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VoIP – Troubleshooting Guide

PT

This guide helps you to fix the most common issues related to VoIP. Please follow the steps below before contacting support.

1. Types of Problems

Problems related to VoIP can appear in different ways.

🌐 Connection Issues

📵 Phone has no connection or is turned off
⚠️ “Not Registered” or “Offline” message
🔑 Unable to authenticate in the system

📞 Call Issues

⛔ Unable to make calls
📥 Unable to receive calls
❌ Calls fail or do not complete

🎧 Quality Issues

🔇 No sound (one-way or both ways)
🔁 Echo during the call
⏱️ Delays (latency)
✂️ Voice cuts or interruptions
🎚️ Poor audio quality

2. Checks to Perform

Checks should be carried out in the order indicated, testing the service after each step.

Before You Start

    • Does the issue occur on only one device or multiple devices?
    • Does the issue affect all calls or only some?
    • Is the problem constant or intermittent?
    • Did the issue start after any change (network, equipment, or location)?

Check Device Status

☎️ IP Phones

    • Confirm the device is powered on
    • Check the display for errors (e.g., “No Service”, “Not Registered”)
    • Ensure the network cable is properly connected

💻📞 Softphones

    • Confirm the application is open
    • Check that the user is logged in
    • Ensure there are no connection errors

Check Network Connection

    • Verify connection to the network (Ethernet or Wi‑Fi)
    • Confirm internet access (open web pages)
    • Test another device on the same network

Restart Equipment

    • Restart the IP phone (power off/on)
    • Restart the computer (if using a softphone)
    • Restart the switch/router (if applicable)

Check VoIP Registration

    • Confirm the device status is “Registered”
    • If there is an error:
      • Review login credentials
      • Sign in again
      • Validate VoIP server configuration

Audio Check

If there is a sound issue:

    • Check the device volume
    • Verify microphone and speakers
    • Test with a headset
    • Check audio settings in the system

Assess Connection Quality

Quality issues may indicate network problems:

    • High latency (delay)
    • Packet loss (audio cuts)
    • Jitter (variation in transmission)

Check Local Network and Infrastructure

    • Confirm the device is connected to the correct network
    • Check for network congestion
    • Verify VLAN configuration (if applicable)
    • Avoid public or unauthorized networks

Cross‑Testing

To isolate the issue:

    • Test another IP phone
    • Test another softphone
    • Test in a different location
    • Make both internal and external calls

Advanced Checks (if applicable)

    • Verify firewall or network blocks
    • Confirm required VoIP ports are open
    • Validate QoS (Quality of Service) configuration

3. Best Practices

The following best practices aim to ensure efficient, secure, and continuous use of the services. Applying them helps prevent issues, improve performance, and simplify troubleshooting when problems occur.

Network

    • Prefer a wired connection instead of Wi‑Fi
    • Avoid congested networks
    • Ensure a strong signal (when using Wi‑Fi)

Equipment

    • Restart devices regularly
    • Keep firmware and software up to date
    • Use high-quality audio equipment

Usage

    • Avoid downloads or streaming during calls
    • Monitor connection quality
    • Use only configurations approved by Iscte

3. User Support

If the issue persists after completing all checks, you should contact IT Support.

Quick Checklist

Before contacting Support, confirm:

    • 🔌 Equipment is powered on and functioning
    • 📡 Device is registered in the system
    • 🌐 Network connection is active
    • 🌐 Internet access is working
    • 🔁 Equipment restarted
    • 🎧 Audio checked (microphone/speakers)
    • 🔄 Tested with another device
    • 🧭 Issue is not widespread

Information to Provide

To ensure faster and more effective analysis, always include the following information in your request:

Context

    • Location
    • VoIP number/extension
    • Device type (IP phone or softphone)
    • Type of problem (e.g., no audio, registration failure, poor quality)

Problem Details

    • Detailed description of the problem
    • When the issue started
    • Whether it affects other users
    • Whether it occurred after any change

Tests Performed

    • List of troubleshooting steps already performed

Evidence

    • Screenshots/Photos
    • Error messages
    • Observed behavior

Support Channels

Example Requests

Example 1

VoIP Extension: 223456

Location: Building 1, Room 1W02

Date Reported: May 21, 2026

My VoIP phone (extension 223456) has been unavailable since yesterday.

The device display shows the message “Not Registered”, and I am unable to make or receive calls.

Troubleshooting Steps Performed:

        • Verified the network connection (cable is properly connected)
        • Restarted the IP phone
        • Tested another device on the same network outlet (working correctly)

The issue persists. Please check the configuration or the service associated with this extension.

Example 2

VoIP Extension: 229999

Location: Building 2, Office D214

I am experiencing call quality issues with the VoIP extension mentioned above.
During calls, there are frequent audio dropouts, delays, and difficulty maintaining a consistent conversation. The issue occurs on both internal and external calls.

Troubleshooting Steps Performed:

        • Restarted the IP phone
        • Confirmed wired network connection
        • Tested with another VoIP device on the same network outlet (same issue)
        • Verified that there was no heavy network usage at the time

The issue persists consistently. Please analyze the network quality or the VoIP service configuration associated with this extension.

FAQ