3CX Month: Setting Up Bridges in 3CX

Every business day for the month of November, we will be posting a useful tip for 3CX, a powerful SIP-based unified communications platform.

Let’s say your business has grown to the point where you now have a remote office. An easy way to divide up the communications for this complicated set-up is to have a separate phone system for each office: home and remote. But you still want everyone to be able to talk with each other, and you don’t want to pay extra costs for calls. What do you do?

You set up a bridge. A bridge is a link between distinct phone systems. 3CX makes it simple and secure to bridge distinct 3CX phone systems.

There are two basic methods. For this example, assume that “2” extensions are for home office and “3” extensions for remote:

  • You define a prefix for each phone system that needs to be dialed before the extension. For example, extension 101 at home office would dial 3117 to reach extension 117 at the remote office.
  • You have the extensions for each bridge start with a unique first number. Compared with the last example, extension 101 from home would simply dial 317.

Sounds complicated? 3CX makes it simple!

For this to work, one phone system needs to be in control. The controlling system is called the master, while the other one is called the slave. That means you need to create a master bridge and a slave bridge. For our example, we’ll make home office the master and remote the slave.

Creating a Master Bridge in 3CX

To start, go to the 3CX Management Console and go to Bridges > Add > Master Bridge.

Give it a name (“Home Office”) and specify a unique virtual extension number, which 3CX will use to connect the two systems. Make sure this number is not in use for any other reason on either system. Note it down, because you’ll need it when setting up the slave bridge.

Then, specify an “Outbound rule prefix to reach remote 3CX PBX.” What is this?

When you to connect to an extension at the remote office, you need to dial a prefix before dialing the extension. It’s suggested that you just use a single number. For example, if you set the prefix to 3 and you want to reach extension 125 at the remote office, you would dial 3125.

Remember, this prefix is for dialing from the master bridge to the slave bridge. It’s the outbound prefix, not the prefix for inbound calls to the master bridge.

But what if you just want to be able to dial the remote office without worrying about prefixes?  All you need to do is this:

  • Set the Outbound Rule Prefix to a number.
  • Set all extensions for the remote office to begin with that number. For example, if the outbound prefix on the master bridge is 3, set all extensions on the slave bridge to begin with 3: 301, 302, 303, etc.
  • That’s it!

There are only a few more fields to fill out before the master bridge is configured.

Set the maximum number of simultaneous calls to whatever you want.

Enter an authentication password that’s hard to guess. As with the virtual extension number, you’ll need to match this password exactly when setting up the slave bridge.

Finally, choose if you want to use a public SIP/RTP connection or the recommend secure 3CX Bridge Tunnel connection. If you use the 3CX Tunnel, set the port to 5090.

Click ok, and the master bridge is created!

Creating a Slave Bridge in 3CX

If you can create a master bridge, you can create a slave bridge. In fact, it’s the exact same process with almost the exact same information.

In the 3CX Management Console, go to Bridges > Add > Slave Bridge.

Enter the information. All the information should be exactly the same, except for these two:

  1. Name. Give the slave bridge a different name (“Remote Office”).
  2. Outbound prefix. Set a different number as a prefix.

Why different? Because it’s used to dial from the slave bridge to the master bridge.

Let’s say you set the prefix to 2. For someone at the remote office to dial someone at home office, they would need to use that prefix to reach them: e.g. to reach extension 101, they would dial 2101. Or you can set all the extensions of home office to begin with 2. Then people at the remote office would only need to dial the extension: e.g. to reach extension 201, they would simply dial 201.

Note: Make sure that all the other information is identical to what you entered for the master bridge. The information is case-sensitive. Make sure if you’re using 3CX Tunnel that the port is set to 5090.

And that’s all you need for a basic bridge set-up! That wasn’t so bad, was it?

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