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Configuring Spanning Tree on Meraki Switches (MS)

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Network-wide STP settings, including enabling RSTP and setting the bridge priority on MS switches, can be configured in the Meraki Dashboard. Port level STP settings, including enabling or disabling RSTP on a port and configuring STP guards, can also be configured.

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Configuring STP Globally

Network-wide STP configurations can be made from the STP configurations section of the Switch settings page on the dashboard. To get to this section:

1. Navigate to Switch > Configure > Switch settings.

Navigate to Switch Settings.png

2. Scroll to the STP configuration section.

STP Configuration Section.png

Enable RSTP Globally

To disable or enable RSTP globally, select Enable RSTP or Disable RSTP.

Enable RSTP Globably.png

Option Description
Enable RSTP Enabling RSTP globally allows all of the switches in the network to participate in Spanning Tree processes. RSTP is enabled globally by default; individual ports can be configured to disable RSTP. It is recommended that RSTP remain enabled. 
Disable RSTP RSTP may be disabled globally. Disabling RSTP globally removes all the switches in the network from participating any STP processing including any STP guard configuration. Disabling RSTP is not recommended. When RSTP is disabled globally, no ports may be configured to enable RSTP.

Please note: MS390 runs single instance (0), single region (region1), and single revision (revision 1) MSTP. This is essentially Rapid Spanning-Tree. Please make sure for interoperability with any other non-Meraki platforms, to either run Rapid Spanning-tree or MSTP (not PVST or any iteration, nor any other vendor specific STP implementation). This will ensure that there are no issues with compatibility and functionality.

Example of an IOS device compatible configuration:
spanning-tree mode mst
spanning-tree mst configuration
 name region1
 revision 1
spanning-tree mst 0 priority 4096

Set Bridge Priority

You can configure the STP bridge priority of any Meraki switch in your network from the STP bridge priority field.

1. Select Set the bridge priority for another switch or stack.

Set Bridge Priority.png

2. Under Switches/Stacks, enter the name of the switch or switch stack on which you want to configure the STP priority.

Choose Switches.png

3. In the dropdown under the Bridge priority, select the STP priority that you would like to assign to the switch.

Select Bridge Priority.png

The default priority for all Meraki switches is 32768. It is recommended that you set the priority of your desired root bridge to 4096 to ensure its election. The root bridge should be a switch in the center of the network, near high traffic sources (such as servers), to optimize traffic flow across the network. Using priority 0 is also acceptable for the root, but leaves no room for modification when replacing a core switch in production or modifying behavior temporarily.

It is best practices to set a layered approach to the STP priorities in a network. For instance, if there is a clear Core <> Distribution <> Access Layer, priorities should be Core (4096), Distribution (16384), and Access (61440). At no point in a production network should you leave the any switch at its default configurations. 

Reset a Bridge Priority

To remove an STP priority configuration from a Meraki switch and restore the default priority value, select the X to the right of the priority configuration.

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Save Changes to Global STP Configuration

Select Save at the bottom of the page.

Switch Setting Save.png

Configure Port Level STP

Port level STP configurations can be made from the switch port configuration menu from the dashboard. To access the switch port configuration menu:

1. Navigate to Switch > Monitor > Switch ports.

Switch Ports Navigation.png

2. Choose the port(s) you wish to configure by selecting the box(es) to the left of the port name(s).

Selected Ports.png

3. Select Edit at the top of the page.

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The switch port configuration menu will then be displayed.

Switchport Config Menu.png

Enabling RSTP on a Switch Port

In the RSTP field of the switch port configuration menu, you may select Enabled or Disabled.

RTSP Port Options.png

Option Description
Enabled

RSTP must be enabled globally (see "Enable RSTP Globally") for any ports to be able to participate in Spanning Tree processes. When RSTP is enabled globally, RSTP will be enabled at the port level by default.

A disabled port can be re-enabled by selecting Enabled. While RSTP is enabled on a switch port, that port is able to participate in Spanning Tree processes. It is recommended that RSTP be enabled on all ports.
Disabled RSTP may be disabled at the port level. Disabling RSTP on a port removes the port from any STP processing including any STP guard configuration. Disabling RSTP on a port is not recommended unless the client device connected to the port is incompatible with STP. If RSTP is disabled globally, all ports will have RSTP disabled and cannot have it enabled.

Configuring STP Guard on a Switch Port

From the drop-down in the STP guard configuration option, you may select Disabled, Root guard, BPDU guard, or Loop guard.

STP Guard Options.png

Option Description
Disabled STP Guard is disabled by default. It applies no STP guard functionality to the port.
Root guard Root guard is used to protect the Spanning Tree topology of a network by enforcing the location of the Root Bridge. If a port with Root Guard enabled on it receives a superior BPDU, the port will transition into an STP-inconsistent state. In this state, the port will still process BPDUs but will not learn MAC addresses or forward traffic. It is recommended that Root Guard be applied to ports connecting to neighboring, downstream switches that should not be the Root Bridge, to prevent a superior BPDU from being received on the port and causing the election of an unexpected Root Bridge.
BPDU guard BPDUs - Bridge Protocol Data Units - are informational messages communicated between all switches in a Spanning Tree instance to maintain STP consistency. BPDU Guard is used to protect the Spanning Tree topology of a network by enforcing STP domain borders. If a port with BPDU Guard enabled on it receives a BPDU, the port will transition to a disabled state. It is recommended that BPDU Guard be applied to all access ports or client-facing ports that are not intended to be connected to a neighboring switch.
Loop guard Loop guard is used to protect a network from unidirectional loops. A unidirectional link failure may stop a port in the blocking state from receiving BPDUs causing it to erroneously transition the forwarding state, creating a loop in the network. If a non-designated port with Loop Guard enabled stops receiving BPDUs, it will transition into a loop-inconsistent blocking state. In this state, the port will still process BPDUs but will not learn MAC addresses or forward traffic, thereby preventing a loop from forming. It is recommended that Loop Guard be enabled on non-designated fiber ports in physically redundant topologies. It is also recommended that Loop Guard be paired with Unidirectional Link Detection (UDLD). For more information on UDLD, check out our Unidirectional Link Detection article.

Save Changes to a Switch Port’s STP Configuration

Select Update at the bottom of the switch port configuration menu to save your configuration.

Switchport Update.png