Difference Between RSTP and PVST

Explanation of RSTP and PVST

Rapid Spanning Tree Protocol (RSTP) and Per-VLAN Spanning Tree (PVST) are two protocols that improve network performance and redundancy by preventing network loops.

Rapid Spanning Tree Protocol (RSTP) and Per-VLAN Spanning Tree Protocol (PVST) are two versions of the Spanning Tree Protocol (STP) that have been developed to address specific network needs and limitations.

Rapid Spanning Tree Protocol (RSTP) is an evolution of the original STP protocol that provides faster convergence times and improved scalability. RSTP works by reducing the number of states that a port can be in, from the original five states of STP down to three states: discarding, learning, and forwarding. This reduction in states allows RSTP to react to network changes more quickly, resulting in faster convergence times and improved network performance.

Per-VLAN Spanning Tree Protocol (PVST) is a Cisco proprietary implementation of STP that allows for multiple instances of STP to be run on a switch, with one instance per VLAN. This allows for faster convergence times on a per-VLAN basis, rather than having the entire network converge at once. PVST also supports multiple spanning trees per VLAN, which provides additional redundancy and fault tolerance within a specific VLAN.

Per-VLAN Spanning Tree Protocol Plus (PVST+) is an extension of PVST that adds support for Rapid Spanning Tree Protocol (RSTP) and Multiple Spanning Tree Protocol (MSTP). PVST+ allows for faster convergence times and improved scalability, making it a popular choice for larger networks.

RSTP and PVST are two versions of STP that have been developed to provide faster convergence times, improved scalability, and better support for VLANs. While RSTP is a standard protocol that can be used on any network, PVST and PVST+ are proprietary protocols developed by Cisco and are only available on Cisco networking equipment.

Overview of Spanning Tree Protocol

The Spanning Tree Protocol (STP) is a network protocol that prevents loops in network topology by creating a loop-free logical topology. It accomplishes this by selecting a single “root bridge” and disabling all other redundant links between switches to prevent loops from forming. This process allows for reliable and redundant network connectivity without causing network instability or network failures.

The STP algorithm creates a tree-like topology, with the root bridge at the top of the tree, and all other switches and network devices branching off the root. This topology ensures that all devices on the network can communicate with one another without creating any loops, which could cause network failures or instability.

STP has evolved over time with new versions, including Rapid Spanning Tree Protocol (RSTP) and Multiple Spanning Tree Protocol (MSTP), which provide faster convergence times and greater scalability for larger networks. Additionally, some vendors have developed proprietary implementations of STP, such as Cisco’s Per-VLAN Spanning Tree Protocol (PVST) and Per-VLAN Spanning Tree Protocol Plus (PVST+).

STP is an important protocol for ensuring network stability and redundancy, and it is used in most enterprise networks to provide reliable network connectivity.

Importance of understanding the difference between RSTP and PVST

Understanding the difference between RSTP and PVST is important for network administrators and engineers because it allows them to choose the right protocol for their network’s specific needs. Here are some reasons why understanding the difference between RSTP and PVST is important:

• Network performance: Choosing the right protocol can have a significant impact on network performance. RSTP is known for its faster convergence times, which can improve network performance and reduce downtime in the event of a network change. PVST, on the other hand, provides per-VLAN spanning tree instances, which can help to reduce convergence times on a per-VLAN basis and improve network performance for certain applications.
• Scalability: The scalability of a network protocol is an important consideration for larger networks. RSTP is designed to be more scalable than STP, which makes it a better choice for larger networks with more devices. PVST+ also provides improved scalability and supports multiple spanning trees per VLAN, which can further enhance network performance and redundancy.
• Vendor compatibility: RSTP is a standard protocol that is supported by most networking vendors, while PVST+ is a proprietary protocol developed by Cisco. Understanding the differences between RSTP and PVST+ can help network administrators make informed decisions about their network equipment and ensure vendor compatibility.
• VLAN support: PVST+ provides better support for VLANs than RSTP, as it allows for per-VLAN spanning-tree instances and multiple spanning trees per VLAN. This is important for larger networks that may have many VLANs and require fine-grained control over network performance and redundancy.

Understanding the difference between RSTP and PVST+ can help network administrators make informed decisions about their network protocols and equipment, which can improve network performance, scalability, and vendor compatibility.

Understanding RSTP

Rapid Spanning Tree Protocol (RSTP) is an evolution of the original Spanning Tree Protocol (STP) that provides faster convergence times and improved network performance. RSTP works by reducing the number of states that a port can be in, from the original five states of STP down to three states: discarding, learning, and forwarding. This reduction in states allows RSTP to react to network changes more quickly, resulting in faster convergence times and improved network performance.

RSTP accomplishes faster convergence times by introducing a number of new features and optimizations, including:

• Rapid convergence: RSTP is designed to converge quickly in response to network changes, such as a link failure or a new switch being added to the network. This is achieved through faster detection times and by reducing the time that ports spend in blocking mode.
• Port roles: RSTP defines two port roles: edge ports and non-edge ports. Edge ports connect to end devices, such as servers or workstations, while non-edge ports connect to other switches or networking equipment. Edge ports are placed in forwarding mode immediately, without going through the discarding or learning states, which helps to reduce convergence times.
• BPDU processing: RSTP improves the processing of Bridge Protocol Data Units (BPDUs) by introducing a proposal-agreement mechanism. When a switch receives a BPDU that indicates a better path to the root bridge, it can send a proposal BPDU to its neighbors to inform them of the new path. If the proposal is accepted by the neighbors, the switch can immediately transition to the forwarding state.
• Link type: RSTP defines three link types: point-to-point, shared, and edge. Point-to-point links connect two switches directly, while shared links connect multiple switches through a hub or other shared medium. Edge links are connected to end devices and are treated differently by RSTP, as they are assumed to be non-participating in the spanning tree protocol.

RSTP is an important protocol for improving network performance and reducing convergence times. It is widely supported by networking vendors and is a recommended protocol for modern networks.

Understanding PVST

Per-VLAN Spanning Tree (PVST) is a Cisco proprietary implementation of the Spanning Tree Protocol (STP) that allows for multiple spanning tree instances to be created on a per-VLAN basis. PVST creates a separate spanning tree instance for each VLAN, which allows for fine-grained control over network performance and redundancy.

PVST works by creating a separate spanning tree instance for each VLAN on a switch. Each instance has its own root bridge, which allows for load balancing across multiple links and improves network performance. This also allows for improved redundancy, as a failure of a link or switch in one VLAN does not affect the other VLANs.

Some key features of PVST include:

• Per-VLAN spanning tree instances: PVST allows for a separate spanning tree instance to be created for each VLAN. This allows for fine-grained control over network performance and redundancy and allows for load balancing across multiple links.
• Rapid convergence: PVST uses the same rapid convergence mechanisms as RSTP, which allows for fast convergence times in response to network changes.
• Root bridge selection: PVST selects a separate root bridge for each VLAN, which allows for improved load balancing and redundancy.
• VLAN support: PVST supports up to 4096 VLANs, which allows for large, complex networks to be created with fine-grained control over network performance and redundancy.

PVST is a powerful tool for network administrators who require fine-grained control over network performance and redundancy. It is a Cisco proprietary protocol, which means that it is not widely supported by other networking vendors. It is widely used in Cisco networks and is an important tool for improving network performance and reliability.

Differences between RSTP and PVST

Rapid Spanning Tree Protocol (RSTP) and Per-VLAN Spanning Tree (PVST) are both implementations of the Spanning Tree Protocol (STP), but they differ in some key ways. Here are some of the main differences between RSTP and PVST:

1. Single vs. Multiple Spanning Tree Instances: RSTP creates a single spanning tree instance for the entire network, while PVST creates a separate spanning tree instance for each VLAN.
2. Convergence Time: RSTP has a faster convergence time than PVST. RSTP can converge in a matter of seconds, while PVST can take several seconds or even minutes to converge.
3. Root Bridge Selection: In RSTP, the root bridge is selected based on the lowest bridge ID, while in PVST, a separate root bridge is selected for each VLAN.
4. Port Roles: RSTP has two port roles: edge ports and non-edge ports. Edge ports are connected to end devices and immediately transition to forwarding mode, while non-edge ports transition through the discarding and learning states before entering forwarding mode. PVST does not differentiate between edge and non-edge ports.
5. Compatibility: RSTP is a standard protocol that is supported by most networking vendors, while PVST is a Cisco proprietary protocol that is only supported by Cisco equipment.
6. VLAN Support: RSTP supports VLANs but does not create separate spanning-tree instances for each VLAN. PVST supports up to 4096 VLANs and creates a separate spanning tree instance for each VLAN.

The main difference between RSTP and PVST is the way that they handle VLANs. RSTP creates a single spanning tree instance for the entire network, while PVST creates a separate spanning tree instance for each VLAN.

RSTP has faster convergence times and is a standard protocol that is widely supported, while PVST is a Cisco proprietary protocol that is only supported by Cisco equipment.

Conclusion

Understanding the differences between Rapid Spanning Tree Protocol (RSTP) and Per-VLAN Spanning Tree (PVST) is important for network administrators who want to improve network performance and redundancy.

RSTP creates a single spanning tree instance for the entire network, while PVST creates a separate spanning tree instance for each VLAN. RSTP has faster convergence times and is a standard protocol that is widely supported, while PVST is a Cisco proprietary protocol that is only supported by Cisco equipment.

By understanding the differences between these two protocols, network administrators can choose the implementation that best meets their needs and optimize their network performance and redundancy.

Reference Link

• Pluralsight Course: https://www.pluralsight.com/courses/understanding-spanning-tree-protocol. This course provides a comprehensive overview of STP, including RSTP and PVST. It covers the basics of STP, as well as advanced topics such as load balancing and root guard.

Reference Books