Core Concepts
IP PBX
By Myroslav Orshak · operates licensed carrier infrastructure · Updated September 2026
An IP PBX is a business phone system built to run on computer networks — calls travel your office network and internet lines natively — while still being equipment (or software) you own and operate yourself.
How it works
It occupies the middle ground between eras. Like a traditional PBX, it's yours: a server or appliance in your building, under your control. Like the cloud systems, it speaks internet natively — desk phones plug into the same network as your computers, calls leave over SIP trunks, and there's no analog machinery involved.
This is also where open source lives. Asterisk and the systems built on it, FreePBX above all, let a technical team run a full-featured phone system on ordinary hardware for the cost of the server and the lines. It is the most capability per dollar in telephony, paid for with your own expertise.
Why it matters
For most businesses, the IP PBX matters as the thing they already own: 'we have an IP PBX' usually means a system modern enough to keep, connect to cheaper internet lines, and run for years more. That's a genuinely good position — no migration required, just better lines under it.
For technical teams, it's the control option: every routing rule, every integration, every byte of call data on your own hardware. The honest price of that control is operational: you become your own phone company, including on the weekend the disk fails. Teams that relish that exist; teams that discover it mid-outage also exist.
Asterisk, the open-source PBX engine underlying FreePBX and many commercial products, has powered business phone systems since 1999 — a quarter-century of production use, and the reason a capable phone system can cost nothing but hardware and expertise.
Related terms
Ready to pick a provider?
Feed your IP PBX — compare SIP trunk providers →Frequently asked questions
What's the difference between an IP PBX and a cloud PBX?
Location and ownership. Both are internet-native; the IP PBX runs on your hardware under your control, the cloud PBX runs in a provider's data center for a monthly fee. Same conversation as owning versus renting, applied to the same underlying technology.
Is an open-source PBX like FreePBX right for my business?
If someone technical owns it, it's the most capability per dollar in phones — and businesses run it happily for a decade at a stretch. Without that person, the savings convert into outages and consultant invoices. Judge the expertise honestly before judging the price tag.
What does an IP PBX need to run?
It needs a server or appliance, IP desk phones or softphone apps, and a solid office network that puts voice traffic first (QoS). It also needs SIP trunks to reach the outside world, and a firewall set up by someone who knows voice. That includes turning off SIP ALG on the router, the classic self-inflicted wound.
We already have an IP PBX — should we move to the cloud?
Not necessarily. If it's supported and does what you need, connecting it to SIP trunks is cheaper than any cloud plan and changes nothing for your staff. Revisit when the hardware ages out, the maintenance relationship ends, or you need features (deep app integration, easy multi-site) that are simpler to rent than to build.