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SIP trunk

Vonage AI voice agents on a SIP Trunking domain

Add sip.cartesia.ai as an inbound URI on a Vonage SIP trunk, link your numbers, and assign a Cartesia agent to each one.

Start buildingRead the docs
create-provider.sh
curl -X POST "https://api.cartesia.ai/agents/phone-numbers/providers" \
  -H "X-API-Key: $CARTESIA_API_KEY" \
  -H "Cartesia-Version: 2026-08-14" \
  -H "Content-Type: application/json" \
  -d '{
    "type": "sip_trunk",
    "label": "Vonage",
    "inbound": {
      "allowed_addresses": ["216.147.0.0/18", "168.100.64.0/18"],
      "media_encryption": "allowed"
    },
    "outbound": {
      "address": "YOUR_DOMAIN.sip-us.vonage.com",
      "transport": "tls",
      "destination_country": "US",
      "credentials": { "username": "YOUR_VONAGE_USERNAME", "password": "YOUR_VONAGE_PASSWORD" }
    }
  }'

Cartesia docs: SIP trunking

What a Vonage AI voice agent can do

What teams build when they put Cartesia and Vonage together.

Your numbers and rates

Cartesia charges only agent calling rates on a SIP trunk number, and Vonage bills its own rates for the line.

Two-way calling

Inbound calls reach the agent assigned to the dialed number. Outbound calls go to your trunk's Vonage domain.

Transfers

The agent transfers calls by SIP REFER to a phone number or a SIP URI, as long as Vonage accepts the REFER.

Vonage settings

Inbound URI
sip.cartesia.ai
Inbound transport
TLS, on port 5061.
Outbound address in Cartesia
<domain>.sip-us.vonage.com, or the sip-eu or sip-ap endpoint for your region.
Outbound authentication
A user profile for digest authentication. Vonage requires a 12 to 64 character password with a digit, a lowercase and an uppercase letter.
Inbound access in Cartesia
Allowed addresses 216.147.0.0/18 and 168.100.64.0/18, Vonage's primary subnets.

Set it up

A SIP trunk: a Vonage SIP Trunking domain whose inbound URI is sip.cartesia.ai, linked to Cartesia as a provider. There is no native Vonage integration. Vendor details read in November 2026.

  1. Create a trunk in the SIP dashboard

    In the Vonage dashboard, create a SIP trunk with a unique domain name. Its outbound endpoint is that name under sip-us.vonage.com, sip-eu.vonage.com or sip-ap.vonage.com.

  2. Add Cartesia as the inbound URI

    Under Inbound Calling, pick a region, add sip.cartesia.ai as a URI, and choose TLS as the transport. Tick SRTP if you want encrypted media.

  3. Set outbound authentication and link numbers

    Create a user profile with a username and password for digest authentication. Then link your Vonage numbers to the trunk.

  4. Link the trunk in Cartesia

    Create a provider that allows Vonage's signaling subnets inbound and sends outbound calls to your trunk domain with the user profile's credentials. Import each number and assign an agent.

Documentation

Before you build

Linking moves a number

Linking a number to the trunk overrides any other domain or application the number was linked to in Vonage.

Test a transfer early

Transfers go out as SIP REFER. Place a test transfer before launch to confirm Vonage accepts it for your destination type.

Use cases for teams on Vonage

Customer support

Resolve support calls on the first try, refund and credit within your rules, and keep customers who call to cancel.

See the use case

Appointment scheduling

Book, reschedule and confirm appointments on your calendar, 24/7.

See the use case

More integrations

All integrations
SIP trunk

SIP trunking

Point your carrier at sip.cartesia.ai and run Cartesia voice agents on your own numbers, with TLS, SRTP and digest or IP access control.

  • Managed Agents
See the integration
Official

Twilio

Connect your Twilio account to bring your existing phone numbers, including international ones, to Cartesia voice agents.

  • Managed Agents
See the integration
Guide

Bandwidth

Stream Bandwidth calls to Cartesia speech to text and text to speech over WebSockets, with no audio resampling.

  • Sonic
  • Ink
See the integration

Enterprise-grade security

  • HIPAA compliant badge

    HIPAA compliant

  • SOC 2 Type 2 badge

    SOC 2 Type 2

  • GDPR badge

    GDPR

Vonage AI voice agent FAQs

How do I connect Vonage to an AI voice agent?

Over Vonage SIP Trunking. Create a trunk in the Vonage dashboard, add sip.cartesia.ai as its inbound URI with TLS, and link your numbers. Then create a provider in Cartesia that allows Vonage's subnets inbound and sends outbound calls to your trunk domain. There is no native Vonage integration.

How does Cartesia accept inbound calls from Vonage?

By address. Set the provider's allowed addresses to 216.147.0.0/18 and 168.100.64.0/18, which Vonage's support docs list as its primary subnets and recommend allowing for SIP.

What password does Vonage require for outbound calls?

A 12 to 64 character password with a digit, a lowercase and an uppercase letter. You set it on a Vonage user profile for digest authentication, then enter the same username and password as the outbound credentials in Cartesia.

Does linking a number to the trunk change its routing?

Yes. Linking a number to the SIP trunk overrides any other domain or application the number was linked to in Vonage, so its calls go to Cartesia from then on.

What does a Vonage number cost on Cartesia?

Vonage bills the line at your Vonage rates, and Cartesia adds no telephony fee on a trunk number. Agents run at $0.03/min, plus LLM usage. Numbers that Cartesia provisions, which are US only, carry a $0.014 per minute telephony fee instead.

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