Set up a SIP trunk

SIP trunks can be created and managed using the Infobip web interface and API. For background on trunk types, codecs, and billing plans, see What is SIP trunking.

The following diagram shows what source IPs and destination IPs mean for a static SIP trunk:

If a static SIP trunk definition does not include at least one source IP, then SIP traffic cannot be sent from your equipment to the Infobip infrastructure. Similarly, if a SIP trunk definition does not include at least one destination IP or FQDN, then incoming voice traffic to the Infobip platform cannot be forwarded over your SIP trunk.

For registered SIP trunks, make sure that your Private Branch Exchange (PBX) is compatible with registered trunks.

Before you start

By default, a single Infobip account can have:

• Up to 10 trunks per account.
• Up to 10 trunks per Infobip data center.
• Up to 3 IP addresses per trunk for inbound traffic.
• Up to 3 IP addresses per trunk for outbound traffic.
• SIP trunks in up to 2 different Infobip data centers.

For US-based SIP trunks, register service addresses before creating the trunk. See Managing service addresses.

Using the Infobip web interface

SIP trunks are managed from the Infobip web interface.

Go to Channels and Numbers > Channels > Voice and WebRTC > SIP Trunking.

If you intend to create a trunk in one of the Infobip USA data centers, or if your Place of Primary Use (PPU) is in the United States, make sure that you declared a service address first (see Service addresses).

Choose the SIP trunk provider

Select CREATE SIP TRUNK and choose the type of trunk (trunk provider) you wish to provision. See Supported SIP trunk types and characteristics for more information.

For SIP trunks others than Infobip (that is, Freshworks, Genesys PureCloud, and so on), see Specific notes for provider trunks.

Choose plan and options

Choose between a Metered or Unlimited channel plan. For more information about these channel plans, see SIP trunk channels and related billing plans.

Select the number of required channels.

Main trunk settings

Follow the wizard to complete the SIP trunk details. Depending on the SIP trunk provider (INFOBIP, FRESHWORKS, and so on) and type (registered, static), the following fields may need to be completed:

Infobip SBC locations

When you create a SIP trunk, Infobip returns the SBC address(es) you need to configure on your environment. The format depends on whether your account already has existing SIP trunks:

• If you had no existing SIP trunks in your account on April 13, 2026 (first trunk ever created): you receive a unique FQDN for each trunk you create, along with a list of IP subnets to allowlist on your firewall.
• If you already had one or more SIP trunks in your account on April 13, 2026: you continue to receive static SBC IP addresses, including for any new trunks you create.

You can check whether you have existing SIP trunks in the SIP trunking section of your Infobip account.

SBC addresses for accounts with existing SIP trunks

The following table lists the SBC IP addresses by data center.

SBC addresses for new accounts (FQDN-based)

When you create your first SIP trunk, the system generates a unique FQDN for that trunk. The FQDN follows this format:

{unique-id}.{region}.sip.voice.infobip.com

For example: a1b2c3d4-e5f6-7890-abcd-ef1234567890.eu.sip.voice.infobip.com

The FQDN is returned at trunk creation and is specific to that trunk. Each trunk gets its own FQDN.

In addition, you must allowlist the returned IP subnets on your infrastructure to allow traffic from the Infobip SBCs.

IP configuration

This configuration step appears only when configuring an INFOBIP static trunk.

Enter the list of source and destination IP addresses/FQDNs.

For destination IPs, if you do not have multiple redundant network elements, simply add your static IP, with the default SIP port of 5060. If you enter more than a single IP/FQDN, you can select the routing strategy to be applied:

• Failover: When sending calls to your SIP equipment, destination IPs are selected in the order they are configured. If the first IP is unavailable, the next IP is selected, and so on.
• Round robin: When sending calls to your SIP equipment, destination IPs are selected in sequential order and distributed evenly. Round robin is best used with symmetrical trunks (that is, trunks with the same capacity).

For source IPs, specify all the IP addresses from which your equipment sends traffic to the Infobip network. These can be different from the destination IPs.

Review order

Review all settings, then go on with the confirmation of the trunk creation. You can go back to previous steps if you wish to change any value.

When you select Pay now, your creation request is submitted to the Infobip system and a dialog displays the Infobip primary and backup SBC IP addresses (see SIP trunking redundancy). Safelist the Infobip SBC IP addresses on your infrastructure so that traffic can be processed on both sides. For registered trunks, this dialog also includes your username and password.

After you acknowledge this dialog, you are brought back to your list of SIP trunks. Monitor the Admin and Action status. See SIP trunk status.

Retrieving your authentication (registered trunks)

For registered trunks, the final dialog during trunk creation displays your username and password. If you lose your credentials or suspect they are compromised, reset them. From your SIP trunk list, select your registered trunk and select the Reset password button. A dialog displays both the username and a new password.

Using API

For more information about the API methods used for managing locations and SIP trunks, see Calls API platform (opens in a new tab).

Specific notes for provider trunks

The following information is relevant to the specific provider trunks only.

Freshworks trunks

Freshworks provider trunks enable you to use Freshworks services (call center Freshcaller (opens in a new tab)) while leveraging Infobip as the underlying voice connectivity provider for both inbound and outbound calls.

Freshcaller uses Twilio as its communication engine. To use Infobip for voice connectivity with Freshcaller, you must:

• Configure a Bring Your Own Carrier (BYOC) connection with Twilio
• Have a properly configured Freshworks account

Follow the official Freshworks documentation (opens in a new tab) for setup instructions.

To set up an Infobip provider trunk for Freshworks, you must provide these two specific parameters:

When defining multiple Freshworks trunks in the same Infobip data center, consider the following specific behaviors:

• Channels
  • On inbound traffic (origination): The channel count defined per SIP trunk is applied as a channel upper limit on each individual trunk.
  • On outbound traffic (termination): The total channel count for all defined Freshworks trunks is applied as an upper group limit across all Freshworks trunks.
• Reports and Logs
  • On inbound traffic (origination): Reports and logs show the SIP trunk ID and SIP trunk name used for sending traffic to Freshworks.
  • On outbound traffic (termination): Reports and logs show the ID and name of the oldest provisioned Freshworks trunk. This is because traffic from Freshworks does not include a trunk identifier.

Genesys PureCloud trunks

See the Genesys PureCloud Provider SIP Trunk Configuration Guide (opens in a new tab) to help you set up a Genesys PureCloud trunk and configure it in Genesys PureCloud.

You can determine the appropriate region where the SIP trunk needs to be created based on your Genesys PureCloud web interface login URL:

Cisco Webex trunks

See the Cisco Webex Provider SIP Trunk Configuration Guide (opens in a new tab) to help you set up a Cisco Webex trunk and perform the Cisco Webex BYOC Enterprise configuration.

OpenAI Realtime SIP trunks

To connect Infobip voice to the OpenAI Realtime API over SIP, provide your OpenAI Project ID.

Connect inbound caller to your AI agent

Use Infobip Call Routing to connect inbound callers to your OpenAI Realtime project.

To set this up, follow these steps:

1. Create a new route in Call Routing and set your OpenAI trunk as the destination.
2. Configure the route based on how users will call your agent:
   • PHONE: Ensure you have at least one Infobip DID. For detailed steps, see Call Routing documentation.
   • WHATSAPP: Make sure you have at least one WhatsApp sender enabled for WhatsApp Voice. The setup is similar to phone, but inbound configuration is done from the WhatsApp Voice tab of your sender in the Numbers application on the web interface.
   • WEBRTC: See the filter-based route execution documentation. In summary:
     • Your WebRTC client (using the Infobip WebRTC JS or mobile SDK) must place an applicationCall to CALL_ROUTING.
     • Your route in Call Routing must have a filter criteria defined of type WEBRTC.

Enable your AI agent to call recipients

Outbound calls from OpenAI to Infobip over the SIP trunk are not supported directly. To enable your AI agent to call recipients, build a voice application using the Calls API platform.

This application:

• Creates the outbound call to the recipient(s), either as an individual call (opens in a new tab) or bulk calls (opens in a new tab).
• When the call is answered, connect it to an outbound SIP call to your AI agent by:
  • Using the create Dialog (opens in a new tab) method.
  • Setting the childCallRequest to use the SIP endpoint type and referencing the OpenAI trunk sipTrunkId.

Understanding SIP trunk status

A SIP trunk has three independent status classes (Administrative, Registration, and Action) that together describe its lifecycle. Use the following table to interpret each status value reported in the Infobip web interface or returned by the SIP trunking API (opens in a new tab).

Next steps

After you create a SIP trunk, use Call Routing to forward inbound calls received on Infobip numbers to your telephony equipment over the trunk.