# Configuring SIPTRUNK Register Authentication Trunk
Before proceeding with trunk configuration, ensure that you have purchased at least one DID on the [SIPTRUNK ](https://www.siptrunk.com)platform.
***
### SIPTRUNK Setup Guide
To enable inbound calling, you must first complete the required configuration on the SIPTRUNK platform.
1. Sign in to your [SIPTRUNK ](https://login.siptrunk.com/)account.
2. Your SIP trunk will also need to be configured via the customer portal. You must implement the following whitelisting requirements detailed in the article [Interconnecting with SIPTRUNK](https://support.siptrunk.com/hc/en-us/articles/38762945316379).
Once completed, continue with the trunk configuration in PortSIP PBX.
***
### Configure a Register-Based Trunk in PortSIP PBX
A **SIPTRUNK Registration Trunk** corresponds to a **Register-Based Trunk** in **PortSIP PBX**.
You can configure a Register-Based Trunk at **either** of the following levels:
* **System Administrator level**\
The trunk can be **shared with one or more tenants**.
* **Tenant Administrator level**\
The trunk can be used **only by the tenant** who created it.
***
### Create a Register-Based Trunk
#### Step 1: Open the Trunks Page
1. Sign in to the PortSIP PBX Web Portal as a **System Administrator** or **Tenant Administrator**.
2. From the left navigation menu, go to **Call Manager > Trunks**.
3. Click **Add**, then select **Register Based Trunk**.
***
#### Step 2: Enter Basic Trunk Information
Configure the following fields:
* **Name**\
Enter a friendly name for the trunk.
* **Brand**\
Select **SIPTRUNK**.
* **DID Pool** *(Tenant Admin level only)*\
If you are configuring this Register-Based Trunk at the **Tenant Admin level**, you must define the **SIPTRUNK DID numbers** for this trunk.
The tenant can:
* Use **only** the DID numbers defined in the **DID Pool**
* Create **inbound and outbound routing rules** using those DID numbers
* Configure **outbound caller IDs** for extensions using those DID numbers
The DID Pool can include a **single number**, **multiple numbers**, or **number ranges**, separated by **semicolons**. For example:
```
16468097065
16468097065-16468097066
16468097065-16468097066;16468097069
16468097065-16468097066;16468097070-16468097080
```
Click **Next** to continue.
***
#### Step 3: Configure Trunk Credentials
Enter the registration credentials provided by CM.com:
* **Authentication Name**\
Enter the **SIPTRUNK username** configured on the **SIPTRUNK** platform\
(for example: `portsipuser`).
* **Password**\
Enter the **SIP trunk password** obtained from the CM.com platform.
Click **Next** to continue.
***
#### Step 4: Configure Trunk Options
* **Max Concurrent Calls**\
Set the maximum number of simultaneous calls that PortSIP PBX can establish using this trunk.
> ❗**Recommendation**\
> Keep the default values for other options unless you have specific requirements.
Click **Next** to continue.
***
#### Step 5: Assign the Trunk to Tenants *(System Administrator level only)*
This step is available **only** when configuring the Register-Based Trunk at the **System Administrator level**.
1. Assign the trunk to one or more **tenants**.
2. Define the **DID Pool(DID numbers)** for each tenant. Separated by **semicolons**.
> ❗**Important**
>
> * A DID can be assigned to **only one tenant**
> * Each tenant can use **only the DID numbers** within its assigned DID Pool
**DID Pool examples:**
```
16468097065
16468097065;16468097066
16468097065-16468097066;16468097069
16468097065-16468097066;16468097070-16468097080
```
***
#### Step 6: Save the Configuration
Click **OK** to save the settings. The trunk configuration is now complete.
***
### Expected Result
* PortSIP PBX successfully registers the trunk with the **CM.com** platform.
* On the **Trunks** page, the trunk status is displayed as **Online**.
***
> ❗**Note**\
> Ensure that your **SIPTRUNK** SIP credentials are correct and that outbound network access from the PBX is allowed.
Now you can follow the article to [Configuring inbound and outbound calls](/portsip-communications-solution/configuring-sip-trunks/siptrunk-sip-trunk/configuring-outbound-and-inbound-calls.md).
---
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