Ever had a call suddenly drop, audio that only comes through on one side, or an IP Phone that fails to connect? Don’t worry, it’s not necessarily 3CX’s fault. It could well be that the firewall on your network isn’t configured correctly yet.

Luckily, 3CX has a Firewall Checker feature that can check whether the ports it needs are open or still blocked. The process is quick and can be run straight from the 3CX dashboard.

What Is the 3CX Firewall Checker? #

The 3CX Firewall Checker is a built-in 3CX feature that tests whether your firewall and router are allowing the connections the 3CX system needs.

If the check result is Pass, your network configuration is good to go. But if it comes back Fail, it means some port is still closed or misconfigured, and some 3CX features may not work at their best.

Why Does the Firewall Checker Matter? #

Don’t underestimate it. A misconfigured firewall can cause all sorts of problems, such as:

• Inbound or outbound calls failing.
• Audio only being heard on one side (one-way audio).
• IP Phones or softphones struggling to connect.
• Video conferencing not working properly.
• Remote extensions disconnecting frequently.

That’s why, right after installation or after replacing your router or firewall, it’s best to run the Firewall Checker first.

How to Run the 3CX Firewall Checker #

Follow the steps below.

1. Log In to the 3CX Admin Console #

Sign in to the Admin Console using an administrator account.

2. Open the Firewall Checker Menu #

Go to:

Dashboard → Firewall Checker

On this page you’ll see a button to start the check.

3. Run the Test #

Click the Run Firewall Check button.

3CX will start testing the connections and ports used for VoIP communication.

This process usually only takes a few minutes.

4. Wait for It to Finish #

Once it’s done, you’ll see one of these results:

✅ PASS

This means all the required ports are reachable and your firewall configuration is correct.

❌ FAIL

This means one or more ports are still blocked or not configured correctly.

What the Firewall Checker Results Mean #

If the Result Is PASS #

Congratulations! 🎉

It means:

• The ports are open.
• NAT is working correctly.
• 3CX is ready to use.
• The risk of call problems is much lower.

No further action is needed.

If the Result Is FAIL #

Don’t panic — the usual culprits are:

• A port hasn’t been opened on the firewall.
• Incorrect port forwarding.
• NAT isn’t configured correctly.
• The ISP is blocking a certain port.
• The router is using Double NAT.

If it fails, double-check your firewall configuration or contact your network administrator.

Tips to Keep the Firewall Checker Passing #

To keep your check results at PASS, do the following:

• Use a firewall that supports VoIP.
• Make sure the ports 3CX needs are allowed.
• Avoid using Double NAT.
• Run the Firewall Checker again after changing your network configuration.
• Use a stable internet connection.

When Should You Run the Firewall Checker? #

It’s a good idea to run the test:

• After installing 3CX.
• After replacing your router.
• After replacing your firewall.
• After switching ISPs.
• As soon as calls start having problems.
• After making any changes to your network configuration.

The sooner you check, the sooner any problem can be found.

Conclusion #

The 3CX Firewall Checker is a simple but very important feature for making sure your VoIP-based phone system runs without a hitch.

Rather than waiting for problems like choppy audio, phones failing to connect, or calls not coming through, it’s better to check things from the start. It only takes a few minutes but can save a lot of time during troubleshooting later. If the result is PASS, your network is ready to go. If it’s still FAIL, check your firewall configuration right away so every 3CX feature can work at its best.