Dropped calls, choppy audio, a device that doesn’t ring—there are lots of issues that can affect VoIP phone systems. To maintain maximum uptime and perfect call quality, you need to know the basics of VoIP troubleshooting.

By knowing how to troubleshoot common Voice-over-Internet-Protocol (VoIP) issues, you can minimize the impact they have on productivity, revenue, and customer experience (CX). In turn, you can reliably enjoy the convenience and flexibility of VoIP calling.

So, how do you troubleshoot a VoIP system, and how can you prevent issues from occurring in the first first place?

How to troubleshoot common VoIP issues

The phone remains an invaluable communication tool. 54% of customers reserve phones for their most important conversations with customer service teams—and they expect impeccable call quality as they’re doing it. In fact, 42% have hung up due to background noise alone.

This proves that even minimal audio disruptions can disrupt conversation flows and lead to poor CX.

Let’s take a look at six of the most common VoIP issues that you might run into.

Poor call quality

Call quality issues like jitter, latency, broken audio, and packet loss are common, especially if you’re using free VoIP calling tools.

If there’s a time delay in the data packets being transmitted and received over your network connection, you’ll experience jitter. It causes packets between you and your customer to be sent at irregular intervals, resulting in garbled, nonsensical, or choppy audio.

Latency occurs when data packets must travel a distance between destinations, causing the entire packet to be delayed. This causes a noticeable lag in the call’s audio, making conversations frustrating.

In some cases, the VoIP connection might not be established properly, resulting in what sounds like broken audio (e.g., the speaker sounds robotic or like they’re underwater). If the VoIP packet fails to arrive at all, it causes packet loss, which can cut your calls off.

How to troubleshoot:

  • Run internet and VoIP speed tests: To maintain high-quality VoIP calls, jitter should be below 30 ms and latency below 150 ms. Run VoIP tests to confirm whether jitter and/or latency exceed acceptable speeds.
  • Clear bandwidth space: Poor call quality might be caused by insufficient bandwidth. Try upgrading your router to one that supports faster data speeds. You can also reduce bandwidth usage by reducing the number of concurrent users and removing unnecessary traffic from your local network (such as data-intensive streaming services).
  • Update quality of service (QoS) settings: Network congestion can trigger audio issues. Many routers feature QoS settings that let you prioritize VoIP packets over other types of traffic. For contact centers with high daily call volumes, this fix is often necessary to create reliably jitter-free customer experiences.

Dropped calls

Imagine you’ve been working with business data vendors and have acquired a particularly high-value lead. You jump on a call and are right in the middle of clinching a deal when—all of a sudden—the call drops.

So, you call them back, only for the call to drop again. But the next time you call them back, there’s no answer.

Losing high-value leads is the reality of what dropped calls mean for businesses. It typically affects companies that handle high volumes of outbound calls.

How to troubleshoot:

  • Check your bandwidth: Bandwidth issues can cause calls to disconnect. Try removing unnecessary bandwidth usage or upgrading your internet speeds with your internet service provider.
  • Change your UDP timeout duration via your router: If your calls are dropping after a certain amount of time, it may be that your router has UDP (User Datagram Protocol) timeouts, which means that your calls are set to automatically disconnect after a set number of minutes. Increase the UDP timeout duration via your router or switch to TCP.
  • Contact your VoIP provider: Some VoIP service providers implement UDP timeouts. If this is the case, you can contact your provider and ask them to increase the duration.
  • Update VoIP software and hardware: Make sure that all of your equipment, such as your VoIP applications, phones, routers, and firmware, is up to date.

No sound on connected calls

One-way audio can affect one or both parties, halting conversations before they’ve even begun.

How to troubleshoot:

  • Check your audio settings and connections: Is your volume turned up? Are your headsets and microphones fully connected? Always check your volume and make sure that your device is connected to the right audio output.
  • Disable SIP ALG: Some routers turn on Session Initiation Protocol (SIP) Application Layer Gateway (ALG) by default, which can lead to your data packets being blocked or misrouted. Turning off SIP ALG can fix one-way audio problems.

Phone echoing

Phone echoing describes the issue of hearing one or more voices repeated during a call. For example, you might hear your own voice being repeated back to you through the phone, or you might hear multiple voices talking over each other.

Phone echoing is distracting for the person affected and makes comprehension difficult, leading to confusion and frustration.

How to troubleshoot:

  • Turn off speakerphone: The most common cause of phone echoing is one party using a speakerphone. It can cause the caller’s voice to reverberate from the recipient’s speaker back into the microphone.
  • Check your headsets and microphones: If calls only echo when you’re using a certain headset or microphone, the equipment is most likely faulty. Purchase high-quality replacements that support VoIP business phone systems, preferably with echo cancellation.
  • Reposition VoIP hardware: Placing VoIP hardware too close together can sometimes cause electromagnetic interference, which is when two devices’ electrical fields interfere with each other. Move VoIP phones further away from your router, power strip, and other VoIP equipment to see if it helps.

Phone doesn’t ring or goes straight to voicemail when receiving inbound calls

If your phone doesn’t ring when your clients or customers call, it can have a serious impact on your reputation and revenue. It makes you appear unavailable to clients, harming your reputation as well as retention and loyalty. Plus, you can miss out on profitable opportunities.

How to troubleshoot:

  • Check your Do Not Disturb and call forwarding settings: Make sure that the VoIP phone isn’t in DND mode and that your call forwarding isn’t accidentally set to direct calls to a different device, user, or voicemail inbox.
  • Check your work hours: If you notice that inbound calls are being sent straight to voicemail at certain times of the day, it could be because your phone’s work hours aren’t the same as your business schedule. Check and change your work hours in your online portal.
  • Make sure your phone is still registered: Your VoIP phone may have been unregistered by mistake. Contact your VoIP provider to have your devices re-registered.

Unable to make outbound calls

Not being able to make outgoing calls is a productivity killer for sales, customer support, and pretty much any team that relies on effective communication. Whether your call won’t connect or you’re seeing an “X” on your device’s screen when you’re trying to make a call, there are a couple of easy fixes.

How to troubleshoot:

  • Disable SIP ALG: Once again, SIP ALG is a likely cause. It might be disrupting VoIP network traffic and routing calls to the wrong IP address. Try disabling it to see if it fixes the problem or switch to a VLAN (virtual local area network).
  • Update and restart the device: It might sound simple, but updating your software and restarting your VoIP device can sometimes fix this common issue.

How to prevent VoIP issues

Now, let’s take a look at some general VoIP troubleshooting tips and preventative tactics.

Proactively ensure network stability

A virtual phone system setup relies on peak network performance to avoid call issues like audio delays, broken audio, and dropped/disconnected calls.

To support high-quality VoIP calls, you should:

  • Ensure that you have sufficient bandwidth speeds of at least 80-100 kbps per concurrent call.
  • Purchase a business-grade router that’s capable of handling VoIP traffic.
  • Configure your QoS settings to prioritize VoIP calls.
  • Use ethernet cables and wired connections for desk phones where possible.

Perform regular device management

In addition to purchasing compatible VoIP hardware and software, you should perform regular updates and evaluations. This ensures that vulnerabilities are patched and your hardware/software is equipped with performance-optimizing features.

Don’t forget to routinely check that your router and VoIP devices are properly configured and that all of your cable connections are fully inserted and damage-free.

Choose a reputable VoIP provider

The best way to avoid VoIP quality issues and downtime is to choose a reputable VoIP provider that meets your business’s calling needs, such as VoIP for small business phone solutions.

This allows you to access benefits that optimize uptime and audio quality, such as redundancy, VoIP call quality tests, and round-the-clock support.

Crucially, you should choose a provider with a proven track record of delivering 99.999% uptime SLA. This essentially means that even if parts of the network fail, businesses can reliably continue communications without interruptions.

Key takeaways

VoIP troubleshooting may take some trial and error, but the faster you recognize the problem, the quicker you can resolve it to mitigate the business impact.

Different VoIP issues will require different troubleshooting steps, but many involve checking your bandwidth usage and internet speeds, re-configuring your router settings, and adjusting QoS settings to prioritize VoIP traffic.

Remember to purchase high-quality VoIP devices, software, and equipment and assess them regularly to ensure they’re up-to-date, connected, and free from damage.

FAQs

How do you troubleshoot a VoIP system?

VoIP problems can come from three main sources: your internet connection, your hardware, and the VoIP service itself. Troubleshooting should involve checking all three. To start with, check your internet speed and the stability of your connection. Then, check your headphones and microphone are working. If both of these elements are fine, use your VoIP provider’s knowledge base to diagnose and fix the issue.

What do you need to ensure you have stable VoIP service?

Firstly, you need sufficient bandwidth and a strong internet connection. You need at least 100 Kbps/call. Then, you need a reliable service provider. Compare service level agreements (SLA) and their expected uptime. Ideally, you want a solution with the ‘five nines’, which is 99.999% uptime. There should also be high levels of security to prevent downtime caused by external factors.

Updated Jun 25, 2025