Connecting 3CX Phone Systems (Bridges)
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You can connect two separate 3CX Systems together, allowing you to make calls between branch offices for free just by utilizing your existing internet connection. A “Bridge” can be assigned a prefix, which you will dial to access the other 3CX Phone System. This prefix must be followed by the extension number you wish to reach on the other 3CX Phone System.
Alternatively, you can assign the extensions in one Office to start with one number (e.g. 100, 101, 102 where all extensions start with 1), and the extensions in the second Office to start with a different number (e.g. 200, 201, 202 where all extensions start with 2). This way, users from one office can directly dial the extension number without using a prefix making calling between offices or branches seamless. In this case, when the outbound rule is created, you must ensure that the prefix corresponds to the numbering plan selected and that no digits are stripped.
Creating a Bridge
A bridge must be either a “Master” or a “Slave.” First you create a Master bridge on one 3CX, and then you create a Slave bridge on the other 3CX.
Step 1: Create a Bridge on the Master Phone System
- In the 3CX Management Console go to “Bridges” node and click “Add > Master Bridge.”
- Enter a name for the bridge and take note of the virtual extension number. (You will need this number when you create the “Slave” Bridge connection so ensure that the virtual extension number generated is not in use on the other 3CX System which will host the “Slave” bridge endpoint.)
- Specify an “Outbound rule prefix” to be used for this bridge. If you specify 6, then you must dial 6100 to reach extension 100 on the other 3CX Phone System. You can also dial 600 to reach extension 600. This prefix is also used to redial missed calls between offices.
- Specify the maximum number of simultaneous calls you want to allow through this bridge.
- Specify the Authentication password that will be used for “ Authentication” by the slave bridge.
- The “Remote PBX uses SBC/Tunnel Connection” option allows all SIP and RTP traffic to be sent via a single TCP port using the 3CX Tunnel. If enabled, enter the public IP address or FQDN of the “Slave” 3CX Phone System, for example “office2.3cx.com.” Then specify the remote 3CX Tunnel port. By default this is 5090.
- Click “OK” to create the bridge.
Step 2: Create a Bridge on the Slave Phone System
- In the 3CX Management Console of the “Slave” 3CX Phone System, Select the “Bridges” node and click “Add > Slave Bridge.”
- Enter a name for the bridge and assign the same virtual extension number as the one configured on the Master 3CX Phone System.
- Specify an “Outbound rule prefix” to be used for this bridge. I.e. if you specify 7, then a you must dial 7100 to reach extension 100 on the other 3CX Phone System. It could also be that the extensions on the other pbx start with 7 example 706, 708 etc.
- Specify the Authentication Password configured on the “Master” 3CX Phone System.
- In the remote PBX section, enter the Public IP or FQDN of the “Master” 3CX Phone System and the port (default 5060).
- Select if the remote PBX uses a tunnel connection or not. If yes, you must change the port to 5090.
- Click “OK” to create the bridge.
Step 3: Configure Presence across the Bridge
- Select if you want to “Publish Information” regarding presence to the other 3CX system. If yes “Add” which groups should publish presence.
- Select if you want to “Receive Information” - i.e. so that users in this 3CX system can see presence of users in other offices. Note that Receive information is available only in the Pro Edition.
- Now configure the IP or FQDN of the remote 3CX system. (If a tunneled connection is configured, this will be automatically populated.) If the webserver of the other 3CX Phone System is running on non default HTTP/HTTPS ports - example 5001, then you need to specify the port after the FQDN example “office2.3cx.com:5001.”
- Now “Add” the users or groups that are able to see this remote connection from within their client.
- Troubleshooting Remote Extensions and VoIP Providers Using the 3CX Firewall Checker.
- Take a look at the 3CX Advanced Training: Bridge Configuration video.
- Find a full guide on the 3CX Tunnel / 3CX Session Border Controller.