How to Set Up a SIP Trunk in 3CX with IPComms

Introduction

3CX is one of the most popular PBX solutions available for both Windows and Linux, offering a fully-featured phone system with a modern web-based management console. Whether you are running 3CX on-premise or in the cloud, connecting it to a reliable SIP trunk provider is essential for making and receiving calls over the PSTN.

IPComms provides a straightforward SIP trunk for 3CX that supports IP-based authentication, eliminating the need for complex registration credentials. With competitive per-minute rates for US and Canada calling, high-definition audio codecs, and optional TLS/SRTP encryption, IPComms is an excellent choice for businesses using 3CX.

This guide walks you through the complete 3CX SIP trunk setup process -- from creating the trunk to configuring outbound and inbound routing, caller ID, encryption, and troubleshooting common issues.

Prerequisites

Before you begin your 3CX trunk configuration, make sure you have the following:

• 3CX Version 20 or later installed and running (Windows or Linux/Debian)
• Admin access to the 3CX Management Console
• An active IPComms account (sign up at portal.ipcomms.net)
• At least one DID (phone number) assigned to your IPComms account
• A static public IP address on your 3CX server (required for IP-based authentication)
• Firewall rules allowing UDP traffic on port 5060 (SIP) and ports 10000-20000 (RTP media)

Step 1: Create a SIP Trunk in 3CX

The first step in your 3CX SIP trunk setup is creating a new trunk in the admin console:

Log into the 3CX Management Console (typically at https://your-3cx-server:5001)

Navigate to SIP Trunks in the left sidebar

Click Add SIP Trunk

In the provider list, select Generic SIP Trunk (since IPComms is not pre-configured in the 3CX templates)

Enter a Trunk Name: IPComms

Step 2: Configure Trunk Settings

With the trunk created, configure the connection details for your 3CX trunk configuration:

Registrar/Server Settings

Authentication Settings

Since IPComms uses IP-based authentication, you do not need to enter a username or password. Your 3CX server's public IP must be whitelisted in the IPComms portal:

Codec Priority

Configure codecs in the following priority order for optimal audio quality:

Step 3: Configure Outbound Rules

Outbound rules in 3CX determine how dialed numbers are matched and routed through your SIP trunk. Navigate to Outbound Rules in the 3CX console and create the following rules:

Go to Outbound Rules in the left sidebar

Click Add to create a new outbound rule

Rule Name: US-Canada-Calling

Route: Select the IPComms trunk

Dial Pattern Rules

Add these patterns for US and Canada dialing:

Step 4: Configure Inbound Rules

Inbound rules determine how incoming calls to your DIDs are routed within 3CX. You can route calls to extensions, ring groups, IVR menus, or call queues.

Go to Inbound Rules in the left sidebar

Click Add DID Rule

Name: Main Line

DID/DDI Number: Enter your IPComms DID (e.g., 2125551234)

Trunk: Select IPComms

Set the destination for incoming calls:

• Extension -- route to a specific user
• Ring Group -- ring multiple extensions simultaneously
• IVR / Digital Receptionist -- play a menu ("Press 1 for sales...")
• Call Queue -- distribute calls among agents

Step 5: Configure Caller ID

Set your outbound Caller ID so recipients see your business phone number when you call them:

Go to SIP Trunks and edit your IPComms trunk

In the Caller ID section, set the Main Trunk No to your primary DID number (e.g., 12125551234)

For per-extension caller ID, navigate to Users, edit each extension, and set their Outbound Caller ID to a DID assigned to your account

Testing Your Configuration

After completing the 3CX trunk configuration, test both inbound and outbound calling:

Verify Trunk Status

In the 3CX Management Console, navigate to SIP Trunks. Your IPComms trunk should show a green status indicator. For IP-authenticated trunks, it may show as "Idle" rather than "Registered" -- this is normal.

Test Outbound Calls

1. Open the 3CX Web Client or pick up a provisioned desk phone
2. Dial an external number (e.g., your mobile phone)
3. Verify the call connects and audio works in both directions
4. Check that Caller ID displays your DID number on the receiving phone

Test Inbound Calls

1. From an external phone (mobile or landline), call your IPComms DID
2. Verify the call rings at your configured destination (extension, ring group, IVR)
3. Answer and confirm two-way audio quality
4. Test call features: hold, transfer, conference

TLS/SRTP Encryption Setup

For enhanced security, you can configure your SIP trunk for 3CX to use TLS for SIP signaling and SRTP for media encryption:

Enable TLS on the Trunk

3CX TLS Configuration Steps

Edit your IPComms trunk in SIP Trunks

Change the port from 5060 to 5061

In 3CX Settings, go to Network > Ports and ensure the SIP TLS port is enabled

Under the trunk's advanced settings, set the transport to TLS

Enable SRTP for media encryption

Troubleshooting

Common issues and solutions when setting up your 3CX SIP trunk setup:

Viewing SIP Logs in 3CX

To diagnose SIP-level issues:

# On Linux, view 3CX SIP logs:
tail -f /var/lib/3cxpbx/Instance1/Data/Logs/sip.log
# Filter for IPComms traffic:
grep "34.23.59.14" /var/lib/3cxpbx/Instance1/Data/Logs/sip.log
# On Windows, logs are located at:
# C:\ProgramData\3CX\Instance1\Data\Logs\sip.log