Connecting an External Extension to 3CX PhoneSystem is often requested, and can be extremely useful for linking small remote offices and home workers. Here we get a shot at using other phones as External Extensions.

Using …

Correct Router Configuration is a key element in ensuring correct communications between 3CX PhoneSystem and external entities such as external extensions, VoIP Provider services, and other Bridged PBXs.
NAT and/or PAT
When a network host A sends …

This document will provide an overview of the more common concepts which need to be kept in mind when configuring 3CX PhoneSystem inside your network infrastructure, including the following topics:

NAT Configuration
STUN Resolution
DNS Resolution in a …

As seen in Part 1 of this article, STUN enables a SIP entity running behind a NAT to discover its public IP and what type of NAT is running on the gateway it is connected …

STUN stands for Simple Traversal of User Datagram Protocol (UDP) through Network Address Translators (NAT’s). Typically it is used in several different network implementations and scenarios, one of which is in VoIP implementations. Because of …

How and when can I switch off STUN Resolution
STUN resolution is necessary for the PBX to understand what it’s public IP Address is, and what port mappings are in effect for Media (to attempt NAT …