Trunks using 3CX: Part 2

The next wizard screen is for Outbound Call Rules. Let's go over it enough so that you can setup a simple rule.

We start off with a name. This can be anything you like but I prefer something meaningful. For our example I want to dial 9 to use the analog line, and only allow extensions 100-102 to use this line. I also only want to be able to dial certain phone numbers. Then I have to delete the 9 before it goes out to the phone carrier. Let's have a look at each section of this screen:

Calls to numbers starting with (Prefix)

This is where you specify what you want someone to dial before the line is used. You could enter a string of numbers here to use as a "password" to dial out. You don't just let anyone call an international phone number, so set this to a string of numbers to use as your international password. Give the password only to those who need it. Just make sure you change it occasionally in case it slips out.

Calls from extension(s)

Now, you can specify who (by extension number) can use this gateway. Just enter the extension number(s) you want to allow either in a range (100-110), individually (100, 101, 104), or as a mix (100-103, 110). Usually, you will leave this open for everyone to use; otherwise, you will restrict extensions that were allowed to use the gateway, which will have repercussions of forwarding rules to external numbers.

Calls to numbers with a length of

This setting can be left blank if you want all calls to be able to go out on this gateway. In the next screenshot, I specified 3, 7, 10, and 11. This covers calls to 911, 411, 555-1234, 800-555-1234, and 1-800-555-1234, respectively. You can control what phone numbers go out based on the number of digits that are dialed.

Route and strip options

Since this is our only gateway right now, we will have it route the calls to the Patton gateway. The Strip Digits option needs to be set to 1. This will strip out the "9" that we specified above to dial out with. We can leave the Prepend section blank for now.

Now, go ahead and click Finish:

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Once you click Finish, you will see a gateway wizard summary, as shown in the next screenshot. This shows you that the gateway is created, and it also gives an overview of the settings. Your next step is to get those settings configured on your gateway.

There is a list of links for various supported gateways on the bottom of the summary page with up-to-date instructions. Feel free to visit those links. These links will take you to the 3CX website and explain how to configure that particular gateway. With Patton this is easy; click the Generate config file button.

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The only other information you need for the configuration file is the Subnet mask for the Patton gateway. Enter your network subnet mask in the box. Here, I entered a standard Class C subnet mask. This matches my 192.168.X.X network. Click OK when you are done:

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Once you click OK, your browser will prompt you to save the file, as shown in the following screenshot. Click Save:

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The following screenshot shows a familiar Save As Windows screen. I like to put this file in an easy-to-remember location on my hard drive. As I already have a 3CX folder created, I'm going to save the file there. You can change the name of the file if you wish. Click Save:

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Now that your file is saved, let's take a look at modifying those settings. Open the administration web interface and, on the left-hand side, click PSTN Devices. Go ahead and expand this by clicking the + sign next to it. Now, you will see our newly created Patton SN4114A gateway listed. Click the + sign again and expand that gateway.

Next, click the Patton SN4114A name, and you will see the right-hand side window pane fill up with five separate tabs.

The first tab is General. This is where you can change the gateway IP address, SIP port, and all the account details. If you change anything, you will need a new configuration file. So click the Generate config file button at the bottom of the screen. If you forgot to save the file previously, here's your chance to generate and save it again:

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On the Advanced tab, we have some Provider Capabilities. Leave these settings alone for now:

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We will leave the rest of the tabs for now. Go ahead and click the 10000 line information in the navigation pane on the left.

These are the settings for that particular phone port (10000). The first group of settings that we can change is the authentication username and password. Remember, this is to register the line with 3CX and not to use the phone line.

The next two sections are about what to do with an inbound call during Office Hours and Outside Office Hours. I didn't change anything from the gateway wizard but, on this screen, you can see that we selected Ring group 800 MainRingGroup. This is the Ring group that we configured previously.

We also see similar drop-down boxes for Outside Office Hours. As no one will be in the office to answer the phone, I've selected a Digital Receptionist 801 DR1.

In the section Other Options, the Outbound Caller ID box is used to enter what you would like to have presented to the outside world as caller ID information. If your phone carrier supports this, you can enter a phone number or a name. If the carrier does not support this, just leave it blank and talk to your carrier as to what you would require to have it assigned as your caller ID.

The Allow outbound calls on this line and Allow incoming calls on this line checkboxes are used to limit calls in or out. Depending on your environment, you might want to leave one line selected as no outbound calls. This will always leave an incoming line for customers to call. Otherwise, unless you have other lines that they can call on, they will get a busy signal.

Maximum simultaneous calls cannot be changed here as analog lines only support one call at a time. If you changed anything, click Apply and then go back and generate a new configuration file:

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For the most up-to-date information on configuring your gateway, visit the 3CX site:

We will go over a summary of it here:

Since nothing was changed, it is now time to configure the Patton device with the config file that we generated from the 3CX template. If you know the IP address of the device, go ahead and open a browser and navigate to that IP address. Mine would be If you do not know the IP address of your device, you will need the SmartNode discovery tool. The easiest place to get this tool is the CD that came with the device. You can also download it from, or search the Patton website for it.

Go ahead and install the SmartNode discovery tool and run it. You will get a screen that tells you all the SmartNodes on your network with their IP address, MAC address, and firmware version. Double-click on the SmartNode to open the web interface in a browser.

The default username is administrator, and the password field is left blank.

Click Import/Export on the left and Import Configuration on the right. Click Browse to find the configuration file that we generated. Click Import and then Reload to restart the gateway with the new configuration.

That's it . We can now get incoming calls and make an outbound call.

Creating a SIP trunk

Now it's time to create a SIP trunk. The best thing to do is use one of the supported VoIP providers. You can use anyone if you get the correct information but, if you have problems, 3CX won't be able to help you out.

Just like setting up the PSTN line, you can get to the VoIP provider wizard in the same manner. I'm going to click Add VOIP Provider Wizard on the top menu bar. Pick the method you are most comfortable with.

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The first thing you want to do is see which VoIP providers are supported and set up an account on their website. While the 3CX wizard is quick and easy, it cannot create your account with an ITSP. As I'm in the US and Callcentric lines are free (as long as the call is to another Callcentric customer), I am going to use a fake one to get us started. Go ahead and set up the account with the provider of your choice, and get your account details. Once you get the account information, it's time to move on and enter it into 3CX so that you can make calls.

It's time to enter the VoIP provider name that you want to use. Select the VoIP provider that you signed up with and click Next:

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The next screen is for our information only. If we had chosen a generic VoIP provider, we would need to enter the SIP server hostname or IP, the SIP Server port, and the Outbound proxy hostname or IP, and the Outbound proxy port. As this is a supported provider, 3CX has this information in the wizard template. Click Next:

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Now in the Account Details section, enter the phone number that we were assigned from the provider in the External Number field, and also enter the username and password.

The next section is to define how many Simultaneous Calls we can have at one time on this account. This is one of those providers that allow multiple concurrent calls, which is great for the small business or home office. Enter the appropriate number and click Next:

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Just like our PSTN call processing, we have the same set of options for our VoIP provider when a call comes in. Here, I wanted the incoming calls to go to the 802 Sales ring group during office hours. Once everyone has left for the day, I will have it go to the voicemail box of 104 Zachary Alan. Click Next:

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Now, we need an Outbound Call Rule. As we already went over most of these options, I'm going to make only one change.

As VoIP calls are less expensive than my PSTN calls, I want to allow everyone to use it. So, "no rules" in the upper section this time.

In the Make outbound calls on section, we want everyone to use the Callcentric route. We didn't use the Calls to numbers starting with (Prefix), so we don't want to strip any digits. However, we do want to Prepend a 1 before every call. Most VoIP providers treat every call as though it is long distance, even if it's across the street. To help avoid having people dial "1" with every call, we can have 3CX do this automatically. Click Finish:

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In the navigation pane on the left-hand side, click VOIP Providers and expand it by clicking the + sign next to it:

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In the right-hand window pane, we can see our information for this provider. If you need to change any of this information (like fixing a typo during the wizard), go ahead and do so here:

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Click on the Advanced tab, as shown in the following screenshot. This screen is a little different from the PSTN screen as we now have Registration Settings, too. These settings define how often the trunk line re-registers with the VoIP provider. It is a good thing because if the time was indefinite and your Internet went down, 3CX would still try to make calls on this line.

The bottom section is for Codec priorities. We also see a Which IP to use in 'Contact' field for registration setting in the Registration Settings section. If you have a static public IP, you can set it here. If you are using a dynamic IP, you will want to leave the default setting as External (STUN resolved). STUN is Simple Traversal of UDP through NAT. Some ITSPs support STUN while others do not. For a business, you will probably have a static IP. Most home Internet connections will be dynamic, and you will get better results if you have STUN.

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Now go ahead and click the line information for this VoIP provider in the left-hand window pane. The VoIP provider name is for all the lines under this account. If we had a carrier that did not support concurrent calls, we would have had to sign up for more lines with the same carrier. We can then specify what to do with each line:

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In the right-hand pane, we now see the details for this particular phone number. The only thing I want to change from the default is the Outbound Caller ID. As this provider supports what you want to use for caller ID information, I can specify my name here. Click Apply when you are done with these changes:

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We have finished the SIP trunk settings. Now, we need to assign a DID number to the SIP trunk. This number is used to identify the line and helps us create inbound rules. On the VoIP providers settings, there is a tab named DID. Add your assigned DID number(s) to this trunk by entering them, and then click Add. When you are done entering the DID number(s), click OK or Apply at the bottom to save them. Now, give it a try and see if you can make outbound calls.

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In this article, we discussed why you need a trunk, what you need for a PSTN line, what to look for in a VoIP provider, the equipment needed, analog lines, call quality, disaster recovery, and finally how to integrate a trunk into 3CX using the easy-to-use wizards.

That is a lot of information, but it's all needed to connect to anyone outside your network.

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