What Causes Internet Outages?

Understanding Internet Outages

The internet has become indispensable for work, entertainment, communication, and essential services. When outages occur, they can cause significant disruptions—as seen recently with a major outage affecting Community Fibre customers in the UK on February 17, 2025. Although the exact cause wasn’t specified, the company assured customers that engineers were working to resolve the issue. This event highlights the potential impact of unexpected internet outages on daily routines.

Why Does the Internet Go Down?
How Do ISPs Prevent and Resolve Outages?
Preparing for Internet Outages
Conclusion

Why Does the Internet Go Down?

Internet outages can result from a variety of factors, ranging from minor technical glitches to major infrastructure failures. Some common causes include:

1. Network Congestion

When too many users simultaneously access and transmit data, network resources become strained—similar to trying to pour a large volume of water through a narrow straw. Peak hours often experience higher congestion. For example, cable internet connections can be more prone to congestion than fibre optic connections that offer dedicated, high-bandwidth links. Inefficient peering arrangements between ISPs can also lead to suboptimal routing.

2. Hardware Failures

The internet relies on a complex network of physical equipment—routers, modems, servers, and cables. A single failure in one of these components, such as a faulty router or a damaged cable, can interrupt connectivity. Issues like hard drive malfunctions or failures in routers and switches are common hardware-related culprits.

3. Software Bugs

Software glitches caused by coding errors, compatibility issues, or misconfigurations can disrupt the systems that manage internet traffic, leading to unexpected outages.

4. Natural Disasters

Extreme weather events such as storms, floods, and earthquakes can damage cables, power supplies, and other critical infrastructure. Floods may submerge cables, hurricanes can damage power sources, and earthquakes can sever vital connections.

5. Space Weather

Although less frequent, solar storms can release energy and charged particles that interfere with satellite communications and internet services.

6. Cyberattacks

Cyberattacks such as Distributed Denial of Service (DDoS) can overwhelm servers with traffic from botnets, effectively shutting down services for legitimate users. Similarly, Border Gateway Protocol (BGP) hijacking involves manipulating routing paths to intercept or disrupt data. With the growing reliance on cloud services, these risks are increasingly significant, underscoring the need for robust offline backups and contingency plans.

7. Outdated Equipment and Insufficient Bandwidth Plans

Even with robust ISP infrastructure, users may experience connectivity issues if they rely on outdated hardware or subscribe to plans with limited bandwidth. This becomes especially problematic during peak usage times when network demand is high.

8. Vandalism and Physical Tampering

Intentional or accidental damage to network equipment—whether due to vandalism or tampering—can disrupt service. Physical attacks on cables, servers, or other infrastructure components may lead to unexpected outages.

9. DNS Configuration Issues

Problems with DNS settings or misconfigured domain name servers can prevent proper routing of traffic, making it difficult or even impossible for users to resolve web addresses into IP addresses.

10. Scheduled Maintenance and System Upgrades

While routine maintenance is crucial for long-term stability, poorly coordinated or unexpected issues during these periods can lead to temporary outages. Planned downtime sometimes overlaps with peak usage, exacerbating the impact.

11. Human Error in Network Management

Errors in configuration, oversight, or procedural mistakes by network administrators can inadvertently cause disruptions. Even minor missteps in handling complex network systems can lead to unexpected connectivity issues.

How Do ISPs Prevent and Resolve Outages?

Redundancy: ISPs build backup infrastructure—like alternative cables and routes—to reroute traffic when a failure occurs. For instance, having multiple fiber optic cables along different paths is a common strategy.
Automatic Failover: Systems that instantly switch to backup connections help minimize downtime, sometimes even switching providers if needed.
Network Monitoring: Continuous monitoring enables early detection of issues, using advanced tools to track traffic, identify bottlenecks, and spot anomalies.
Regular Maintenance: Routine checks, firmware updates, and proactive equipment inspections reduce the likelihood of unexpected failures.
Security Measures: Robust firewalls, intrusion detection systems, and ongoing security updates are key to defending against cyberattacks.
High-Quality Equipment: Investing in reliable, up-to-date hardware further lowers the risk of outages.
Customer Support: Efficient support channels ensure users can quickly report issues and receive assistance.
SD-WAN: Software-Defined Wide Area Networking (SD-WAN) helps optimize traffic by dynamically routing data and prioritizing critical applications.

When choosing an ISP, it’s important to consider the balance between cost and reliability. More affordable services may sometimes compromise on infrastructure and maintenance, thereby increasing the risk of outages.

Preparing for Internet Outages

While ISPs work to minimize downtime, users can also prepare by taking the following steps:

Preparation Step	Description
Have backup communication methods	Ensure you have alternatives, such as a mobile phone with a data plan or a landline.
Invest in a mobile hotspot	A mobile hotspot provides internet access for multiple devices via cellular data.
Download important documents and media	Keep essential files available offline.
Set up automatic backups	Regularly back up data using cloud services or external hard drives.
Maintain essential equipment	Check that your modem, router, and other devices are functioning well.
Use offline alternatives	Download offline maps and store physical copies of critical documents.
Develop a contingency plan for work	Plan how to continue your work if your internet connection fails.
Stay informed about outages	Sign up for outage alerts from your ISP and use services like Downdetector.
Maintain an emergency kit	Keep essentials such as a portable charger and flashlight ready.

Conclusion

Internet outages can be disruptive, but understanding their causes and preparing in advance can help minimize their impact. From network congestion and hardware failures to cyberattacks and natural disasters, many factors can interrupt connectivity. While ISPs work to prevent and resolve these issues through redundancy, monitoring, and maintenance, users can further safeguard their connectivity by developing backup plans and staying informed. Together, providers and users can help ensure a more resilient and reliable internet experience.

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