3CX SBC Guide

Understanding 3CX SBCs

3CX runs in the cloud. If your client has physical desk phones in their office, a Session Border Controller (SBC) is required to securely connect those phones to the cloud 3CX system and help avoid network-related issues.

What is an SBC?

An SBC is a small device (or a phone with an SBC built in) located at the client's site. It securely connects the office desk phones to the cloud phone system and helps prevent issues such as dropped calls, no audio, or phones not ringing properly. Think of it as a security guard for the phone system, it connects desk phones to the cloud without needing to open up the firewall, while helping prevent call quality issues.

When do you need one?

If the client has desk phones in the office, that site will need an SBC.

If staff are only using the 3CX mobile or desktop app, with no physical desk phones, no SBC is needed, they connect directly to the cloud.

What are the options?

Choose the right option based on how many desk phones are at the site:

Site Size	Use This	What It Is
1-10 desk phones	Router Phone	A normal desk phone with the SBC built in, no extra hardware needed.
10-20 desk phones	SBC appliance	A small box, e.g. a Raspberry Pi or mini PC.
20+ phones / multiple networks	Server / VM	Runs as software on an on-site server or VM.
Mobile / remote workers	3CX app only	No SBC needed, connects straight to the cloud.

Limitations to keep in mind

• A Router Phone only covers up to 10 phones, larger sites need a dedicated SBC.

• One SBC per site, it can't cover multiple office locations.

• A decent internet connection is still required, a poor connection means poor call quality regardless of the SBC.

If you have any questions please contact our support team via email at [e-mail] or via phone at 1300-781-148