Back to Blog
Tech

Different IP Addresses for Failover

Published on:

December 5, 2014

Failover capabilities are essential for ensuring uninterrupted service in PBX installations, especially with the growing use of high-bandwidth wireless connections like 4G. PBX systems traditionally use LAN-based IP addresses, but dynamically switching to a public IP address during failover has posed challenges. To address this, we've introduced a new feature - the PBX periodically probes a specified URL to detect its public IP address and adjusts the routing table accordingly. This feature simplifies the process, eliminating the need for complex scripts and allowing systems to automatically switch to the correct IP during failover, ensuring continuous operation. The feature will be available in version 5.2.5.

Christian Stredicke

Failover is an important feature for most PBX installations. With the availability of high-bandwidth wireless like 4G, it becomes more and more popular to use the wireless connection when the primary landline internet access becomes unavailable.

For a long time, we've made it possible for the PBX to run in the LAN, which replaced the local IP address with publicly routable IP addresses. The IP replacement list was already a topic of many forum discussions.

When it comes to dynamically switching the presented IP address in the case of a failover, however, we were in trouble. In theory, it'd be possible to run a script that tests for the public IP address and then uses the REST interface and changes the routing table. Not everyone is a bash wizard, however, and it would even require different scripts for the different operating systems.

This was the reason why we went ahead and added a new feature that takes the URL for probing the public IP address of the PBX and an interval time value. The PBX will then periodically download the URL and set the public IP address of the PBX accordingly. The public IP address can be referenced with the magic name “public” in the routing list, like this:

192.168.0.0/255.255.0.0/192.168.1.1 0.0.0.0/0.0.0.0/public

Then the PBX would present 192.168.1.1 in the LAN and whatever-is-the-public-address in all other cases.

In the response from the web server, the PBX expects an IP address in human readable format, or in JSON-format, where the object must contain a entry called “ip” (for example, see http://myjsonip.appspot.com/). It's possible to use public servers, but obviously you can also use your own servers.

The failover will obviously take some time. The polling interval determines how fast the change is being detected. Obviously there's a tradeoff between polling (too) often and the time it takes to reflect the new address.

The new settings will be available right under the replacement list in 5.2.5.

Latest Articles

View All
Editorial

Sonic: Music on Hold and the Vodia PBX

Music on Hold plays an important role in how callers experience wait times and perceive service quality. With Vodia PBX Version 70, we’ve enhanced Music on Hold to deliver neutral, calming, high-quality audio that reassures callers while they wait. These improvements, combined with flexible streaming options, emergency messaging, and full support for cloud and on-premises multi-tenant environments, help businesses reduce dropped calls and create a more positive caller experience before an agent ever answers.

February 17, 2026
Editorial

Open Source PBX vs Commercial PBX: What You’re Really Managing

Organizations often start with an open source PBX for flexibility, but as systems move from initial setup to daily operations, the real cost becomes management, maintenance, and long-term reliability. This article explores the difference between building a PBX stack from frameworks and running a commercial, integrated PBX platform, focusing on operational complexity, security responsibility, upgrades, and ongoing maintenance. It explains how a purpose-built PBX shifts the burden from continuous engineering to stable operation, helping teams prioritize clarity, control, and scalability as requirements grow.

February 12, 2026
Announcement

The Vodia PBX and Google Gemini

Vodia PBX now integrates Google Gemini with JavaScript IVR and Voice Agents, enabling real-time, AI-driven call handling and intelligent routing. By combining Gemini’s multimodal large language models with Vodia’s programmable IVR framework, organizations can build voice agents that stream audio in real time, make routing decisions through function calls, and handle both basic and attended transfers with AI-assisted screening. This integration allows businesses to automate call flows, reduce hold times, and improve productivity using conversational AI that works directly inside the PBX.

February 4, 2026