Difference Between RSTP and PVST

RSTP vs PVST

Both RSTP and PVST are variants of the spanning tree protocol. Spanning tree protocol is unique to computers. As a network protocol, it ensures a loop-free topology and prevents bridge loops and ensuing broadcast radiation. The protocol’s design includes spare links as automatic backup in case of an active link failure.

“RSTP” stands for “Rapid Spanning Tree Protocol” while “PVST” does the same for “Per-VLAN Spanning Tree.” RSTP is an improvement of STP (Spanning Tree Protocol) in terms of being newer and faster. The RSTP is able to respond to changes in six seconds. Also, it has all the features of previous Cisco proprietary methods.

It is an IEEE Standard 802.1D and creates a spanning tree within a mesh network of connected Ethernet switches. It disables links which are not elements of the tree and leaves a single active path between two network devices. It also creates a network design to include redundant links as automatic backup paths in case of active link failures.

RSTP has a collection of different ports, namely:

The root port which is a forwarding port that is the best port from Non-root bridge to Root bridge.
The designated port which is the intended port for every LAN segment.
The alternate port, as it name implies, is an alternate path to the root bridge which does not use the root port.
The backup port which is a redundant path to a segment where another bridge port already connects.

RSTP also has four port states which are the following:

Discarding – wherein a port discards information received on the interface, discards frames switched from another interface for forwarding, does not learn MAC addresses, and listens for BPDUs.

Learning – a situation where the switch creates a switching table that will map MAC addresses to a port number. It also happens when a port discards frames received on the interface, discards frames switched from another interface for forwarding, learns MAC addresses, and listens for BPDUs.

Forwarding – wherein a port receives and forwards the frames received on the interface, forwards frames switched from another interface, learns MAC addresses, and listens for BPDUs.
Listening – this is when the switch processes BPDU’s that allow it to determine the network topology.
Disabled – the state when the network administrator has disabled the port from use.
Blocking – happens when the port was blocked to stop a looping condition.

On the other hand, PVST is the original Cisco proprietary. It maintains a spanning tree instance for each individual VLAN configured in the network. It is basically on each VLAN independently. It is based on the 802.1D standard and uses Cisco proprietary ISL trunking protocol. It treats each VLAN as a separate network. It prevents creating a loop by forwarding some VLANs on another trunk. It is the default spanning-tree mode used on all Ethernet port-based VLANs.

PVST is succeeding by Cisco proprietary extensions like BackboneFast, UplinkFast, and PortFast.

Summary:

The RSTP is an improvement on the spanning tree protocol, and it is a standard spanning tree as an IEEE standard while the PVST is a spanning tree protocol as a Cisco proprietary.
PVST is the Cisco counterpart of IEEE’s RSTP.
PVST is usually used on VLANS (or Virtual Local Area Network) while RSTP is often used in LAN.
RSTP operates much like STP with Cisco’s enhancements while PVST is a Cisco proprietary in itself.
PVST deals with VLANs which means it handles more network devices compared to the RSTP.
Compared to the PVST, RSTP has no known property extensions since in itself it already has the enhancements derived from Cisco proprietaries.

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