Guides network administrators through configuring and managing Spanning Tree Protocol to prevent loops and ensure redundant connectivity in switched network topologies.
Spanning Tree Protocol
This topic explains the Spanning Tree Protocol (STP), a Layer 2 link management protocol that provides path redundancy and prevents loops in Ethernet networks, ensuring network stability and proper operation.
Establish the STP using BPDUs
Learn how to establish the Spanning Tree topology in a Layer 2 network using Bridge Protocol Data Units (BPDUs) to ensure a loop-free path and assign port roles.
BPDU exchange results
This topic explains the actions that result from a BPDU exchange in a switched network, including root switch election, port selection, and path blocking in the Spanning Tree topology.
STP port roles
This topic explains the roles assigned to ports by the Spanning Tree algorithm and how these roles affect network topology and redundancy.
Bridge ID and switch priority
This topic explains the concept of Bridge ID and Switch Priority in IEEE 802.1D, describing how each switch and VLAN is uniquely identified and how the bridge ID is constructed.
Port priority and path cost
This topic explains how Spanning Tree port priority and path cost settings determine which switch port is placed in the forwarding or blocking state when a loop occurs, and describes how these values influence interface selection.
Spanning Tree interface states
Lists the five states that layer 2 interfaces can exist in when using Spanning Tree protocol.
How a switch becomes the root switch
This process describes how a switch is elected as the root switch in a network using default spanning-tree settings and how the root switch can be changed by adjusting switch priority.
STP and redundant connectivity
This topic explains how spanning tree protocol enables redundant connectivity between switches by automatically managing link states to prevent loops and ensure network reliability.
Spanning Tree address management
This topic explains how IEEE 802.1D defines and manages multicast addresses for Spanning Tree protocols, including address handling and forwarding behavior on switches depending on the spanning-tree state.
Accelerated aging to retain connectivity
This topic explains how accelerated aging is used to retain network connectivity by reducing the address-aging time during spanning-tree reconfiguration events, allowing dynamic addresses to be quickly relearned and minimizing connectivity loss.
Spanning Tree modes and protocols
This topic explains the spanning-tree modes and protocols supported by the switch, including PVST+, Rapid PVST+, and MSTP, and describes their key features and differences.
Spanning Tree instances
This topic explains the supported spanning-tree instances for PVST+, Rapid PVST+, and MSTP modes on the Switch or Switch stack.
Spanning Tree interoperability and backward compatibility
This topic explains interoperability and backward compatibility considerations for Spanning Tree Protocols (PVST+, MSTP, and Rapid PVST+) in mixed network environments.
Spanning Tree and switch stacks
This topic explains how Spanning Tree operates in switch stacks, including the behavior of bridge IDs, stack root election, and reconvergence scenarios when switches join or leave the stack or network.
Configuration guidelines
Provides guidelines for configuring system parameters to ensure optimal performance and stability. These standards help administrators maintain consistent settings across the network infrastructure.
Default configuration
This topic explains the default configuration settings for Spanning Tree features, including enable state, mode, priorities, port costs, and timers on Cisco devices.
Configure Spanning Tree mode
Learn how to change the spanning-tree mode from the default Rapid PVST+ to PVST+ or MSTP to meet your network's convergence and VLAN scalability requirements.
Disable Spanning Tree on VLANs
Learn how to disable spanning tree on specific VLANs when you are certain there are no loops in the network topology. Use this procedure to prevent Spanning Tree protection where it is not needed, but exercise caution to avoid network issues.
Configure the root switch
Learn how to configure a switch as the root for a specified VLAN by modifying its priority to ensure optimal network traffic flow and convergence.
Configure the secondary root switch
Learn how to configure a switch as the secondary root by modifying its priority, ensuring it becomes the root switch if the primary fails and other switches use the default priority.
Configure port priority for an interface
Learn how to configure the port priority for an interface to control which interface spanning tree selects when a loop occurs.
Configure path cost for an interface
Learn how to configure the path cost for an interface to control which interface spanning tree places into the forwarding state when a loop occurs.
Configure VLAN switch priority
Learn how to configure the switch priority to influence root switch selection in a stand-alone or stacked environment.
Configure VLAN hello time
Learn how to configure the hello time of a VLAN to control the interval between configuration messages generated and sent by the root Switch.
Configure VLAN forward delay time
Learn how to configure the forward time of a VLAN to control how long an interface waits before changing from its spanning-tree learning and listening states to the forwarding state.
Configure the maximum-aging time for a VLAN
Learn how to configure the maximum-aging time of a VLAN to control how long a switch waits without receiving Spanning Tree configuration messages before reconfiguration.
Configure the transmit hold-count
Learn how to configure the transmit hold-count to control the BPDU burst size and manage the number of BPDUs sent before pausing.
Monitor Spanning Tree status
This topic explains how to display and clear Spanning Tree status using various show and clear commands on active interfaces, VLANs, and portfast configurations.
Additional references for STP
Describes supplementary documentation and resources that provide further information about Spanning Tree Protocol (STP) configuration, troubleshooting, and best practices beyond the scope of this guide.
Feature information for STP
Describes the introduction of STP (Spanning Tree Protocol) feature modifications in Cisco IOS XE Release 17.18.1, providing enhanced network loop prevention and topology management capabilities.