8 Spanning Tree Best Practices
The spanning tree protocol is a network protocol that helps to prevent loops in a network. Here are 8 best practices for using STP.
Spanning Tree Protocol (STP) is a Layer 2 protocol used to prevent loops in a network. It is used to ensure that there is only one active path between two nodes in a network. STP is an important protocol for network redundancy and stability.
In this article, we will discuss 8 best practices for configuring and managing STP in a network. We will also discuss how to troubleshoot STP issues and how to optimize STP performance.
1. Use Rapid Spanning Tree Protocol (RSTP)
RSTP is an evolution of the original Spanning Tree Protocol (STP) and it’s designed to reduce the time it takes for a network to converge after a topology change.
RSTP works by introducing new port roles, such as alternate ports and backup ports, which allow switches to quickly transition from blocking to forwarding states without having to wait for the entire spanning tree algorithm to complete. This reduces convergence times significantly, making RSTP much more efficient than STP.
Additionally, RSTP also supports point-to-point links, allowing you to use fewer switch ports when connecting two devices together. This can help save money on hardware costs while still providing reliable redundancy.
2. Enable PortFast on access ports
PortFast is a Cisco feature that allows access ports to transition directly from the blocking state to the forwarding state, bypassing the listening and learning states. This reduces the time it takes for an end device to become available on the network after being connected.
Enabling PortFast also helps prevent loops in the network by ensuring that only one path exists between two nodes. Without PortFast enabled, multiple paths can exist due to the spanning tree protocol’s convergence process.
By enabling PortFast on all access ports, you can ensure that your network remains stable and secure while providing faster access times for end devices.
3. Configure root bridge placement
The root bridge is the switch that all other switches in the network will use as a reference point for making forwarding decisions.
The placement of the root bridge should be carefully considered to ensure optimal performance and reliability. The best practice is to place the root bridge on the most central switch in the network, so that it can provide the shortest path between any two endpoints. This ensures that traffic flows efficiently and reduces latency. Additionally, placing the root bridge on a switch with redundant links provides additional redundancy and fault tolerance.
4. Disable STP on switch-to-switch links
When two switches are connected, STP will detect the link and block one of them to prevent loops. This is a good thing, but it also means that half of your available bandwidth is being wasted.
By disabling STP on switch-to-switch links, you can make sure that both links are active and that all of your available bandwidth is being used. This is especially important in high-traffic environments where every bit of performance counts.
5. Set the spanning tree priority to a low value for non-root switches
When a switch is elected as the root bridge, it will have the highest spanning tree priority value. This means that all other switches in the network must use this switch as their root bridge. If you set the spanning tree priority to a low value for non-root switches, then they are less likely to be chosen as the root bridge and can instead focus on forwarding traffic.
This helps ensure that your network remains stable and efficient by avoiding unnecessary changes in the topology of the network. It also reduces the risk of loops forming due to multiple root bridges being present in the network.
6. Verify that all redundant paths are active
When a network is configured with redundant paths, it’s important to make sure that all of those paths are active and working properly. If one of the paths fails or becomes blocked, then traffic can become congested on the other path, leading to slowdowns in performance.
To ensure that all redundant paths are active, you should regularly monitor your network for any changes in link status. You should also use tools like Spanning Tree Protocol (STP) to detect any loops in the network and prevent them from forming. Finally, you should configure portfast on ports connected to end devices so that they don’t cause unnecessary delays when transitioning between states.
7. Check port states and timers
When a switch is connected to another switch, it will send out BPDUs (Bridge Protocol Data Units) that contain information about the switch’s configuration. If these BPDUs are not received in a timely manner, then the port can go into an inconsistent state and cause problems with the spanning tree topology.
To prevent this from happening, you should check the port states and timers on each switch regularly. This will ensure that all ports are in the correct state and that the BPDUs are being sent and received correctly. Additionally, if there are any issues with the port states or timers, they can be quickly identified and corrected before they become a problem.
8. Monitor STP with Cisco Discovery Protocol
CDP is a Layer 2 protocol that allows network devices to share information about each other. This includes the STP configuration of the device, which can be used to detect any misconfigurations or changes in the STP topology.
By monitoring CDP messages, you can quickly identify when there are changes in the STP topology and take corrective action before it causes an outage. Additionally, CDP can also be used to monitor for rogue switches on the network, as well as verify the correct operation of redundant links.