Introduction
Desk phones are dying; they have been dying since the early 2000s, and they will likely continue to die for the next 50 years.It’s ironic that whenever people claim something is going to die soon, it inevitably takes a long time to fade away.
Despite their (uncertain?) future, many businesses continue to rely on desk phones. They remain popular because they are reliable, easy to use, cost-effective, and, most importantly, familiar to much of the workforce. For many, desk phones offer a dependable and straightforward communication tool that meets essential needs without unnecessary complexity.
The Status Quo
Our client, a school with over 100 Cisco desk phones, was faced with a dilemma: stick with an outdated CUCM system that demanded an expensive upgrade or move to a new PBX that required tossing their perfectly functional Cisco 79XX and 69XX series phones into the scrap heap.
These phones, renowned for their durability, had been workhorses for years. Replacing them would have not only been costly but also wasteful. The challenge was clear: find a modern PBX solution that worked with their existing hardware, stayed within budget, and avoided contributing to the growing e-waste crisis.
Technical Background
The school’s setup included a 30-channel PRI gateway, which bridged their CUCM (Cisco Unified Communications Manager) system to the PSTN. Fortunately, the gateway supported SIP, an open protocol widely used by modern PBX systems. This gave us an opening to bypass CUCM entirely. The tricky part? Making their phones, which relied on Cisco’s proprietary SCCP, speak SIP instead.
The Solution
The SIP Conversion
Cisco phones originally used SCCP (Skinny Client Control Protocol), but with a firmware upgrade, they can be converted to SIP. This allowed the phones to integrate seamlessly with our PBX system. The catch? Normally, the firmware upgrade and provisioning are handled by the CUCM system. Without access to CUCM, we had to get creative.
Enter TFTP
TFTP (Trivial File Transfer Protocol) is typically used to bootstrap devices like IP phones. It’s simple, lightweight, and capable of delivering the necessary configuration files and firmware updates. But here’s the downside: setting up a TFTP server, manually crafting configuration files, and uploading them for 100+ phones is a laborious process.
We needed automation.
Our solution was to use our multi-service business gateway to serve as the TFTP, DHCP, and SIP server, creating a one-stop-shop for provisioning and configuration. Here’s how it worked:
DHCP Configuration:
We configured our device to act as the DHCP server for the phones. This allowed us to control the TFTP server address the phones would use, directing them to our gateway for provisioning.TFTP Automation:
Our gateway automatically generated the required configuration files for each phone based on its MAC address. These files included SIP credentials, network settings, and any additional parameters needed to get the phones online.
This automated process meant the IT team only had to enter the MAC addresses of the phones and tick a box indicating they were Cisco devices. Our gateway handled everything else, from assigning SIP credentials to pushing it to the phones using TFTP.
The New Topology
The result was a modern, fully integrated PBX system that kept the existing phones functional and compatible without the need for CUCM.
The Outcome
The school saved thousands of dollars and kept over 100 desk phones out of the landfill. Staff now enjoy the reliability of their familiar phones, while the IT team benefits from a simplified provisioning process. Best of all, the project was delivered on time, within budget, and aligned with the school’s commitment to sustainability.
Final Thoughts
Ecosystem
Asterisk is the engine under the hood of our PBX solution. It’s powerful, open-source, and has a cult following for making Cisco phones behave. But let’s be honest—using Asterisk can feel like solving a Rubik’s Cube while blindfolded. Huge props to usecallmanager.nz for their incredible work in taming this beast (and documenting it!) and making Cisco-Asterisk integration less of a horror story.
Ingenuity is Key
Integration challenges are a given in niche markets like ours. The key is staying adaptable and thinking creatively to solve problems as they arise. Whether it’s troubleshooting unexpected quirks or navigating complex setups, we approach each challenge with a solutions-first mindset—and maybe a few cups of coffee to keep things moving smoothly.
Sustainability
At Difuse, we’re all about making tech work smarter—not just shinier. Repurposing 100+ desk phones saved money, reduced e-waste, and proved that yesterday’s hardware can handle today’s challenges. Sustainability isn’t just a buzzword; it’s how we think, work, and build. This project was a win for the environment, the budget, and our belief that great solutions don’t always mean buying new stuff. Here’s to more wins like this in the future!
