Concept Guide
Spanning Tree Protocol (STP)
The spanning tree protocol (STP) is a Layer 2 protocol — specied by IEEE 802.1d — that eliminates loops in a bridged topology by
enabling only a single path through the network.
Topics:
• Protocol Overview
• Congure Spanning Tree
• Important Points to Remember
• Conguring Interfaces for Layer 2 Mode
• Enabling Spanning Tree Protocol Globally
• Adding an Interface to the Spanning Tree Group
• Modifying Global Parameters
• Modifying Interface STP Parameters
• Enabling PortFast
• Preventing Network Disruptions with BPDU Guard
• Selecting STP Root
• STP Root Guard
• Enabling SNMP Traps for Root Elections and Topology Changes
• STP Loop Guard
• Displaying STP Guard Conguration
Protocol Overview
By eliminating loops, STP improves scalability in a large network and allows you to implement redundant paths, which can be activated after
the failure of active paths. Layer 2 loops, which can occur in a network due to poor network design and without enabling protocols like
xSTP, can cause unnecessarily high switch CPU utilization and memory consumption.
The system supports three other versions of spanning tree, as shown in the following table.
Table 125. Dell Networking OS Supported Spanning Tree Protocols
Dell Networking Term IEEE Specication
Spanning Tree Protocol (STP) 802.1d
Rapid Spanning Tree Protocol (RSTP) 802.1w
Multiple Spanning Tree Protocol (MSTP) 802.1s
Per-VLAN Spanning Tree Plus (PVST+) Third Party
Congure Spanning Tree
Conguring spanning tree is a two-step process.
• Conguring Interfaces for Layer 2 Mode
• Enabling Spanning Tree Protocol Globally
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1024 Spanning Tree Protocol (STP)