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RSTP and MSTP

 

 

 

  

 

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RSTP and MSTP 

Introduction 

Rapid Spanning Tree Protocol (IEEE 802.1w) enhances the Spanning Tree Protocol (IEEE 802.1d) to 

provide rapid convergence on Spanning Tree Group 1. Multiple Spanning Tree Protocol (IEEE 802.1s) 
extends the Rapid Spanning Tree Protocol to provide both rapid convergence and load balancing in a 

VLAN environment. 
The following topics are discussed in this chapter: 

•

Rapid Spanning Tree Protocol (RSTP) 

•

Multiple Spanning Tree Protocol (MSTP) 

Rapid Spanning Tree Protocol 

Rapid Spanning Tree Protocol (RSTP) provides rapid convergence of the spanning tree and provides for 

fast reconfiguration critical for networks carrying delay-sensitive traffic such as voice and video. RSTP 

significantly reduces the time to reconfigure the active topology of the network when changes occur to the 
physical topology or its configuration parameters. RSTP reduces the bridged-LAN topology to a single 

Spanning Tree. 
For more information about Spanning Tree Protocol, see the “Spanning Tree Protocol” chapter in this 

guide.  
RSTP parameters are configured in Spanning Tree Group 1. STP Groups 2-128 do not apply to RSTP, and 

must be cleared. There are new STP parameters to support RSTP, and some values to existing parameters 

are different. 
RSTP is compatible with devices that run 802.1d Spanning Tree Protocol. If the switch detects 802.1d 
BPDUs, it responds with 802.1d-compatible data units. RSTP is not compatible with Per VLAN Spanning 

Tree (PVST) protocol. 

Port state changes 

The port state controls the forwarding and learning processes of Spanning Tree. In RSTP, the port state 

has been consolidated to the following: discarding, learning, and forwarding. 

 RSTP vs. STP port states 

Enabled Blocking Discarding 

Enabled Listening Discarding 

Enabled Learning Learning 

Enabled Forwarding 

Forwarding 

Disabled Disabled Discarding