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3CX - SIP Trunk Guide

3CX - SIP Trunk Guide

System Preparation

Before configuring the SIP trunk it is required to go through the following checklist and make changes where necessary:

Further setup information can be found in our Academy:  3CX Academy Basic Course

3CX Version

Some providers gained support and compatibility with 3CX on a specific product version. It is advisable to always run the latest version of 3CX to ensure ongoing compatibility.

Minimum 3CX Version: 3CX Phone System 16.0

Provider Capabilities

Below is a short overview of the provider's capabilities and services and whether they’re supported or not:

  • CLNS (Clip No Screening): No
  • Catch All Routing: Yes
  • Fax in T38: Yes
  • CLIR (Number Suppression): Yes
  • DTMF via RFC 2833: Yes
  • Outbound Codec Order: G711A, G711U, G722, GSM, Opus
  • NAT Support: Yes
Configuring the Trunk with 3CX

The general instructions outlining how to add a new SIP Trunk to your 3CX installation can be found  here .

Adding the Trunk

Go to  “SIP Trunks”  and select  “Add SIP Trunk”

  • Select Country: UK
  • Select Provider in your Country: VoiceHost
  • Main trunk number: This will have been provided to you by VoiceHost. You must enter the number in the E164 number format (e.g. +44123456789)
  • Press OK

Under the  “General”  tab in the  “Authentication”  section, enter your Authentication ID and Password as well as the registrar address (these will be supplied to you by VoiceHost).

Adding Additional DIDs

To associate all other DIDs/Numbers you have in your VoiceHost account with 3CX, go to the Management Console → SIP Trunks, double-click on your VoiceHost Trunk and go to the  “DIDs”  tab

Here you should already see 1 entry; that is the Main Trunk number you have set. Add all other DIDs/Numbers you have to the list in the E164 number format (e.g. +44123456789) and press OK.

Creating Inbound Rules

Now that you have associated all your DIDs/Numbers with your SIP Trunk in 3CX, you can create Inbound Rules to set where calls will be routed when those numbers are called. Instructions on how to create Inbound Rules can be found  here .

Number Format

When configuring VoiceHost SIP Trunks in 3CX, all numbers should be entered in the E.164 number format (e.g. +44123456789), otherwise, call routing will fail.

Outbound Caller ID

VoiceHost trunks do not support Clip No Screening which means you can only present numbers that are associated with your account as Outbound Caller ID.

Outbound Rules

When configuring your Outbound Rules, numbers can be dialled in all valid number formats. More information about how to create Outbound Rules and how they work can be found here

Enabling TLS and SRTP

Under the 'General' tab please update the host to the one shown in the VoiceHost portal. This changes for TLS and SRTP so it will only be changed once enabled.
Under Options, please also upload the linked PEM under the option for the trunks 'TLS Root'.
Ensure SRTP is enabled.
Ensure TLS is set and the transport.
Ensure that host port is set to 'Auto-Detect'

Root Certificate: download here