SIP Connect Configuration Guide

Fonolo is compatible with all major call center platform vendors and can connect to your call center through a SIP connection over the internet.

This guide outlines the steps for setting up a SIP connection between your phone system and the Fonolo Cloud. To provide the information needed to set up the Fonolo deployment, fill out the SIP Setup Form:

Deployment configurations may vary. For more information or assistance, please email Fonolo Support, or call 1-855-366-2500. We are more than happy to help!

In-Queue Offer Message

The Fonolo call-back starts with an offer message played to the caller while they are on hold. Each queue that will be offering call-backs must have:

  • An offer message that offers the caller a call-back.
  • DTMF breakout logic that transfers the call to a Fonolo SIP extension.

The offer message must be added to your existing messaging, using any appropriate logic or wording. Optionally, we are happy to make suggestions on frequency and the threshold for activating the offer.

SIP Extension Programming

To connect to Fonolo using a SIP connection, you must configure one SIP extension per queue that will be offering call-backs. For example, if you want to offer call-backs on three queues, you need three unique SIP extensions.

You must provide:

  • A Queue Name that appears for each queue in the Fonolo Portal.
  • A Queue SIP Extension that lets Fonolo call directly into each queue and bypass the IVR.

We will provide a parallel Fonolo SIP extension for each of your Queue SIP extensions.

The Fonolo SIP extensions are automatically allocated from a unique range assigned to you. If a specific range is required, please let us know.

Your SIP extensions may need to have audio playing on them. Some phone systems will not answer a call unless it can play something to the caller. A file with a few seconds of silence will work.

SIP and Network Configurations

Fonolo uses six SIP gateways for inbound and outbound connections to your phone system. You must configure:

  • 1 or more public IP addresses that lets Fonolo reach your phone system. Load balancing or fail-over configurations are acceptable. If you are using NAT, Fonolo requires 1-to-1 NAT.
  • and as SIP peers for call transfers between your system and Fonolo. You can load balance requests between these SIP gateways.
  •,,, and as SIP peers for calls from the Fonolo system to yours. These gateways handle both the calls to the queue extension and the outbound calls to the caller.

Call Routing

Fonolo requires two call route patterns be configured:

  • One routing pattern in your dial plan that matches the inbound extension, so that Fonolo can connect to the queue directly.
  • One routing pattern in your dial plan to place outbound calls to callers. For example, Fonolo can add a 9 to the call number to route to your carrier trunk. By default, Fonolo adds a 1 as a telephone prefix, formatting outbound numbers with 11 digits.

Firewall Configurations

For Fonolo to be able to connect to your phone system, firewall rules must be configured in your system to allow the required inbound and outbound traffic:

  • Fonolo IP Block must be permitted for both inbound and outbound call traffic in your firewall.
  • The port UDP/5060 (preferred) or TCP/5060 must be permitted (inbound and outbound).
  • A UDP port range matching the media ports on your phone system inbound and UDP/10000-20000 outbound must be permitted for RTP data.


Fonolo uses the following media settings for a SIP connection:

  • g711u (μ-law), with a ptime of 20ms.
  • RFC 2833 / RFC 4733 DTMF

Fonolo Portal Setup

The Fonolo Portal is used to manage Fonolo features and view call stats. To set up the Portal, some additional information on your company and phone system must be provided:

  • The Hours of Operation for each of your phone queues that will offer call-backs.
  • Any Advanced Scheduling for holidays and other times the call center will have reduced hours or be closed.
  • The Caller ID and Phone Number that you want callers to see when they get a call-back.
  • A list of users who need access to the Portal, as well as their role within it:
PermissionStats Only UserStandard UserAccount Manager
View graphs, call logs, and real-time stats
Edit service settings×
Set up new queues and profiles×
Manage other users××

Optional Features and Procedures

While not required, there are other features or procedures that may complement your Fonolo deployment.


Fonolo supports connecting to companies via a direct site-to-site IPsec VPN. Go to Connecting via an IPSec VPN for more details.

Custom Audio Prompts and Messaging

The Fonolo service uses audio prompts that we provide in English, French, and Spanish. All prompts—for the caller or agent—are customizable using your own voice talent, letting you keep a consistent voice and terminology as your callers transition to Fonolo.

Go to the Downloads page for a spreadsheet with all the files (and suggested messaging) that Fonolo uses.

To use your own audio or voice talent, you must provide a voice file for each of the audio prompts listed in the spreadsheet that you want to use.

Audio files must be in the .wav, 16bit, 8kHz, mono PCM format.

Go to How to Upload Audio Prompts for more information on customizing the Fonolo audio.

Client First Call-back

Fonolo supports a Client First call-back approach where Estimated Wait Time (EWT) is available and can be provided from your phone system. There are 2 methods by which EWT can be provided to Fonolo:

Via a custom SIP header in a pre-agreed format

You will insert the EWT value for the appropriate queue in a custom SIP Header to be included in the opt-in transfer following call-back offer acceptance. This follows the same methodology as a pre-call question using the “SIP Header” input type.

Via an Open or Partner Web API which will allow Fonolo to request the EWT in real-time

You will provide API access to your environment including anticipated response formats for Fonolo to query the EWT value for a given queue.

The EWT you provide will be used to determine when to place a call-back to the client, at which point they will be offered an option to accept or cancel. On call-back acceptance, Fonolo will place a call to a SIP extension that routes to a priority queue to reach the next available agent as soon as possible. This priority queue should have music on hold (MOH) or other messaging configured to account for any discrepancies in agent availability.

Agent Training

It is highly recommended that you educate your call center agents about the Fonolo call-back process. The Agent’s Guide to Voice Call-Backs outlines handling a call-back and what to expect when agents receive one.

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