SIP Trunk Setup for ElevenLabs Agents

Use Voyced as an external SIP provider

This guide explains how to configure a Voyced SIP trunk in ElevenLabs Agents, allowing your AI voice assistant to place telephone calls through your existing Voyced service.

ElevenLabs supports external SIP trunks with username and password authentication for outbound calls.

For inbound calls, ElevenLabs uses direct SIP INVITE routing rather than a documented SIP registration method. Full inbound compatibility with Voyced's standard registration-based service has not been confirmed. If you set this up and it works, please let us know so we can adjust the documentation.

What You’ll Need

Before you begin, make sure you have:

• Access to your ElevenLabs dashboard

• An active ElevenLabs account with Agents enabled

• At least one configured AI voice agent

• An active Voyced telephone number

• Your Voyced SIP details:

  • Account / telephone number: Your-Voyced-DID

  • Service password: YourServicePassword

  • SIP server: sip.voyced.eu

Requirements Before You Begin

• Your Voyced account must be active.

• Your account must have sufficient calling credit and simultaneous call capacity.

• ElevenLabs must have permission to place outbound SIP calls.

• SIP authentication must use your Voyced username and service password.

• SIP signalling normally uses UDP port 5060 with Voyced.

• Telephone numbers should use full international format.

• Recommended codecs:

  • PCMA / G.711 A-law

  • PCMU / G.711 μ-law

ElevenLabs currently marks UDP transport as experimental and recommends TCP or TLS for production use.

The standard Voyced connection details use UDP. Confirm a working connection before relying on the service for production calls.

ElevenLabs does not document a SIP REGISTER option for external carrier accounts. Outbound SIP authentication does not establish inbound SIP registration.

SIP Trunk Setup Steps

1. Log in to ElevenLabs

1. Open https://elevenlabs.io

2. Log in to your ElevenLabs account.

3. Open ElevenLabs Agents.

4. Navigate to Phone Numbers.

5. Click Import number.

6. Select From SIP Trunk.

This opens the external SIP trunk configuration.

2. Enter Your Voyced Telephone Number

Under the basic configuration settings, enter:

Replace Your-Voyced-DID with your actual telephone number in E.164 format.

Example:

442012345678

The telephone number must include the country code and leading +.

Keep the number format consistent throughout ElevenLabs.

3. Configure Inbound Settings

ElevenLabs provides inbound SIP security and media options when importing a SIP trunk.

For the initial configuration, use:

These inbound authentication fields are intended to authenticate calls arriving at ElevenLabs. They are not used to register ElevenLabs with Voyced.

Do not enter your Voyced service password in the inbound authentication fields.

The recommended initial settings avoid unnecessary restrictions while testing the outbound connection.

ElevenLabs does not provide a documented SIP REGISTER configuration in this section. Inbound calls therefore require separate compatibility confirmation, explained in Step 8.

4. Configure Outbound SIP Settings

Under Outbound Settings, enter the following:

The Address field must contain only:

sip.voyced.eu

Do not enter sip: before the hostname.

UDP is provided in ElevenLabs as an experimental transport option. Use this configuration for initial compatibility testing.

Media encryption is disabled for the initial test because SRTP support has not been established for this specific connection.

Do not enable Required media encryption unless both systems support the selected method.

5. Enter Voyced Authentication Details

In the Outbound Authentication section, enter:

These credentials allow ElevenLabs to respond when Voyced challenges an outbound SIP call for authentication.

Voyced does not normally require IP whitelisting.

Keep digest authentication enabled rather than relying on source IP authentication.

An authenticated outbound SIP INVITE is different from a successful SIP REGISTER.

Whether your Voyced account accepts outbound calls without prior registration must be confirmed through a live test.

6. Save Your SIP Trunk

After entering the configuration:

1. Review your telephone number.

2. Confirm the server is sip.voyced.eu.

3. Confirm UDP is selected.

4. Confirm PCMA and PCMU are enabled.

5. Confirm your username and password are correct.

6. Click Import.

Your Voyced number should now appear in the ElevenLabs Phone Numbers section.

The number appearing in ElevenLabs confirms its configuration was saved. It does not confirm SIP registration or a successful connection to Voyced.

7. Assign Your AI Voice Agent

1. Open Phone Numbers.

2. Select your imported Voyced telephone number.

3. Click Assign Agent.

4. Select the AI voice agent you want to use.

5. Save your changes.

Example:

Make sure your AI agent is configured and ready for telephone conversations.

You should test your agent's voice, language and opening message before making external calls.

8. Configure Outbound Calling

ElevenLabs supports outbound calls using imported SIP trunk telephone numbers.

Once your Voyced details are saved:

1. Open your ElevenLabs Agents dashboard.

2. Select your configured telephone number.

3. If an outbound calling option is available, select your AI agent.

4. Enter the destination telephone number.

5. Start a test call.

Use full international format.

Example:

442012345678

The expected outbound route is:

ElevenLabs AI Agent
        |
        v
Voyced SIP Server
        |
        v
Destination Telephone

You may also start an outbound call through the official ElevenLabs API.

Example:

curl -X POST \
  "https://api.elevenlabs.io/v1/convai/sip-trunk/outbound-call" \
  -H "xi-api-key: YOUR_ELEVENLABS_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "agent_id": "YOUR_AGENT_ID",
    "agent_phone_number_id": "YOUR_PHONE_NUMBER_ID",
    "to_number": "+442012345678"
  }'

Replace the example API key, agent ID, phone number ID and destination number with your actual values.

Run this command from your own computer or application, never from a Voyced server.

If the call fails, review the SIP response and authentication information before changing the configuration.

9. Configure Inbound Calling

ElevenLabs normally receives inbound SIP calls when an external telephone provider or PBX sends SIP INVITE requests to its SIP endpoint.

The documented ElevenLabs inbound SIP server is:

sip.rtc.elevenlabs.io

For production inbound SIP delivery, ElevenLabs recommends TCP or TLS. UDP support is experimental.

This differs from Voyced's normal registration-based connection method.

Under the standard Voyced connection arrangement:

• The external telephone system registers with Voyced.

• Registration uses the Voyced telephone number and service password.

• Voyced delivers incoming calls to the registered SIP endpoint.

ElevenLabs does not currently document the SIP REGISTER functionality needed for this arrangement.

Therefore, the normal Voyced credentials entered earlier do not establish inbound call delivery.

Do not configure SIP URI forwarding as an alternative.

A full direct inbound connection requires confirmation that ElevenLabs supports registration to Voyced using the normal SIP account method.

Until this is confirmed, treat inbound calling through this direct connection as unsupported.

Testing Your Setup

Outbound Test

1. Open your ElevenLabs dashboard.

2. Select your imported Voyced number.

3. Choose your AI voice agent.

4. Place a test call to an authorised external number.

5. Check whether the call connects.

Verify:

• ElevenLabs sends the call to Voyced.

• SIP authentication succeeds.

• The destination telephone rings.

• The correct caller ID appears.

• Audio works in both directions.

• The AI voice agent responds correctly.

A successful outbound test confirms calling compatibility for the tested settings.

Inbound Test

A normal inbound test requires a confirmed SIP registration connection.

ElevenLabs does not currently document this functionality for external carrier accounts.

A successful outbound call does not confirm inbound compatibility.

Troubleshooting

Outbound Connection Fails

Check:

• SIP server is sip.voyced.eu

• Username is Your-Voyced-DID

• Password is YourServicePassword

• Transport is UDP

• Enabled codecs include PCMA and PCMU

• Voyced account is active

Confirm whether the failure is caused by authentication, unsupported transport or missing registration.

401 or 407 Error

These SIP responses indicate authentication is required.

An initial authentication challenge is normal.

If the call fails afterwards, check:

• SIP username

• Service password

• Authentication realm

• Whether ElevenLabs sends a second authenticated request

403 Error

Check:

• Account status

• Outbound calling permissions

• SIP authentication

• Caller ID authorisation

• Calling restrictions

Voyced does not normally require IP whitelisting.

404 Error

Check:

• Destination telephone number

• International number format

• SIP Request-URI

• Dialling permissions

• Which server returned the error

A 404 response does not automatically mean the destination number is incorrect.

408 Request Timeout

Check:

• SIP server hostname

• DNS resolution

• SIP transport

• Network connectivity

• UDP port 5060

ElevenLabs labels UDP experimental, so transport compatibility should be one of the first checks.

Unsupported Transport

If ElevenLabs requires TCP or TLS for your production configuration, the standard UDP connection cannot be assumed compatible.

Do not change Voyced server settings or assume alternative transports are enabled.

Confirm supported transport options before deployment.

One-Way Audio

Check:

• RTP connectivity

• SDP media addresses

• Codec negotiation

• NAT settings

• Media encryption settings

Both systems must agree on the selected codec and media transport.

Inbound Calls Do Not Arrive

Check whether the external platform supports SIP REGISTER.

The published ElevenLabs SIP trunk configuration describes inbound SIP INVITE routing rather than standard carrier registration.

Changing the AI agent assignment or telephone number label will not resolve missing SIP registration.

Final Tips

• Always use your Voyced SIP account details.

• Keep the SIP server set to sip.voyced.eu.

• Use Your-Voyced-DID as the SIP username.

• Use YourServicePassword as the SIP password.

• Voyced normally does not require IP whitelisting.

• Do not configure SIP URI forwarding.

• Never run scripts or make configuration changes on Voyced servers.

• Use PCMA and PCMU for initial audio compatibility testing.

• Treat UDP as experimental on ElevenLabs.

• Test outbound authentication before using the service.

• Do not assume inbound calls work because outbound calls succeed.

ElevenLabs provides custom SIP trunk connectivity with outbound digest authentication, but full direct compatibility with Voyced's standard SIP registration method is not currently established.

Last updated: 27/10/2026

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