STP vs RSTP: Detailed Comparison

Rashmi Bhardwaj | Blog,Protocol

One of the major functions in network computing is the creation of redundant and loop free network topologies at data link layer 2 of OSI model. In Ethernet networks several protocols are used to achieve network redundancy and loop prevention. 

Today we look more in detail about two data link layer 2 spanning protocols – Spanning tree protocol (STP) and Rapid spanning tree protocol (RSTP), the advantages and disadvantages of both, their key differences, and similarities.

What is Spanning Tree protocol (STP)

STP is layer 2 (data link layer) protocol which runs on switches and bridges. The IEEE standard 802.1D STP is used to prevent loops while using redundant network switches.


Related: Difference between UTP & STP

Pros and Cons of STP


  • Mature protocol widely used in networks
  • Effective handling of complex topologies and prevention of network loops by blocking redundant links
  • It is a stable network topology which ensures only one path is active at any given time
  • Supported by majority of network devices and easy to configure
  • Does not require any special hardware or software to function


  • Slow convergence timings which could result in network downtimes and performance glitches
  • Lead to insufficient use of network resources by blocking links when they are not causing loops
  • Can’t detect changes in network topology in quick manner which could result in network instability
  • Require manual configuration and management in large networks

What is Rapid Spanning Tree protocol (RSTP) 

RSTP is an enhanced version of STP and was designed to overcome the limitations of STP. The IEEE standard of RSTP is 802.1w. It is backward compatible with its counterpart STP. It averts network loops by blocking ports which are not required or unnecessary.

Related: Rapid Spanning Tree Protocol (RSTP) Explained

Pros and cons of RSTP


  • Faster convergence time to reduce network downtime and performance improvement
  • Detect changes in network topology in quick manner and reconfigure network 
  • Uses link aggregation to provide faster network throughput with redundancy
  • Supports VLANs and faster convergence over VLANs


  • Require new network hardware and software for protocol support
  • Require more memory and processing power to function 
  • More complex to configure and manage

Comparison: STP vs RSTP


  • Both prevent loops into networks by blocking redundant links 
  • Both protocols use root bridge to ascertain active path 
  • Both use metric to determine best path to reach root bridge
  • Both protocols use BPDU (Bridge Protocol Data Unit) messages to reach other network devices
  • Both protocols support VLANs


StandardGoverned by IEEE 802.1D standardGoverned by IEEE 802.1.w standard
ConvergenceSupports slow convergence up to 30 seconds or moreSupports rapid convergence less than 1 second
Ports StatesSupported port states •disabled •blocking •listening •learning •forwardingSupported port states •discarding •learning •forwarding
Port RolesSupported port roles •Root port, Designated port •Non designated / non root portsSupported port roles •Root port •Designated port •Backup port •Alternative port •Non designated ports
TimersMaximum age = 20 Forwarding delay = 15 seconds BPDU timer = 2 secondsMaximum age = 20 Time to detect failure = 6 seconds Forwarding delay = 15 seconds BPDU timer = 2 seconds
Port TypesAll ports are sameEdge – similar to STP port configured with fast port Non-edge – P2P or shared
ScalabilitySupports only one spanning tree per VLANSupports multiple spanning trees per VLANs and per VLAN spanning trees
Forwarding State Transition30 seconds = 2 * forwarding delay (listening + learning) before forwarding starts by port after enablementProposal and agreement handshake on point-to-point links is used instead of timer
Failure Detection20 seconds (Maximum age)20 seconds (Maximum age)
BPDU ProcessingInferior BPDUs are ignored until old BPDU information is expiredOn receiving Inferior BPDU , moves the alternate port to designated port role and sends superior BPDU from this new designated port.
Download: STP vs RSTP comparison table


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