# Connect 3CX with a SIP trunk

> Register your 3CX phone system to the PBX with a SIP trunk so it can make and receive calls.

- URL: https://kb.voipcloud.online/au/teams-and-sip/sip-trunking/3cx/
- Section: Microsoft Teams and SIP trunking › SIP trunking
- Type: guide
- Applies to: All countries
- Last reviewed: 2026-11-09

This guide connects a 3CX phone system to your PBX with a SIP trunk. 3CX signs in to the PBX with a username and password, then makes and receives calls through your phone numbers.

## Before you start

- Order a trunk licence and channels: go to **Services** › **SIP trunking**, set the number of **Channels** (one per simultaneous call), click **Add licence**, tick **Agree to service terms and conditions** and click **Submit order**.
- Have admin access to your 3CX system.

## 1. Create the SIP trunk in the PBX

1. Go to the **PBX** tab. Drag **SIP trunk** from the **Accept, make and divert calls** group onto the canvas and click the gear icon.
2. Enter a **Name** and set the **Number of channels**.
3. For **Mode**, choose **SIP registration**.
4. Choose a **SIP trunk call plan**. Without one, outgoing calls won't work.
5. Choose the **Caller ID** for outgoing calls, or **Keep originator's caller ID** to use the number 3CX sends.
6. Click **Save**.
7. Connect an [Inbound number](https://kb.voipcloud.online/au/pbx/receive-calls/inbound-number/) with the numbers that should ring on 3CX to the SIP trunk.
8. Click **Apply configuration**.

Open the trunk's settings again and note the **SIP credentials**: **Domain**, **Username** and **Password**. The **Domain** is shown as server and port, separated by a colon. Also note the **Transport protocol**: TCP, or TLS if **TLS encryption** is turned on in **Settings** › **General**. See [SIP trunk](https://kb.voipcloud.online/au/pbx/accept-make-divert/sip-trunk/) for every setting.

## 2. Add a 3CX system

**Note:** Menus can change between versions. If a label is different, check the vendor's own help.

Skip this if your 3CX system is already running.

1. Sign in to your 3CX account and click **Add System**.
2. Choose a plan and click **Next**, then follow the setup. The options depend on the 3CX product you choose.

![Your 3CX systems page with the Add System button](https://kb.voipcloud.online/au/images/teams-and-sip/sip-trunking/3cx-add-system.webp)

## 3. Add the trunk in 3CX

1. When installation finishes, sign in to the 3CX **Admin Console**.
2. Go to **Admin** › **Voice & Chat** and click **Add Trunk**.

   ![3CX Voice & Chat page with the Add Trunk button](https://kb.voipcloud.online/au/images/teams-and-sip/sip-trunking/3cx-add-trunk.webp)

3. For **Country**, choose **Generic**. For **Trunk**, choose **Generic VoIP Provider**.
4. Fill in the fields from the PBX trunk's SIP credentials:

 | 3CX field | Enter |
 | --- | --- |
 | **Name** | Any name for the trunk. |
 | **Main Trunk Number** | Your main phone number. |
 | **Registrar/Server** | The **Domain**, without the colon and port. |
 | **Port** (next to Registrar/Server) | The port after the colon in the **Domain**. |
 | **Authentication ID (SIP User ID)** | The **Username**. |
 | **Authentication password** | The **Password**. |

5. Check the details and click **Save**.

![3CX Add Trunk page with the Generic VoIP Provider fields](https://kb.voipcloud.online/au/images/teams-and-sip/sip-trunking/3cx-trunk-settings.webp)

If your 3CX version has a transport setting for the trunk, set it to match the trunk's **Transport protocol** in the PBX (TCP, or TLS).

## 4. Add inbound and outbound rules in 3CX

- Add an inbound rule for each phone number you send to the trunk, so incoming calls reach the right 3CX extension or queue.
- Add an outbound rule that sends calls out through the new trunk.

## Check it works

1. In 3CX, the trunk's status turns green under **Voice & Chat**. In the PBX, the SIP trunk's **Status** shows **Online**.

   ![3CX Voice & Chat list with the new trunk showing a green status](https://kb.voipcloud.online/au/images/teams-and-sip/sip-trunking/3cx-trunk-status.webp)

2. Call one of your numbers from a mobile. A 3CX extension should ring.
3. Call a mobile from a 3CX extension. The mobile should show your caller ID.

If calls fail, check the inbound and outbound rules in 3CX first. If the trunk stays offline, check the username and password: after failed sign-in attempts, the PBX blocks the IP address for 5 minutes. You can check this with **Check IP address for blocking** in the trunk's settings.

## Next steps

- [SIP trunk](https://kb.voipcloud.online/au/pbx/accept-make-divert/sip-trunk/): inbound and outbound rules for numbers and extensions hosted on 3CX.
- [Device offline](https://kb.voipcloud.online/au/troubleshooting/device-offline/) if the trunk won't register.