Skip to content
Any configuration changes made locally on the switch won't be synchronized with Sophos Central. We recommend making changes from the Sophos Central control panel instead.

Page permalink

Always use the following permalink when referencing this page. It will remain unchanged in future help versions.

https://docs.sophos.com/nsg/switch/help/en-us/index.html?contextId=user-guide-features-configure-STP

STP

Spanning Tree Protocol (STP) prevents network loops by exchanging Bridge Protocol Data Units (BPDUs) with other switches on the network. BPDUs contain information about ports and switches on the network. The switches use this information to make sure only one route exists between two destinations and create backup routes in case the primary route fails.

Go to Configure > STP to configure Global settings, see Root bridge information, and configure Rapid Spanning Tree Protocol (RSTP) and Multiple Spanning Tree Protocol (MSTP) settings.

Global settings

The Global settings tab lets you turn STP on or off, configure settings such as BPDU forwarding, STP version, priority, and delay, and see the root bridge details.

You can configure the following settings:

  • STP state: Select Turned on or Turned off to set the STP status of the switch.
  • BPDU forwarding: Select Turned on or Turned off to set the BPDU forwarding status of the switch.

Restriction

You can't turn on STP state and BPDU forwarding at the same time.

  • Forced version: Select the version of STP from the following options:

    • MSTP: Multiple Spanning Tree Protocol (MSTP) is suitable for larger networks and VLANs because it allows for the creation of multiple spanning trees. It supports independent spanning trees based on VLAN groups, load balancing, and provides multiple forwarding paths for traffic.
    • RSTP: Rapid Spanning Tree Protocol (RSTP) is a faster replacement for the legacy STP. It's also faster than MSTP and better for smaller networks, but only creates a single spanning tree regardless of network size.

  • Configuration name: Enter the MSTP Configuration name, using a maximum of 32 characters. The default configuration name is the switch's MAC address.

  • Configuration revision: Enter the MSTP revision level from 0 to 65535. The default is 0.
  • Priority: Select the priority of the switch from the drop-down list. The switch with the lowest priority in the network is the root bridge.
  • Forward delay: Set the time, in seconds, the switch spends in the listen and learn state before changing states. Select a time from the drop-down menu. The default is 15.
  • Maximum age: Set the maximum time, in seconds, the switch waits to receive a BPDU from the root bridge. Select a time from the drop-down list. The default is 20.
  • Tx hold count: Set the maximum BPDUs sent per second. The default is 6.
  • Hello time: Set the interval, in seconds, at which the switch sends BPDUs on a port. The default is 2.

Click Apply to save the settings or Reset to clear the settings.

Root bridge information

The root bridge is the root of the tree within a spanning tree network and is the switch from which all spanning tree calculations are made. The root bridge is elected based on its Bridge ID (BID), which is based on the switch's priority and its MAC address. All switches listen for BPDUs sent from the root bridge.

You can see the following information about the root bridge:

  • Bridge address: Shows the MAC address of the bridge with the lowest path cost to the root bridge.
  • Root address: Shows the MAC address of the root bridge.
  • Priority: Shows the priority of the root bridge.
  • Cost: Shows the cost of the path with the lowest cost, based on bandwidth, to reach the root bridge.
  • Port: Shows the port on the switch connected to the path that leads to the root bridge.
  • Forward delay: Shows the time, in seconds, the switch spends in the listen and learn state before changing states.
  • Maximum age: Shows the time the switch waits to receive a BPDU from the root bridge.
  • Hello time: Shows the interval, in seconds, at which the root bridge sends BPDUs.

More resources