Understanding The Purpose of Spanning Tree Protocol

Understanding The Purpose of Spanning Tree Protocol

IT networks for mission-critical facilities are typically complex. Redundancies are generally built into network paths to prevent service interruption should one path be blocked for some reason. Cyber security professionals often recommend these types of redundancies for business continuity. 

While these redundant paths between network segments can assist with uptime and disaster recovery, they can also cause issues with looping. Looping is when data gets caught between those redundant paths and can’t find a way out.

This switching loop (also called a bridge loop) happens due to there being more than one Layer 2 path between endpoints. The result is known as a broadcast storm. You can think of this as a “storm” of data that never stops flooding the network.

What is Spanning Tree Protocol (STP)?

Spanning Tree Protocol is designed to fix this broadcast storm problem without needing to remove the network path redundancies installed for continuity purposes. STP is a Layer 2 protocol that adds the logic needed to keep data going in the right direction.

STP is a critical technology for network controls because, without it, it would be difficult to keep necessary redundancies without experiencing problematic looping. 

Some of the key advantages of using Spanning Tree Protocol include:

  • Eliminates the broadcast storm issue
  • Increases network reliability
  • Switches flood traffic out of all ports as needed
  • Creates loop-free logical topology 

How Does STP Work?

Spanning Tree Protocol is enabled on a network bridge, and it creates a topology database of the network and applies various logic that will dictate the status of the network port.

STP directs how the switch forwards traffic when a frame arrives at the switch interface. There are five states that STP uses:

  • Disabled: Port does not participate in frame forwarding or STP operations
  • Blocking: Port does not participate in frame forwarding and discards frames received from the attached network segment
  • Listening: From the blocking state, the port transitions to the listening state
  • Learning: From the listening state, the port moves to the learning state
  • Forwarding: Port moves from learning to forwarding and starts forwarding frames across network segments

What Are the Types of Spanning Tree Protocol?

There are five types of STP that can be used.

  • STP: The original standard as defined in IEEE 802.1D
  • Per-VLAN Spanning Tree (PVST+): This enhancement by Cisco provides a separate 802.1D STP instance for each VLAN
  • Rapid Spanning Tree Protocol (RSTP): This is defined in IEEE 802.1w. It’s a faster evolution of STP
  • Rapid Per-VLAN Spanning Tree (Rapid PVST+): An enhancement by Cisco on RSTP
  • Multiple Spanning Tree Protocol (MSTP): This is defined in 802.1s and it maps multiple VLANs into the same spanning-tree instance

Advantages of Using Spanning Tree Protocol

Allows Redundancy Without Switching Loops

STP allows you to have physical network redundancies without the switching loop and broadcast storm problems. It applies a logic at the switch that “learns” what it needs to do when traffic is received and how to navigate redundant network paths.

STP is a Proven Technology

Spanning Tree Protocol has been around for decades, and is a technology that is proven to work well to avoid bridge loops. The algorithm for STP was first implemented back in 1985 by Radia Perlman.

The technology has been successfully enabling networks to automatically adjust to link failures and avoid problems when new bridges are introduced.

Wide Support for Switches & Bridges

Since the technology has been around for so long, you will find that STP is compatible with a wide variety of switches and bridges. This makes it a protocol that just about any network can implement.

Easy to Use

STP is a technology that is not difficult to implement or maintain. This makes it an easy option for facilities looking to improve network efficiency without running into expensive or time-consuming deployment.

While Spanning Tree Protocol is easy to implement, you do want to make sure that the protocol is set up correctly by a professional that understands which type of STP to use. Once an STP type is selected, that same type should be used throughout your entire network to ensure consistency and compatibility.

Compatible with Backup Systems

Spanning Tree Protocol is compatible with any network backup systems you may have that are designed for data security and business continuity. STP is an important protocol to consider for ensuring your redundant network links don’t end up causing operational problems. 

WizNucleus Provides Network Solutions That Work

Need network solutions for efficiency, optimization, and security? The WizNucleus team specializes in helping to protect mission-critical facilities and improving their networks.

Contact us today to schedule a free consultation! Call +1 (646) 558-5577 (New York, NY) or +1 (469) 481-1726 (Carrollton, TX) or reach out online.

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