Protocol (STP). Because RSTP is configured by default, you only need to use this procedure If another spanning-tree protocol has been configured. In that case, you can reconfigure RSTP.

To enable RSTP:

  1. Disable the other configured spanning-tree protocol (MSTP):
    • To disable MSTP:

  2. Configure RSTP
    • To enable RSTP on a specific interface:

    • To disable RSTP on a specific interface:

    • To enable RSTP on a range of interfaces:

    • To enable RSTP on all interfaces:

Example: Configuring Faster Convergence and Network Stability on ELS Switches with RSTP

Note:

This example uses Junos OS for EX Series switches with support for the Enhanced Layer 2 Software (ELS) configuration style. If your switch runs software that does not support ELS, see Example: Faster Convergence and Improved Network Stability with RSTP on EX Series Switches. For ELS details, see Using the Enhanced Layer 2 Software CLI.

EX Series switches use Rapid Spanning Tree Protocol (RSTP) by default to provide a loop-free topology.

When switches that support redundant Routing Engines use RSTP, it is important to keep RSTP synchronized on both Routing Engines so that no loss of service occurs after a Routing Engine switchover. Nonstop bridging protocol keeps Routing Engines synchronized.

This example describes how to configure RSTP and NSB on four EX Series switches:

Requirements

This example uses the following software and hardware components:

  • Junos OS Release 15.1 or later or later for EX Series switches

  • Four EX Series switches

Before you configure the switches for RSTP, be sure you have:

Overview and Topology

RSTP works by identifying certain links as point to point links and blocking other possible paths. When one of the point-to-point links fails, a designated alternate link transitions to the forwarding state and take over. Configuring nonstop bridging (NSB) on a switch with redundant Routing Engines keeps RSTP synchronized on both Routing Engines. This way, RSTP remains active immediately after a switchover because it is already synchronized to the backup Routing Engine. RSTP does not have to reconverge after a Routing Engine switchover when NSB is enabled because the neighbor devices do not detect an RSTP change on the switch. In this example, four EX Series switches are connected in the topology displayed in Figure 1 to create a loop-free topology with NSB applied to switches with dual Routing Engines.

Figure 1: Network Topology for RSTPNetwork Topology for RSTP

Table 1 shows the components of the topology for this example.

Note:

You can configure RSTP only on physical interfaces, not on logical interfaces.

Table 1: Components of the Topology for Configuring RSTP

Property

Settings

Switch 1

The following interfaces on Switch 1 are connected in this way:

  • ge-0/0/9 is connected to Switch 2

  • ge-0/0/13 is connected to Switch 4

  • ge-0/0/11 is connected to Switch 3

Switch 2

The following interfaces on Switch 2 are connected in this way:

  • ge-0/0/14 is connected to Switch 1

  • ge-0/0/18 is connected to Switch 3

Switch 3

The following interfaces on Switch 3 are connected in this way:

  • ge-0/0/26 is connected to Switch 1

  • ge-0/0/28 is connected to Switch 2

  • ge-0/0/24 is connected to Switch 4

Switch 4

The following interfaces on Switch 4 are connected in this way:

  • ge-0/0/19 is connected to Switch 1

  • ge-0/0/23 is connected to Switch 3

VLAN names and tag IDs

voice-vlan, tag 10

employee-vlan, tag 20

guest-vlan, tag 30

camera-vlan, tag 40

This configuration example creates a loop-free topology between four EX Series switches using RSTP.

An RSTP topology contains ports that have specific roles:

  • The root port is responsible for forwarding data to the root bridge.

  • The alternate port is a standby port for the root port. When a root port goes down, the alternate port becomes the active root port.

  • The designated port forwards data to the downstream network segment or device.

  • The backup port is a backup port for the designated port. When a designated port goes down, the backup port becomes the active designated port and starts forwarding data.

Note:

You also can create a loop-free topology between the aggregation layer and the distribution layer using redundant trunk links. For more information about configuring redundant trunk links, see Example: Configuring Redundant Trunk Links for Faster Recovery on Devices with ELS Support.

Topology

Configuring RSTP and Nonstop Bridging on Switch 1

Procedure

CLI Quick Configuration

To quickly configure RSTP and nonstop bridging on Switch 1, copy the following commands and paste them into the switch terminal window:

If Switch 1 includes dual Routing Engines, configure NSB. To quickly configure nonstop bridging on Switch 1, copy the following commands and paste them into the switch terminal window:

Note:

NFX150 devices support only a single Routing Engine.

Step-by-Step Procedure

To configure RSTP and nonstop bridging on Switch 1:

  1. Configure the VLANs voice-vlan, employee-vlan, guest-vlan, and camera-vlan:

  2. Configure the VLANs on the interfaces, including support for the Ethernet switching protocol:

  3. Configure the port mode for the interfaces:

  4. Configure RSTP on the switch:

Step-by-Step Procedure

If Switch 1 includes dual Routing Engines, configure nonstop bridging. To configure NSB on Switch 1:

  1. Enable graceful Routing Engine switchover (GRES):

  2. Configure the switch to always synchronize configuration changes between the Routing Engines:

    If you try to commit a configuration in which nonstop bridging is configured but synchronization of configuration changes is not configured, the configuration is not committed.

  3. Enable nonstop bridging:

    Note:

    This process enables NSB for all NSB-supported Layer 2 protocols on the switch, including RSTP.

Results

Check the results of the configuration:

Configuring RSTP and Nonstop Bridging on Switch 2

Procedure

CLI Quick Configuration

To quickly configure RSTP and nonstop bridging on Switch 2, copy the following commands and paste them into the switch terminal window:

Note:

Starting with Junos OS Release 15.1 for EX Series and QFX Series switches with support for the Enhanced Layer 2 Software (ELS) configuration style, you can configure spanning tree parameters globally on all spanning tree interfaces. See Configuring RSTP on EX Series Switches (CLI Procedure) for additional information.

If Switch 2 includes dual Routing Engines, configure NSB. To quickly configure nonstop bridging on Switch 2, copy the following commands and paste them into the switch terminal window:

Step-by-Step Procedure

To configure RSTP and nonstop bridging on Switch 2:

  1. Configure the VLANs voice-vlan, employee-vlan, guest-vlan, and camera-vlan:

  2. Configure the VLANs on the interfaces, including support for the Ethernet switching protocol:

  3. Configure the port mode for the interfaces:

  4. Configure RSTP on the switch:

Step-by-Step Procedure

If Switch 2 includes dual Routing Engines, configure nonstop bridging. To configure NSB on Switch 2:

  1. Enable graceful Routing Engine switchover (GRES):

  2. Configure the switch to always synchronize configuration changes between the Routing Engines:

    If you try to commit a configuration in which nonstop bridging is configured but synchronization of configuration changes is not configured, the configuration is not committed.

  3. Enable nonstop bridging:

    Note:

    This process enables NSB for all NSB-supported Layer 2 protocols on the switch, including RSTP.

Results

Check the results of the configuration:

Configuring RSTP and Nonstop Bridging on Switch 3

Procedure

CLI Quick Configuration

To quickly configure RSTP and nonstop bridging on Switch 3, copy the following commands and paste them into the switch terminal window:

If Switch 3 includes dual Routing Engines, configure NSB. To quickly configure nonstop bridging on Switch 3, copy the following commands and paste them into the switch terminal window:

Step-by-Step Procedure

To configure RSTP and nonstop bridging on Switch 3:

  1. Configure the VLANs voice-vlan, employee-vlan, guest-vlan, and camera-vlan:

  2. Configure the VLANs on the interfaces, including support for the Ethernet switching protocol:

  3. Configure the port mode for the interfaces:

  4. Configure RSTP on the switch:

Step-by-Step Procedure

If Switch 3 includes dual Routing Engines, configure nonstop bridging. To configure NSB on Switch 3:

  1. Enable graceful Routing Engine switchover (GRES):

  2. Configure the switch to always synchronize configuration changes between the Routing Engines:

    If you try to commit a configuration in which nonstop bridging is configured but synchronization of configuration changes is not configured, the configuration is not committed.

  3. Enable nonstop bridging:

    Note:

    This process enables NSB for all NSB-supported Layer 2 protocols on the switch, including RSTP.

Results

Check the results of the configuration:

Configuring RSTP and Nonstop Bridging on Switch 4

Procedure

CLI Quick Configuration

To quickly configure RSTP and nonstop bridging on Switch 4, copy the following commands and paste them into the switch terminal window:

If Switch 4 includes dual Routing Engines, configure NSB. To quickly configure nonstop bridging on Switch 4, copy the following commands and paste them into the switch terminal window:

Step-by-Step Procedure

To configure RSTP and nonstop bridging on Switch 4:

  1. Configure the VLANs voice-vlan, employee-vlan, guest-vlan, and camera-vlan:

  2. Configure the VLANs on the interfaces, including support for the Ethernet switching protocol:

  3. Configure the port mode for the interfaces:

  4. Configure RSTP on the switch:

Step-by-Step Procedure

If Switch 4 includes dual Routing Engines, configure nonstop bridging. To configure NSB on Switch 4:

  1. Enable graceful Routing Engine switchover (GRES):

  2. Configure the switch to always synchronize configuration changes between the Routing Engines:

    If you try to commit a configuration in which nonstop bridging is configured but synchronization of configuration changes is not configured, the configuration is not committed.

  3. Enable nonstop bridging:

    Note:

    This process enables NSB for all NSB-supported Layer 2 protocols on the switch, including RSTP.

Results

Check the results of the configuration:

Verification

To confirm that the configuration is working properly, perform these tasks on both Routing Engines:

Verifying RSTP Configuration on Switch 1

Purpose

Verify the RSTP configuration on Switch 1.

Action

Use the operational mode command:

Meaning

The operational mode command show spanning-tree interface shows that ge-0/0/13 is in a forwarding state. The other interfaces on Switch 1 are blocking.

Verifying RSTP Configuration on Switch 2

Purpose

Use this procedure to verify the RSTP configuration on both Switch 2 Routing Engines.

Action

Use the operational mode command:

Meaning

The operational mode command show spanning-tree interface shows that ge-0/0/18 is in a forwarding state and is the root port.

Verifying RSTP Configuration on Switch 3

Purpose

Use this procedure to verify the RSTP configuration on both Switch 3 Routing Engines.

Action

Use the operational mode commands:

Meaning

The operational mode command show spanning-tree interface shows that no interface is the root interface.

Verifying RSTP Configuration on Switch 4

Purpose

Use this procedure to verify the RSTP configuration on both Switch 4 Routing Engines.

Action

Use the operational mode commands:

Meaning

The operational mode command show spanning-tree interface shows that interface ge-0/0/23 is the root interface and forwarding.

Example: Faster Convergence and Improved Network Stability with RSTP on EX Series Switches

EX Series switches use Rapid Spanning Tree Protocol (RSTP) by default to provide a loop-free topology.

When switches that support redundant Routing Engines use RSTP, it is important to keep RSTP synchronized on both Routing Engines so that no loss of service occurs after a Routing Engine switchover. Nonstop bridging protocol keeps Routing Engines synchronized.

This example describes how to configure RSTP and NSB on four EX Series switches:

Requirements

This example uses the following hardware and software components:

  • Junos OS Release 11.3 or later for EX Series switches

  • Four EX Series switches

Before you configure the switches for RSTP, be sure you have:

Overview and Topology

RSTP works by identifying certain links as point to point links and blocking other possible paths. When one of the point-to-point links fails, a designated alternate link transitions to the forwarding state and take over. Configuring nonstop bridging (NSB) on a switch with redundant Routing Engines keeps RSTP synchronized on both Routing Engines. This way, RSTP remains active immediately after a switchover because it is already synchronized to the backup Routing Engine. RSTP does not have to reconverge after a Routing Engine switchover when NSB is enabled because the neighbor devices do not detect an RSTP change on the switch. In this example, four EX Series switches are connected in the topology displayed in Figure 2 to create a loop-free topology with NSB applied to switches with dual Routing Engines.

Figure 2: Network Topology for RSTPNetwork Topology for RSTP

Table 2 shows the components of the topology for this example.

Note:

You can configure RSTP on logical or physical interfaces. This example shows RSTP configured on logical interfaces.

Table 2: Components of the Topology for Configuring RSTP

Property

Settings

Switch 1

The following interfaces on Switch 1 are connected in this way:

  • ge-0/0/9 is connected to Switch 2

  • ge-0/0/13 is connected to Switch 4

  • ge-0/0/11 is connected to Switch 3

Switch 2

The following interfaces on Switch 2 are connected in this way:

  • ge-0/0/14 is connected to Switch 1

  • ge-0/0/18 is connected to Switch 3

Switch 3

The following interfaces on Switch 3 are connected in this way:

  • ge-0/0/26 is connected to Switch 1

  • ge-0/0/28 is connected to Switch 2

  • ge-0/0/24 is connected to Switch 4

Switch 4

The following interfaces on Switch 4 are connected in this way:

  • ge-0/0/19 is connected to Switch 1

  • ge-0/0/23 is connected to Switch 3

VLAN names and tag IDs

voice-vlan, tag 10

employee-vlan, tag 20

guest-vlan, tag 30

camera-vlan, tag 40

This configuration example creates a loop-free topology between four EX Series switches using RSTP.

An RSTP topology contains ports that have specific roles:

  • The root port is responsible for forwarding data to the root bridge.

  • The alternate port is a standby port for the root port. When a root port goes down, the alternate port becomes the active root port.

  • The designated port forwards data to the downstream network segment or device.

  • The backup port is a backup port for the designated port. When a designated port goes down, the backup port becomes the active designated port and starts forwarding data.

Note:

You also can create a loop-free topology between the aggregation layer and the distribution layer using redundant trunk links. For more information about configuring redundant trunk links, see Example: Configuring Redundant Trunk Links for Faster Recovery on EX Series Switches.

Topology

Configuring RSTP and Nonstop Bridging on Switch 1

Procedure

CLI Quick Configuration

To quickly configure RSTP and nonstop bridging on Switch 1, copy the following commands and paste them into the switch terminal window:

If Switch 1 includes dual Routing Engines, configure NSB. To quickly configure nonstop bridging on Switch 1, copy the following commands and paste them into the switch terminal window:

Step-by-Step Procedure

To configure RSTP and nonstop bridging on Switch 1:

  1. Configure the VLANs voice-vlan, employee-vlan, guest-vlan, and camera-vlan:

  2. Configure the VLANs on the interfaces, including support for the Ethernet switching protocol:

  3. Configure the port mode for the interfaces:

  4. Configure RSTP on the switch:

Step-by-Step Procedure

If Switch 1 includes dual Routing Engines, configure nonstop bridging. To configure NSB on Switch 1:

  1. Enable graceful Routing Engine switchover (GRES):

  2. Configure the switch to always synchronize configuration changes between the Routing Engines:

    If you try to commit a configuration in which nonstop bridging is configured but synchronization of configuration changes is not configured, the configuration is not committed.

  3. Enable nonstop bridging:

    Note:

    This process enables NSB for all NSB-supported Layer 2 protocols on the switch, including RSTP.

Results

Check the results of the configuration:

Configuring RSTP and Nonstop Bridging on Switch 2

Procedure

CLI Quick Configuration

To quickly configure RSTP and nonstop bridging on Switch 2, copy the following commands and paste them into the switch terminal window:

If Switch 2 includes dual Routing Engines, configure NSB. To quickly configure nonstop bridging on Switch 2, copy the following commands and paste them into the switch terminal window:

Step-by-Step Procedure

To configure RSTP and nonstop bridging on Switch 2:

  1. Configure the VLANs voice-vlan, employee-vlan, guest-vlan, and camera-vlan:

  2. Configure the VLANs on the interfaces, including support for the Ethernet switching protocol:

  3. Configure the port mode for the interfaces:

  4. Configure RSTP on the switch:

Step-by-Step Procedure

If Switch 2 includes dual Routing Engines, configure nonstop bridging. To configure NSB on Switch 2:

  1. Enable graceful Routing Engine switchover (GRES):

  2. Configure the switch to always synchronize configuration changes between the Routing Engines:

    If you try to commit a configuration in which nonstop bridging is configured but synchronization of configuration changes is not configured, the configuration is not committed.

  3. Enable nonstop bridging:

    Note:

    This process enables NSB for all NSB-supported Layer 2 protocols on the switch, including RSTP.

Results

Check the results of the configuration:

Configuring RSTP and Nonstop Bridging on Switch 3

Procedure

CLI Quick Configuration

To quickly configure RSTP and nonstop bridging on Switch 3, copy the following commands and paste them into the switch terminal window:

If Switch 3 includes dual Routing Engines, configure NSB. To quickly configure nonstop bridging on Switch 3, copy the following commands and paste them into the switch terminal window:

Step-by-Step Procedure

To configure RSTP and nonstop bridging on Switch 3:

  1. Configure the VLANs voice-vlan, employee-vlan, guest-vlan, and camera-vlan:

  2. Configure the VLANs on the interfaces, including support for the Ethernet switching protocol:

  3. Configure the port mode for the interfaces:

  4. Configure RSTP on the switch:

Step-by-Step Procedure

If Switch 3 includes dual Routing Engines, configure nonstop bridging. To configure NSB on Switch 3:

  1. Enable graceful Routing Engine switchover (GRES):

  2. Configure the switch to always synchronize configuration changes between the Routing Engines:

    If you try to commit a configuration in which nonstop bridging is configured but synchronization of configuration changes is not configured, the configuration is not committed.

  3. Enable nonstop bridging:

    Note:

    This process enables NSB for all NSB-supported Layer 2 protocols on the switch, including RSTP.

Results

Check the results of the configuration:

Configuring RSTP and Nonstop Bridging on Switch 4

Procedure

CLI Quick Configuration

To quickly configure RSTP and nonstop bridging on Switch 4, copy the following commands and paste them into the switch terminal window:

If Switch 4 includes dual Routing Engines, configure NSB. To quickly configure nonstop bridging on Switch 4, copy the following commands and paste them into the switch terminal window:

Step-by-Step Procedure

To configure RSTP and nonstop bridging on Switch 4:

  1. Configure the VLANs voice-vlan, employee-vlan, guest-vlan, and camera-vlan:

  2. Configure the VLANs on the interfaces, including support for the Ethernet switching protocol:

  3. Configure the port mode for the interfaces:

  4. Configure RSTP on the switch:

Step-by-Step Procedure

If Switch 4 includes dual Routing Engines, configure nonstop bridging. To configure NSB on Switch 4:

  1. Enable graceful Routing Engine switchover (GRES):

  2. Configure the switch to always synchronize configuration changes between the Routing Engines:

    If you try to commit a configuration in which nonstop bridging is configured but synchronization of configuration changes is not configured, the configuration is not committed.

  3. Enable nonstop bridging:

    Note:

    This process enables NSB for all NSB-supported Layer 2 protocols on the switch, including RSTP.

Results

Check the results of the configuration:

Verification

To confirm that the configuration is working properly, perform these tasks on both Routing Engines:

Verifying RSTP Configuration on Switch 1

Purpose

Verify the RSTP configuration on Switch 1.

Action

Use the operational mode command:

Meaning

The operational mode command show spanning-tree interface shows that ge-0/0/13.0 is in a forwarding state. The other interfaces on Switch 1 are blocking.

Verifying RSTP Configuration on Switch 2

Purpose

Use this procedure to verify the RSTP configuration on both Switch 2 Routing Engines.

Action

Use the operational mode command:

Meaning

The operational mode command show spanning-tree interface shows that ge-0/0/18.0 is in a forwarding state and is the root port.

Verifying RSTP Configuration on Switch 3

Purpose

Use this procedure to verify the RSTP configuration on both Switch 3 Routing Engines.

Action

Use the operational mode commands:

Meaning

The operational mode command show spanning-tree interface shows that no interface is the root interface.

Verifying RSTP Configuration on Switch 4

Purpose

Use this procedure to verify the RSTP configuration on both Switch 4 Routing Engines.

Action

Use the operational mode commands:

Meaning

The operational mode command show spanning-tree interface shows that interface ge-0/0/23.0 is the root interface and forwarding.

Forcing RSTP or VSTP to Run as IEEE 802.1D STP (CLI Procedure)

Note:

This procedure uses Junos OS for EX Series switches with support for the Enhanced Layer 2 Software (ELS) configuration style. For ELS details, see Using the Enhanced Layer 2 Software CLI.

On EX Series switches running Rapid Spanning Tree Protocol (RSTP) (the default) or VLAN Spanning Tree Protocol (VSTP), you can force the original IEEE 802.1D Spanning Tree Protocol (STP) version to run in place of RSTP or VSTP. Configure the force-version stp statement for compatibility with older bridges that do not support RSTP or VSTP.

To force the spanning-tree protocol version to be the original IEEE 802.1D STP:

Enable IEEE 802.1D STP:
Note:

After using the force-version statement to enable xSTP globally, apply the force-version statement for specific Layer 2 ports.

Release History Table
Release
Description
15.1
Starting with Junos OS Release 15.1 for EX Series and QFX Series switches with support for the Enhanced Layer 2 Software (ELS) configuration style, you can configure spanning tree parameters globally on all spanning tree interfaces.