What is Network Flapping? Causes, Fixes, and Explanations

What is network flapping?

Network flapping is the rapid fluctuation of network routes or interfaces between an up (active) and down (inactive) state. This constant change disturbs the network’s stability by forcing routers and switches to repeatedly calculate the best paths for data transmission. Route flapping is a specific type of network flapping in which the route information advertised by routers changes frequently within a short period.

When a network route or interface flaps, it causes a series of events:

Routing table updates: Routers continuously update their routing tables to show the current state of the network, consuming processing power and memory.
Network convergence delays: Frequent changes can slow the network’s ability to converge on a stable routing configuration, which can lead to temporary disconnections and slowdowns.
Increased network traffic: The constant updates generate additional network traffic, which can congest the network and degrade overall performance.

Understanding network flapping is crucial because it affects not just a single device but can have a cascading impact on the entire network. It can lead to decreased efficiency and increased latency and bring down network services if not addressed promptly.

What causes network flapping?

Network flapping can be annoying, and understanding its root causes is essential for effective troubleshooting. Several factors can lead to network or route flapping.

Unstable network links: These are a primary cause of network flapping. Physical connections with faults or intermittent disconnections can cause interfaces to repeatedly go up and down. In wireless or fiber-optic networks, fluctuating signal quality due to variations in signal strength can lead to instability. This intermittent connectivity forces the network to adjust constantly, resulting in route flapping.
Hardware malfunctions: Failing network devices, such as routers, switches, and network interface cards, can lead to inconsistent connectivity, resulting in route changes. Over time, aging hardware or temperature fluctuations can contribute to device instability.
Misconfigured network devices: Incorrectly configured devices may generate false signals or cause routes to oscillate. Misconfigured routing protocols, in particular, can trigger unnecessary routing updates that create instability across the network.
Software bugs and glitches: Software bugs in networking equipment or operating systems may cause routes to flap by sending incorrect status updates or failing to maintain proper routing tables. Firmware issues can also contribute to this behavior.
Environmental factors: Electromagnetic interference, power fluctuations, and physical disturbances can cause network disruptions, leading to frequent route status changes.

Each of these causes can lead to frequent and unpredictable route changes, putting additional strain on routers and making it harder for the network to stabilize.

How do these factors lead to frequent route changes?

When any of the above factors occur, they can cause a network device to frequently advertise changes in route availability:

Routing protocol reactions: Protocols detect changes and initiate updates across the network to maintain accurate routing tables.
Continuous recalculations: Routers spend excessive resources recalculating optimal paths, which can degrade performance.
Network-wide impact: Since routers share routing information, a problem in one area can affect the entire network, causing widespread instability.

How does route flapping affect your network?

Route flapping can significantly degrade network performance and reliability. When routes change frequently, network devices must constantly update their routing tables and recalculate the best paths for data transmission. This continuous adjustment leads to several adverse effects on your network.

Increased latency and packet loss

Frequent route changes cause delays in data transmission, as packets may take longer paths or get rerouted multiple times. This heightened latency affects real-time applications, such as VoIP calls, video conferencing, and online gaming. Moreover, the instability can lead to packet loss, where data packets are dropped because the network cannot deliver them efficiently.

Overloading of routing tables

Routers must process many routing updates during route flapping, which consumes excessive CPU and memory resources. Overburdened routers may become sluggish or even unresponsive, further degrading network performance. This situation can create a bottleneck affecting the router in question and the entire network segment it serves.

Network congestion

The constant exchange of routing information generates additional traffic, which competes with regular data traffic for bandwidth. This competition leads to congestion, making the network more prone to collisions and retransmissions. The increased traffic can create a ripple effect of delays and inefficiencies throughout the network.

Delayed network convergence

Routing protocols require time to settle on a stable set of routes after a change occurs. The network struggles to converge with continuous flapping, resulting in inconsistent routing information across devices. This inconsistency can cause loops or black holes in the network, where data cannot reach its intended destination, leading to service interruptions.

Security vulnerabilities

Attackers can exploit route flapping to perform man-in-the-middle attacks or inject malicious routes. The constant changes make monitoring the network for unusual activities harder, increasing the risk of security breaches. Ensuring network stability is, therefore, not only a performance issue but also a security imperative.

How can network flapping be controlled?

Addressing network flapping requires a combination of proactive measures and ongoing maintenance to ensure network stability. Here are some effective methods to control network flapping:

Implementation of route dampening techniques: Routers use these techniques to suppress routes that flap frequently. By penalizing unstable routes and gradually restoring their use as they stabilize, route dampening helps prevent them from affecting the entire network.
Regular hardware and software maintenance: Routine maintenance of network hardware (such as routers, switches, and cables) and regular updates to network device software can prevent hardware malfunctions and software bugs that may lead to flapping. Ensure that all devices are operating with the latest firmware versions to minimize the risk of bugs or vulnerabilities.
Proper network configuration and updates: Misconfigurations are a common cause of flapping, so it’s important to configure all devices properly. Regularly reviewing network settings and maintaining compatibility between devices helps prevent disruptions.
Monitoring and alerting systems: Implementing real-time monitoring and alerting systems allows network administrators to detect route flapping as it begins. Early detection means issues can be addressed before they escalate, helping maintain network stability and avoid downtime.

Each of these strategies can significantly reduce the occurrence and impact of route flapping for smoother network operations.

Best software for network router monitoring

Effective network monitoring tools are essential for identifying and controlling route flapping. Below are five top tools that can help you monitor network routers and manage flapping issues.

1. SolarWinds^® Observability (Free Trial)

SolarWinds Observability is a comprehensive monitoring software that can be deployed as a self-hosted or software as a service (SaaS) solution. It offers real-time network performance monitoring, providing detailed insights into router activity and potential issues such as route flapping. With its advanced analytics and reporting features, SolarWinds Observability allows network administrators to detect flapping early and take corrective measures. The tool’s scalability also makes it suitable for growing networks.

Key features

Real-time network performance monitoring
Customizable dashboards and reports
Early detection of route flapping

Learn more

2. ManageEngine

ManageEngine specializes in detecting and addressing route flapping. This monitoring tool provides detailed insights into your network’s routing behavior, helping you identify unstable routes quickly. ManageEngine offers easy-to-read dashboards and customizable alerts, allowing network administrators to respond promptly to network instability.

Key features

Route flapping detection and troubleshooting
In-depth network diagnostics
User-friendly interface with customizable alerts

3. Paessler PRTG

Paessler PRTG is a powerful, all-in-one monitoring solution that tracks the health and performance of network routers. PRTG supports SNMP, allowing it to gather detailed data about your network infrastructure. This enables proactive detection of route flapping and other network issues. The tool’s interactive dashboards help administrators visualize network conditions and take appropriate action.

Key features

Comprehensive router monitoring
SNMP support for detailed data collection
Interactive dashboards for real-time insights

4. New Relic

New Relic offers cloud-based observability for network routers and switches. Its instant observability features enable network administrators to monitor their infrastructure in real time. New Relic provides detailed insights into routing performance, making detecting and managing route flapping easier. With pre-built integrations, it’s easy to deploy and start monitoring quickly.

Key features

Instant observability with real-time monitoring
Prebuilt integrations for easy setup
Data-driven insights for optimizing network performance

5. LogicMonitor

LogicMonitor is a SaaS-based performance monitoring platform that excels at monitoring enterprise networks. It automatically discovers network devices and tracks their performance, helping you identify and mitigate route flapping issues. LogicMonitor’s predictive analytics and anomaly detection features allow you to prevent problems before they escalate.

Key features

Automatic discovery of network devices
Predictive analytics and anomaly detection
Customizable dashboards and reports

These tools offer a range of capabilities to help network administrators detect, troubleshoot, and resolve route flapping issues. By implementing one or more of these solutions, you can maintain better visibility over your network and ensure optimal performance.

Conclusion

Addressing route flapping is critical to maintaining a stable, efficient, and secure network. Implementing robust monitoring tools alongside proactive measures, such as route dampening and regular maintenance, can significantly reduce the impact of network disruptions. By prioritizing these strategies, network administrators can enjoy consistent performance, reduce downtime, and protect their infrastructure from potential vulnerabilities. Investing in the right tools, such as SolarWinds Observability or LogicMonitor, further enhances network reliability and minimizes the risk of route flapping in the long term.

This post was written by Chris Ebube Roland. Chris is a dedicated software engineer, technical writer, and open source evangelist. He is fascinated with the tech development world and is dedicated to learning more about programming, software engineering, and computer science. He enjoys building, playing table tennis, and sharing his knowledge with the tech community and the world at large through his articles.