Set up SIP trunk

This guide walks you through configuring an Elastic SIP Trunk for both inbound calls (customers call your AI agent) and outbound calls (your AI agent calls customers).

Prerequisites

Before you begin, ensure that you have:

• An active SIP trunk account.
• A phone number that supports SIP Trunking.

Understand the setup

Both inbound and outbound calls are supported through Elastic SIP Trunk, but each direction requires different configuration in your SIP trunk and in Agora Console. The table below summarizes the key differences.

Basic setup

The following steps are required for both inbound and outbound calling.

Verify your SIP trunk phone number

To confirm your phone number is ready for SIP trunk configuration:

1. Log in to Twilio Console.
2. Navigate to Phone Numbers → Manage → Active Numbers.
3. Check that the number you want to use is active and supports SIP Trunking.
4. If you do not have a number, select Buy a number and choose a number from the list.

Create or select an Elastic SIP Trunk

To set up a trunk that handles inbound and outbound calls:

1. Go to Elastic SIP Trunking → Manage → Trunks in Twilio Console.

2. Select Create a new SIP Trunk (or select an existing one).

3. Give it a descriptive name. For example, Production Trunk.

   

Assign the phone number to the Elastic SIP Trunk

To link your phone number with the SIP trunk:

1. Go to Phone Numbers → Manage → Active Numbers.
2. Select the phone number.
3. Under Voice Calling settings, set the number to use your Elastic SIP Trunk.
4. Save changes.

Check secure trunking setting

To determine which transport protocol to use when you import your number:

1. Open SIP Trunk → General Settings.

2. Locate Secure Trunking.

3. Check whether it is enabled or disabled:

   • Enabled: Choose TLS for the Transport Protocol.
   • Disabled: Choose TCP or UDP for the Transport Protocol.

4. Save any changes.

   

Outbound calling setup

Complete the following steps to enable your agent to make outbound calls through your SIP trunk phone number.

Configure the Termination URI

To set up the domain that Agora will use to reach your SIP trunk:

1. In your SIP trunk, go to Termination.

2. Set a custom Termination SIP URI. For example: yourcompany.pstn.twilio.com.

3. This domain is required later as the SIP Trunk Address when you import the number.

   

Create an IP Access Control List (Whitelist)

Without correct IP whitelisting, your SIP trunk blocks Agora traffic. To allow Agora's traffic through Twilio, create an Access Control List (ACL) containing the Agora SIP outgoing IPs for your phone number's country code:

To create the ACL:

1. Go to Elastic SIP Trunking → Manage → IP Access Control Lists.

2. Select + Create new Access Control List.

3. Give your ACL a descriptive name.

4. Add the Agora SIP outgoing IPs for your country code, listed above.

5. Save the Access Control List.

   

   

Add IP Access Control List

1. In your SIP trunk, go to Termination → Authentication.

2. Under IP Access Control Lists, select the authentication list you just created. If you do not see the list you created, access it by selecting View all Authentication lists.

3. Select Save.

   

   

Credential Lists (Optional)

You can create username and password authentication if required.

• If you do not specify a credential list, you can leave the SIP Trunk Username and SIP Trunk Password fields blank when you import the number.
• If you configure a credential list, you must specify the same username and password in the SIP Trunk Username and SIP Trunk Password fields when you import the number.

To set up a credential list:

1. Under Authentication, find Credential Lists.
2. Use the + button to create a new list.
3. Give your list a descriptive name.
4. Specify a username and password.
5. Select Save.

Import the outbound number

Once your SIP trunk is configured, import the number. See Import a phone number for step-by-step instructions. Use your Termination URI as the SIP Trunk Address and match the Transport Protocol to your Secure Trunking setting.

Inbound calling setup

Complete the following steps to enable customers to call your agent through your SIP trunk phone number.

Configure Origination URI

1. In your SIP trunk, go to Origination.

2. Select Add new Origination URI.

3. Enter the Agora SIP Origination URI for your region:

   The Origination URI depends on the country code of your phone number. Select the URI for your region and enter it in your SIP trunk.

   • United States

     Transport	URI
     TLS	sip:sbc-us-west-1.viblinx.com:5061
     TCP/UDP	sip:sbc-us-west-1.viblinx.com:5060

     Supported country codes: +1 (United States)

   • Americas, Europe, Oceania, and Brazil

     Transport	URI
     TLS	sip:sbc-sa-east-1.viblinx.com:5061
     TCP/UDP	sip:sbc-sa-east-1.viblinx.com:5060

     Supported country codes: +52 (Mexico), +54 (Argentina), +55 (Brazil), +56 (Chile), +51 (Peru), +44 (United Kingdom), +33 (France), +49 (Germany), +39 (Italy), +34 (Spain), +61 (Australia), +64 (New Zealand)

   • Asia-Pacific, India, and Africa

     Transport	URI
     TLS	sip:sbc-ap-south.viblinx.com:5061
     TCP/UDP	sip:sbc-ap-south.viblinx.com:5060

     Supported country codes: +82 (South Korea), +65 (Singapore), +81 (Japan), +91 (India), +886 (Taiwan), +27 (South Africa), +20 (Egypt), +254 (Kenya)

4. Set Priority to 10 and Weight to 10 (default).

5. Select Add.

Configure number routing

1. Go to Phone Numbers → Manage → Active numbers.
2. Select the number you want to use for inbound calling.
3. Under Voice Configuration → Configure with, select SIP Trunk.
4. Choose the trunk you created in Basic setup.
5. Select Save configuration.

Import the inbound number

Once SIP trunk origination and routing is configured, import the number and associate it with an agent to answer inbound calls. See Handle inbound calls for step-by-step instructions.

Configuration checklist

Before testing inbound and outbound calls, make sure you address each item in the checklist:

Troubleshooting

If you encounter issues with your SIP trunk setup, use the following table to identify and resolve common problems.

Next steps

• Import a phone number: Import your configured SIP trunk number
• Set up a campaign: Use your imported number to create an outbound calling campaign
• Handle inbound calls: Associate a number with an agent to answer inbound calls
• Publish your agent: Publish an agent to use with your imported number