Posts in Year 2026

SETTING UP AN INTERNAL PHONE SYSTEM WITH OLD CISCO® IP PHONES AND ASTERISK

In 2020, I wrote a post on updating firmware on old Cisco® IP phones, and I got carried away by other projects and this project went on the backburner. This year I decided to complete this project, so that I could use these wired VOIP phones as an internal phone system across multiple rooms, where I could dial a number and speak to a person in a different room. I use this to interact with my family members when I want to ask them something and do not want to walk over for whatever reason.

Asterisk is an open source PBX - Private Branch Exchange software that I used to set this up. The process is a bit involved and is tricky to get right if you miss something in the configuration.

I will describe the process in detail in this post. Note that this post does not describe a setup for making outbound calls or receiving inbound calls on actual landline phone numbers. This is for creating a custom extension per phone, and calling those extensions, similar to what you find in hotels, where you can call one room to another by dialing that room’s number.