How to Solve Network Connectivity Problems (And Prevent Them)

Why Network Connectivity Issues Are So Frustrating

Network connectivity problems take on many forms. Complete loss of internet connection. Slow network performance. Intermittent outages. Random dropped connections. That situation where one computer connects just fine and another can't connect to the network at all.

And network connectivity issues can have any number of root causes: faulty hardware, configuration changes or problems, outages from your ISP. Or maybe something as simple as an unseated cable (something as simple as having your ethernet cable run over by a rolling chair can result in hours of troubleshooting).

It's the lack of visibility into the actual cause and the complexity of modern networks that makes connectivity problems so difficult to troubleshoot. There are so many potential points of failure.

A single network is composed of many network devices (routers, switches, access points, firewalls). Each one of these can have hardware and configuration issues. Wireless networks add even more complexity with their own connectivity issues (weak signal, interference) as well as DHCP, DNS, IP address conflicts, and more.

Common Causes of Network Connectivity Problems

The first step to troubleshooting and fixing network connectivity problems is understanding what commonly causes connectivity issues. Here are the most common causes of connectivity problems and what makes each cause problematic.

1. Hardware Failures and Physical Connections

Network connectivity problems can be caused by physical hardware failures. Network routers, switches, network interface cards, and even Ethernet cables wear out over time and get damaged (sat on, crimped around a corner, chewed on by a curious puppy). Physical faults like these cause intermittent connectivity that are often challenging to pinpoint. Loose or damaged connections to switch ports or router interfaces cause intermittent packet loss that is nearly impossible to detect without extensive packet captures.

2. ISP and External Network Issues

Occasionally, the problem is outside of your network. Internet connectivity issues might be caused by congestion on your Internet service provider's network, issues with routing, or problems with their hardware and infrastructure. Run a traceroute to your destination and see where your packet loss begins. If the packet loss is past your gateway, the problem is with someone else.

3. DNS and IP Configuration Problems

DNS (domain name system) issues prevent your device from resolving domain names to IP addresses. It appears that you have no internet connection when your network is working fine. IP address conflicts are when two network devices use the same IP address, which causes connectivity issues for both devices. Problems with your DHCP server can result in devices not getting a valid IP address.

4. Firewall and Security Settings

Security settings such as overly restrictive firewall rules can also create connectivity problems by blocking legitimate network traffic. These connectivity issues appear mysterious until you review firewall logs to see which legitimate traffic was being blocked. VPNs can sometimes disrupt normal network traffic. Incorrect VPN settings will also cause problems and even experienced network admins can get tripped up.

5. Wi-Fi Signal Strength and Interference

Wireless network problems can also occur from poor signal strength or interference from other Wi-Fi networks operating on the same frequency. Outdated router firmware doesn't help either. Access points positioned too far from users or blocked by physical obstacles create dead zones and unreliable connections.

How to Troubleshoot Network Connectivity Problems

When troubleshooting network connectivity problems, it is essential to be systematic in your approach. Don't jump from place to place trying every troubleshooting step without first verifying the issue exists.
Begin at the bottom of the OSI model and work your way up to avoid spending hours on diagnostics and configuration when the problem was something simple.

Step 1: Check Physical Connections and Power

Verify the physical connections are plugged in and powered on. These are called basics for a reason.

Check that your modem and router have power. Make sure all Ethernet cables are firmly seated. Look for damaged cables or loose connections. If you have indicator lights on your network devices, verify they show normal operation.

For wireless connectivity problems, verify the Wi-Fi is enabled on your device and that you are not in airplane mode. Verify that you are connected to the correct Wi-Fi network. Ensure that the signal strength is sufficient for a reliable connection.

Step 2: Restart Your Devices

The classic "turn it off and back on again" approach works because it clears temporary glitches and resets network states. Restart your computer first, then your modem and router.

When restarting network equipment, wait 60 seconds after powering down. This fully clears the device caches. Power on your modem first and wait for it to fully initialize before turning on your router. This ensures proper synchronization with your ISP.

Step 3: Test with a Direct, Wired Connection

Test if your problem is on the wireless network or on the wired network. Connect a single computer directly to your modem with an Ethernet cable. Ignore your router and wireless network entirely.

If the problem goes away, then the issue is with your router or wireless access point. If it doesn't, then your modem, Internet connection, or device are suspect. This troubleshooting step of methodical isolation is essential for quickly troubleshooting network problems.

Don't spend 30 minutes configuring and troubleshooting your router if the problem is with your ISP.

Step 4: Use Network Diagnostics Tools

Command-line tools provide useful diagnostics that point to the actual cause of a network connectivity problem. Open a command prompt (Windows) or terminal (Mac/Linux) and run the following:

Tool	What It Does	How to Use It	What to Look For
Ping Test	Verifies local network connectivity and tests internet connectivity	Ping your router's IP address (typically 192.168.1.1 or 192.168.0.1). Then ping an external IP address like 8.8.8.8 (Google's DNS).	If you can ping the IP address but not domain names, you have a DNS problem. Learn more about using ping for troubleshooting.
ipconfig/ifconfig	Checks your IP configuration	Check your IP configuration to make sure your device has a valid IP address (whether you use dynamic or static IP addresses), subnet mask, and default gateway.	An IP address starting with 169.254 indicates DHCP failure.
Traceroute	Identifies where packets are being dropped	Use traceroute (or tracert on Windows) to see each hop between your device and the destination.	You can see whether the problem is on your local network, your ISP's network, or beyond.

Step 5: Check DNS Server Settings

If you can connect to websites using IP addresses but not with domain names, you likely have DNS resolution problems. Try switching to public DNS servers like Google DNS (8.8.8.8 and 8.8.4.4) or Cloudflare DNS (1.1.1.1).

In Windows, you can flush your DNS cache using the command prompt: run ipconfig /flushdns to clear cached DNS entries that might be causing problems.

Step 6: Verify Network Settings and Configuration

Review your computer's network adapter settings (Device Manager in Windows or Network Preferences in macOS) to ensure the network adapter is enabled and drivers are up to date. Check for IP address conflicts by reviewing the IP configuration of other devices on your network. Ensure the DHCP server (usually the router) is properly configured to assign IP addresses.

Troubleshoot Common Network Problems with Advanced Tools

If basic troubleshooting steps have not solved the problem, advanced tools like network monitoring software can help dig deeper into the root cause.

Analyze Network Traffic and Bandwidth

Network congestion can cause connectivity issues that are intermittent and difficult to diagnose. Network monitoring software like our own Paessler PRTG Network Monitor constantly tracks bandwidth utilization on all your network devices. Network monitoring software will help you spot congestion before it causes service interruptions. High bandwidth utilization by specific devices or applications can also slow down the entire network.

Packet loss is a symptom of a problem and the percent of lost packets is a vital metric to watch. Even a small percentage of packet loss can have a major impact on real-time applications like VoIP and video conferencing. Understanding what causes packet loss helps you decide whether the issue is related to network hardware, configuration, or network congestion.

Check for Firmware and Driver Updates

Outdated router firmware and network adapter drivers can cause connectivity problems, security vulnerabilities, and performance degradation. Check your router manufacturer's support website for firmware updates and apply them during a maintenance window. Update your network adapter drivers on each of your computers and networked devices to ensure compatibility and performance.

Review your Firewall and Security Settings

Firewall rules and security settings that are too restrictive can block legitimate network traffic, causing connectivity problems. Review your firewall configuration to ensure that necessary ports and services are open for your applications. Check firewall logs to see if legitimate traffic is being blocked or dropped. Firewall logs are the first place to look for blocked packets when troubleshooting connectivity issues.

Tips for Preventing Network Connectivity Problems

Most connectivity issues can be prevented through proactive monitoring and maintenance. This helps you identify developing problems and address them before they affect your users.

Implement Proactive Network Monitoring

Instead of waiting for users to report problems, proactive network monitoring automatically detects connectivity issues before they cause service outages.

PRTG Network Monitor continuously monitors all your devices for availability, bandwidth utilization, packet loss, and other vital network performance metrics. Automated alerts notify you of problems the moment devices become unreachable or key thresholds are exceeded.

Historical data from PRTG and customizable dashboards give you instant visibility into network health. With PRTG, there is no more guessing during troubleshooting or frantic firefighting when network problems arise. You can proactively address problems before they impact users.

Maintain Accurate Network Documentation

Keep clear documentation of your network topology, IP address assignments, and change management. Accurate network documentation is invaluable during troubleshooting to help you quickly see what changed. Documented troubleshooting procedures for past issues will also allow you to quickly repeat the successful steps to troubleshoot in the future.

Regularly Scheduled Maintenance and Updates

Schedule regular maintenance windows to apply firmware updates, security patches, and configuration reviews. Test redundant internet connections and failover systems to verify they work in an outage. Perform preventive maintenance by replacing aging network equipment before it fails.

Monitor for Early Warning Signs

Look for connectivity issues and performance that is getting gradually worse. Slow increases in latency, gradual loss of bandwidth, intermittent errors that temporarily resolve themselves are often early warning signs of an issue that will ultimately result in a service outage.

Network monitoring solutions like PRTG watch all these metrics over time, providing historical data for trend analysis and proactive problem identification.

When to Contact Your IT Support Team or ISP

There are some network connectivity problems you have to defer to outside support to solve. When to call your internet service provider and when to escalate to your internal IT support team.

Contact your Internet service provider (ISP) if you've verified the issue exists with a direct, wired connection to your modem. If you can't get multiple devices to connect to the network or if you are seeing consistent packet loss beyond your network gateway, call your ISP. The technicians can verify your line quality and test for outages in your area. They can verify your modem is operating correctly.

Escalate to your internal IT support team when problems are affecting multiple users, when you believe the problem is with the network infrastructure, or when troubleshooting tasks are above your area of expertise or time is limited. Network connectivity problems in enterprise environments may also indicate the need for an network infrastructure upgrade or a more robust monitoring solution.

Conclusion: Take Control of Network Connectivity Issues

Network connectivity problems can be much less painful to troubleshoot and fix if you approach them systematically. Check the physical layer and basic network connectivity first before jumping into more complex diagnostics and network device configuration.

Isolate and identify the real cause of the problem before jumping to solutions. Test in a logical manner with a direct connection to eliminate wireless or router issues as possible causes. Use simple and reliable diagnostics such as ping and traceroute to validate local network connectivity and find points of packet loss.

Prevent problems before they occur. Proactive network monitoring with real-time device monitoring and automated alerts will allow you to detect issues before they affect users. Keeping current documentation of your network and performing regular maintenance and upgrades will save time troubleshooting connectivity issues that could have been prevented.

Need to take control of network connectivity problems? Learn more about PRTG, check out the 30-day free trial and how it can help you maintain reliable network connectivity across your entire infrastructure.