Common VoIP Problems and Their Solutions

VoIP (Voice over Internet Protocol) phone systems provide businesses with a cost-effective and feature-rich alternative to traditional landline systems. However, VoIP systems can develop issues that affect call quality and reliability.

In this guide, we’ll explore the most frequent VoIP problems businesses face and provide actionable solutions to resolve them.

Choppy Audio and Dropped Calls

Nothing frustrates callers more than choppy audio or dropped calls. If your VoIP system exhibits either of these issues, there are a few likely culprits to investigate.

Internet Connection Issues: VoIP calls travel over the internet, so an unstable or slow internet connection will degrade audio quality. Try upgrading your internet plan to boost bandwidth if needed. Also check for sources of interference like microwaves or cordless phones that operate on the 2.4 GHz band.

If using Wi-Fi, optimize your wireless network. Switch to 5 GHz if available or move closer to your router. A wired ethernet connection is ideal for VoIP phones whenever feasible.

Exceeding Bandwidth Limits: Ensure your internet plan provides enough upload and download bandwidth to support your concurrent calls. As a rule of thumb, each VoIP call requires at least 90-100 kbps symmetrical bandwidth. Exceeding available bandwidth causes lag, jitter, and call drops.

Quality of Service (QoS) Not Configured: Quality of Service (QoS) settings prioritize VoIP traffic on your network so calls get through even when bandwidth is scarce. Check your router and switches support QoS, and that it’s enabled with proper prioritization policies.

Faulty VoIP Phones: Defective hardware like worn network cards, dirty contacts, or malfunctioning microphones can affect individual VoIP phones. Swap affected phones to determine if the issue follows the device. Regular maintenance and replacing aging phones helps minimize problems.

Ports Not Correctly Configured: Your VoIP system may not have critical ports like SIP and RTP properly configured. Your VoIP provider can verify ports are correctly forwarded and open. Using a business-class router or firewall optimizes port configuration for VoIP.

Echo on Phone Calls

Frustrating echo on your phone calls? Here are some potential ways to remedy the situation:

Impedance Mismatch: Impedance mismatch between your VoIP phone and the telephone circuit can cause echo. Use a VoIP adapter to match impedance and reduce echo. Analog telephone adapters (ATAs) designed for VoIP can improve impedance better than generic adapters.

Suboptimal VoIP Gateway: Your VoIP gateway connects your system to the PSTN (public switched telephone network). Low-quality, improperly configured or overloaded gateways can induce echo. Upgrading to an enterprise-grade VoIP gateway may help significantly.

Incorrect VoIP Phone Settings: Check your VoIP phone settings including microphone gain, which should be around 50%. Also disable “handsfree” mode which can cause echo issues. Adjust volume to moderate levels to prevent audio feedback.

Network Latency Problems: High network latency due to insufficient internet bandwidth or QoS misconfiguration can induce echo. Boost your bandwidth and double check QoS settings as covered earlier in this article.

Nearby Speakers Causing Feedback: Speakers in close proximity to VoIP phones can cause audio feedback. Keep phones away from speakers and noise sources to prevent reverberation. Also use noise-cancelling handsets whenever feasible.

Difficulty Making Outbound Calls

Outbound calls failing? Start troubleshooting with these tips:

Account Registration Issues: Ensure your VoIP accounts are properly registered to your provider’s servers. Log into your VoIP provider portal to check registration status. Re-register accounts if needed.

DID Number Configuration: Your DIDs (direct inward dial numbers) must be correctly assigned to accounts and devices. Audit DID mapping in your VoIP control panel, making corrections as needed.

Port Blocking: Your firewall settings may be blocking the ports your VoIP system requires for outbound calls. Work with your VoIP provider to identify required ports and verify firewall access.

Calling Restrictions: Some providers enforce calling restrictions for high-risk numbers like tolls or international. Check your account doesn’t have limits for your intended call destinations.

Insufficient Credits/Funds: Prepaid accounts or accounts with capped usage may have insufficient funds to place calls. Check your balance and add funds when running low. Automate payments via credit card to avoid interruptions.

Number Blacklisting: Your VoIP numbers may end up blacklisted if detected making spam calls. Request number removal from spam registries. Beware cheap numbers often end up blacklisted.

Poor Inbound Call Quality

Frustrated callers? Inbound call issues usually point to telephony circuit problems:

Telecom Circuit Connection: Physical PSTN connections feeding your VoIP gateway can degrade. Alert your telephony provider to inspect connections. Consider a backup or bonded circuit for redundancy.

Telecom Circuit Bandwidth: Narrowband PSTN circuits only support a fixed number of concurrent calls. See if your circuits offer any bandwidth upgrades to improve call capacity.

Telecom Circuit Noise & Distortion: Telephone circuit noise disrupts VoIP call quality. Your carrier may need to troubleshoot and resolve any line noise or distortion issues present.

Ground Loop Noise: Differing building ground potentials induce troublesome ground loop noise over PSTN lines. Install isolation transformers to break the ground loop and remediate noise.

Difficulty Transferring Calls

Call transfer enables moving a call to another number or extension. If transfers fail, try these tips:

Dial Plan Misconfiguration: Your dial plan establishes how calls route and transfer in your VoIP system. Audit your dial plan settings and fix any syntax errors preventing proper call transfers.

Codec Mismatch: The codecs on both sides of a call transfer must match to hand off the call cleanly. Standardize codecs systemwide and reconfigure if needed.

Firewall Blocking Signaling: Aggressive firewalls may block key VoIP signaling like SIP needed to transfer calls. Follow your VoIP provider’s recommendations to ensure your firewall permits signaling.

Extension Unreachable: The transfer destination extension must be registered and active to receive calls. Check the extension is online and re-register if needed before transferring calls.

Insufficient User Permissions: Users may lack the call transfer feature permission in your VoIP system. Reassess your user roles and grant transfer abilities to those needing them.

Distorted Audio

Choppy “robotic” sounding audio? Try these tips to clean up call quality:

Conflicting Codecs: When each end selects a different codec, you end up with an incompatible codec mismatch. Standardize your codec selection systemwide. G.711 provides optimal call clarity.

Overloaded Processor: Many concurrent calls can overload your VoIP gateway processor. Upgrade to a more powerful model, or install multiple gateways to split the load.

Congested Network: Excessive latency, jitter and packet loss from a congested local or WAN network disrupts VoIP audio. Optimize your network infrastructure and bandwidth as detailed earlier.

VoIP VLAN Misconfiguration: Your VoIP traffic should be segregated onto a dedicated VLAN. This prevents competing traffic from degrading quality. Verify your VLANs and QoS settings are correct.

One-Way Audio

One-way audio means one caller can’t hear the other. Usually this points to a firewall or NAT issue:

Firewall Blocking Audio: More than just signaling, your firewall also needs to permit RTP media streams too. Work with your VoIP provider to identify required ports.

NAT Causing Media Disruption: Network address translation (NAT) commonly disrupts VoIP media streams. Enable SIP ALG or install a media gateway to traverse NAT. A public IP address avoids NAT issues.

RTCP Not Enabled: RTCP provides important feedback on RTP media streams. Ensure RTCP is active end-to-end so either party can report and resolve one-way audio.

No Audio At One Site

Can one site hear the other but not vice versa? Troubleshoot with these tips:

Local Firewall Blocking Audio: Double check the local firewall at the site with no audio permits the required RTP media streams. Work with your VoIP provider to pinpoint open ports needed.

Defective Local Phone Hardware: Try swapping the affected VoIP phone with a known good device. Failing hardware often manifests as isolated audio problems.

QoS Misconfigured: The site with no audio may not be prioritizing VoIP traffic correctly. Verify QoS is active and properly granting VoIP the highest priority.

Power Over Ethernet (PoE) Issue: VoIP phones often use PoE for power. Failures can knock phones offline. Troubleshoot PoE injectors and switches. Also try a different wall jack.

Intermittent Audio Problems

Random choppy audio or robotic voice? This points to network packet loss.

Wi-Fi Interference: Nearby equipment generating RF noise in the 2.4GHz or 5GHz Wi-Fi bands causes intermittent packet loss. Identify and relocate sources of interference like microwaves.

Network Congestion: When network bandwidth is maxed out, VoIP traffic gets dropped, disrupting call quality. Upgrade bandwidth and implement QoS to prevent congestion issues.

Packet Loss on Circuit: WAN connectivity problems like high latency, jitter, and packet loss severely degrade VoIP call quality. Engage your ISP to troubleshoot and correct packet loss on your circuit.

Packet Loss on LAN: Faulty network gear like flaky switches or cables cause packet loss on your LAN. Inspect each node and cable thoroughly and replace any suspect equipment.

Bad VoIP Phones: Some phones with weak Wi-Fi or faulty ethernet adapters exhibit intermittent connection losses. Swap affected phones to help isolate the issue.

No Caller ID

Caller ID not working? Try these tips:

Caller ID Disabled: Some VoIP providers require you explicitly enable caller ID. Log into your configuration panel and ensure caller ID is active.

Number Not Provisioned: Your DIDs need proper caller ID data assigned in your VoIP provider’s configuration. Make sure your numbers are provisioned for caller ID as needed.

Wrong Codec Negotiated: Some voice codecs don’t support caller ID data. Make sure caller and receiver agree on a compatible codec like G.711 that delivers caller ID.

Blocked by Originating Carrier: The caller’s carrier may block sending caller ID for privacy reasons. There’s nothing you can do to receive blocked caller ID.

SIP Headers Stripped: Some VoIP gateways inappropriately strip SIP header info like caller ID. Replace with a model that fully supports SIP signaling.

Call Quality Differs by Location

If call quality issues seem isolated to certain sites, focus troubleshooting there:

Insufficient Local Bandwidth: Remote sites may need their internet circuits upgraded to properly handle VoIP traffic needs.

Poor Local Wi-Fi Coverage: Choppy Wi-Fi at remote sites causes quality problems on wireless phones. Perform a Wi-Fi survey and add access points to improve coverage.

Onsite Hardware Issues: Isolated issues point to local problems like failing routers, switches, or faulty VoIP phones. Inspect each component at sites with quality complaints.

Latency & Jitter Problems: Excessive latency and jitter on the local internet connection degrades call quality. Engage the local ISP to troubleshoot circuit issues.

QoS Not Configured Properly: The remote site may not be prioritizing VoIP traffic correctly. Ensure QoS is active and tuned to prefer voice traffic.

Finding the Right VoIP Provider

While VoIP issues can be frustrating, a reliable business VoIP provider can minimize problems dramatically. The key is finding a robust, business-focused VoIP phone system designed for optimal call quality.

Check out our list of reliable and secure VoIP providers—we cover everything you need to know to choose the right solution for your business.