Users Guide
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Spanning Tree Protocol (STP)
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.
Protocol Overview
By eliminating loops, the protocol 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 STP, can cause
unnecessarily high switch CPU utilization and memory consumption.
Dell Networking OS supports three other variations of spanning tree, as shown in the following table.
Table 83. 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
Related Conguration Tasks
• Adding an Interface to the Spanning Tree Group
• Modifying Global Parameters
• Modifying Interface STP Parameters
• Enabling PortFastt
• Prevent Network Disruptions with BPDU Guard
• STP Root Guard
• Enabling SNMP Traps for Root Elections and Topology Changes
• Conguring Spanning Trees as Hitless
Important Points to Remember
• STP is disabled by default.
• The Dell Networking OS supports only one spanning tree instance (0). For multiple instances, enable the multiple spanning tree
protocol (MSTP) or per-VLAN spanning tree plus (PVST+). You may only enable one avor of spanning tree at any one time.
• All ports in virtual local area networks (VLANs) and all enabled interfaces in Layer 2 mode are automatically added to the
spanning tree topology at the time you enable the protocol.
Spanning Tree Protocol (STP)
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