• Switch 1.3.0
• Product Overview
  • Package Contents
  • Technical Specifications
  • Supported SonicWall and third-party SFP and SFP+ Modules
  • Physical Interface - 8 Port Switch
  • Physical Interface - 10 Port Switch
  • Physical Interface - 24 Port Switch
  • Physical Interface - 48 Port Switch
  • Device Management
  • Connecting the Switch to a Network
  • Capacity Matrix
• System Management
  • System
    • Dashboard
    • Network
    • Administration
      • SSH Settings
    • System Information
    • User Management
    • Simple Network Management Protocol
      • Classic diagram of SonicWall Switch for SNMP Testing
      • Add View List
      • Add Target Params
      • Add Target Address
      • Add Notify Setting
      • SNMP Traps/Informs
      • How to configure SNMP on SonicWall Switch
      • SNMP supported OID’s in 1.2.0.1-2s
      • How to Configure SNMP/MIB Browser on Client PC
    • Address Resolution Protocol
      • ARP Table
      • ARP Statistics
    • Authentication
    • Firmware and Settings
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    • Time
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        • 802.1X
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      • Advanced
    • Spanning Tree Protocol
      • Network Loops
      • Global Settings
      • MST Instance Settings
      • STP Port Statistics
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      • Link Aggregation Control Protocol Settings
      • Link Aggregation Control Protocol Timeout
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    • Quality of Service
      • Class of Service Mapping
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      • Advanced Mode
        • Class Mapping
          • Adding a Class Policy
        • Policy Mapping
    • Remote Network Monitoring
      • Stat List
      • Event List
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      • History Log Table
    • Port Statistics
  • Routing
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    • 802.1X Security
      • MAC Authentication Bypass
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      • Statistics
    • Denial of Service
    • ACL Management
      • MAC ACL
      • MAC-Based ACE
      • IPv4 ACL
      • IPv4-Based ACE
  • VLAN
    • 802.1Q
      • Configuring IGMP Snooping Settings
      • Configuring DHCP Snooping Status
      • Configuring Access and Trunks using Standalone access
    • Voice VLAN
      • OUI Settings
      • Port Settings
  • Logging
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      • Local Settings
    • Remote Logging
    • Log Table
  • Diagnostics
    • Ping
    • Trace Route
    • Cable Diagnostics
    • Tech Support Report
• System Maintenance
• Switch Troubleshooting
  • Communication flow between Firewall and Switch before it gets authenticated
• SonicWall Support
  • About This Document

Spanning Tree Protocol

The Spanning Tree Protocol (STP) can be used to detect and disable network loops, and to provide backup links between Switches. This allows the Switch to interact with other bridging devices in your network to ensure that only one route exists between any two stations on the network, and provide backup links which automatically take over when a primary link goes down.

STP provides a tree topology for the Switch. There are different types of Spanning tree versions, supported, including STP IEEE802.1D, Multiple Spanning Tree Protocol (MSTP) IEEE802.1w, and Rapid Spanning Tree Protocol (RSTP) IEEE802.1s. Please note that only one spanning tree can be active on the Switch at a time.

STP is a Layer 2 protocol that runs on Switches. STP allows you to ensure that you do not create loops when you have redundant paths in the network. STP provides a single active path between two devices on a network in order to prevents loops from being formed when the Switch is interconnected via multiple paths.

STP uses a distributed algorithm to select a bridging device that serves as the root for the spanning tree network. It does this by selecting a root port on each bridging device to incur the lowest path cost when forwarding a packet from that device to the root device. It then selects a designated bridging device from each LAN which incurs the lowest path cost when forwarding a packet from that LAN to the root device. Next, all ports connected to designated bridging devices are assigned as designated ports. After determining the lowest cost spanning tree, it enables all root ports and designated ports, disabling all other ports. Network packets are therefore only forwarded between root ports and designated ports, eliminating any possible network loops. STP provides a single active path between two devices on a network in order to prevent loops from being formed when the Switch is interconnected via multiple paths.

Once a stable network topology has been established, all bridges listen for Hello Bridge Protocol Data Units (BPDUs) transmitted from the Root Bridge of the Spanning Tree. If a bridge does not receive a Hello BPDU after a predefined interval (known as the Maximum Age), the bridge will assume that the link to the Root Bridge is down and unavailable. This bridge then initiates negotiations with other bridges to reconfigure the network to reestablish a valid network topology.