Configuring and Using the 3CX Skype gateway

Save money by connecting an IP PABX to Skype for low cost international calls from IP desk phones, not just PCs.

Skype is turning into an effective business tool, giving your clients cheap international calls, and free access to 800 numbers all over the world. But not everyone likes making calls from a PC. If you can bring Skype into a VoIP network with IP handsets, it can become just another way to make calls, only at much lower rates.

If you’re using the 3CX VoIP system, this is simple. You can treat Skype as just another gateway for VoIP calls, alongside the supported hardware and software gateways. 3CX has another advantage; unlike many other VoIP systems, it’s both simple and free. It runs on Windows Server and the management tools use the built-in IIS Web server (and run as an ASP.NET Web application). Installation is easy and the free version provides many of the telephony features that a small business will need. If your clients need more, you can add functionality with the pay-for options, which also include support. If you find 3CX popular among your clients, there’s a reseller programme.

Installing 3CX

You’ll need to deploy supported IP phones in the client’s network before you set up a 3CX system. Most common phones are supported, including Linksys, Cisco and Snom hardware, and there’s plenty of configuration information on the 3CX Web site. You can even use Windows Mobile phones with SIP clients (like SJphone or the client built into Windows Mobile 6.1). Our test system used a mix of Snom devices, including desksets and wireless DECT phones with 3CX running on a 64-bit Windows Server 2003 machine.

Decide how many digits to use for extensions before you start (depending on how many users there are and how many extra staff the business expects to take on). You also need to give 3CX the details of the SIP domain you’ll be using for your network. This will usually be the fully qualified domain name for your clients, though you can use alternative domain names, as well as IP addresses for your 3CX servers. 3CX can also work with existing mail servers to send voicemail and missed call notifications, making them part of users’ everyday tools and activities.

Configure your first extension

You’ll need to configure a 3CX VoIP server to use the Skype gateway. From the long list of supported PSTN gateways, choose the 3CX gateway for Skype. This will set up the VoIP server for use with Skype connections.
You’ll need to configure a 3CX VoIP server to use the Skype gateway. From the long list of supported PSTN gateways, choose the 3CX gateway for Skype. This will set up the VoIP server for use with Skype connections.

You only need to create one user to set up the 3CX system (you can add the rest through the Web user interface later) but this is an important extension –it’s the operator’s. Incoming calls are directed here and redirected to the rest of the network. You won’t need to set up a VoIP gateway as part of the installation either; instead you use the Web UI to add that later.

This is also where you register the handsets you intend to use with the server. There are different registration instructions for different handsets – including different handsets from the same manufacturer. 3CX provides a lot of documentation on its Web site, and you can follow the step by step instructions to configure your clients’ phones. The Snom devices we used could be also configured using the phones’ own on-board Web servers, filling in appropriate values and then rebooting to make the connection to the server. Phones configured to work with 3CX don’t need any further configuration to work with Skype, as the free Skype gateway does the rest for you.

Adding a Skype gateway

The original Skype gateway for 3CX was based on open source tools, and wasn’t the easiest piece of software to work with. It’s recently been replaced with a new, faster gateway, written in C++ rather than Java. Installation is now quick and easy, though you do need to be sure that you’re running it on a server with sound support and the appropriate sound drivers installed. You’ll also need to install Skype on the server and preconfigure a selection of user names for each channel you want to use.

Start by choosing the 3CX Gateway for Skype as a PSTN device in the 3CX Web interface. This will configure the ports used for your first Skype channel. You’ll need a channel for each line you intend to use, with one master channel to handle incoming calls. The gateway acts as a virtual extension which automatically maps incoming calls to the operator’s phone, which can then route the calls to the appropriate extensions.

Outgoing calls also need to be routed appropriately, especially if you’re using more than one gateway. One option is to use a call prefix to force routing via Skype, using the Skye gateway’s virtual extension as a route. If you have enough Skype accounts, then you can use two as additional back-up routes to allow users to make more than one call via Skype at a time. Make sure you configure 3CX to strip the prefix digits, so they don’t get sent out via Skype, which would leave users dialling the wrong number.

Note the line number and passcode generated by 3CX; you’ll need them to configure the gateway. You can now install the gateway software itself and configure that. You first need to specify the host name or IP address of the 3CX you’re using with the Skype gateway. While you’re likely to install the gateway on the same server as the 3CX PABX, you can load balance and use servers at the edge of the network to host multiple Skype gateways. The gateway will automatically create local accounts to host Skype processes, and you’ll be prompted to set the account prefix for these (so if you use ‘skypeaccount’ the accounts generated will be ‘skypeaccount1’, ‘skypeaccount2’, etc).

Set up Skype and Skype ports

You won’t need to change the advanced settings for the connection; the defaults are ideal for most installations. Click on the advanced option if you want to see what’s required, but there’s no need. You can now create your first Skype port, the inbound master port. Fill in the port IDs and passwords you created. The default local port for the connection is 6060. Additional ports increment the port number by two, so a second connection will be to 6062, a third to 6064, and so on. Skype will launch, and you’ll need to fill in the details of the Skype account you want to use for all incoming calls. You also need to approve access to Skype from the 3CX Gateway ; the Skype interface highlights this on screen.

Use the 3CX Outbound Call Rules to set up a number prefix users will need to start a Skype call. Stick with a single digit, as users also have to dial the full international number for every call.
Use the 3CX Outbound Call Rules to set up a number prefix users will need to start a Skype call. Stick with a single digit, as users also have to dial the full international number for every call.

You’re now ready to start receiving calls from Skype. Call your incoming Skype account (or an associated SkypeIn number) to test the connection. If you call from a Skype account, the user name will be the caller ID on the phone screen.

Next connect up a second Skype account to make outgoing calls. Click the Create button and make sure that you’re not creating an inbound master and that you specify a different Skype account. The process of creating and connecting an account is the same as for creating a master: again you authorise access in Skype. Once this is set up, go back to the 3CX Web interface to add a new PSTN gateway for outgoing calls. You’ll need to attach this gateway to the outbound call rule you created earlier.

As 3CX runs Skype in user processes, you won’t see the usual Skype interface. Use the Gateway monitor application to view the ports you’ve created – and check how much credit is available for outgoing calls. You can also see if any calls are in progress (useful for troubleshooting) and if you need to create new gateway ports to handle additional demand.

The combination of 3CX and Skype is very effective, though there’s one disadvantage you’ll need to keep in mind when training users. All calls need the full international dialling code, so a UK number needs to be prefixed with 0044 and a US number with 001. If users don’t use the full number calls won’t be completed, and all they’ll see or hear is a number that’s reported as busy.

Step by Step

  1. Start configuring the 3CX Skype Gateway by filling the details of the 3CX PABX (by name or IP address), and then the name that will be used to generate the user accounts that host Skype processes.

  2. Your first Skype channel needs to be an inbound master, using a Skype account with a SkypeIn number; this will handle incoming calls. It should be linked to a specific extension to allow receptionists or operators to route calls to the right person.

  3. While the 3CX Skype Gateway runs as a service, you can still use it to monitor calls and connections. You can see how much credit is available to each account, and whether a channel is in use or not.



Shopping for IP Phones

There are many different IP phones on the market, from basic to top of the line. Cisco uses its consumer and SME Linksys brand for VoIP hardware and VoIP specialist Snom’s range of devices is suitable for everything from small budget deployments to large scale high-end systems needing full featured phones and DECT wireless handsets. Little user training is needed, and as far as users are concerned, they’re just using a phone like any other.

VoIP handsets have all the features your clients look for in a business phone: support for conference calls, tools for managing voice mail – and large screens that can be programmed to deliver business and workflow information to users. Using VoIP and building it in to unified messaging servers like the latest Exchange releases (which 3CX supports without needing Office Communication Server) means calls can be tracked and managed, with information delivered straight to CRM systems.



3CX – free/from $375

3CX Skype Gateway – free



3CX Wiki
The free version of 3CX doesn’t include support, but the FAQ and Wiki have a lot of useful information:

Training videos about setting up 3CX, from the basics to more complex setups:

Windows-based IP PBX blog
This hands-on blog covers 3CX and other Windows-based IP telephony options:

3CX Worksighted
Another very technical blog, covering a range of unusual 3CX setups:

Unofficial 3CX Addons list
You can use 3C with Windows Mobile SIP phones, or to drive an intercom and a door opener, or to schedule wakeup calls and monitor a call queue - find the add-ones to do that and more here:

See also

Volume 2, Edition 1
Managing Skype in Business feature finder code 2222a.

Volume 1, Edition 2
Is hosted VoIP ready for small business feature finder code 1211a.




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Comments (2)
Posted: Aug, 23 2011

I have one doubt. Isn't it i cann call directly from skype to any international number? If so what is the benefit of having 3CX being integrated.

Thank you
Chris Ayres
Posted: Jan, 31 2012

Configuring Skype gateway

I just followed the instructions provided in this blog and found it quite helpful. Well, I managed to make it work fine but the issue starts on incoming calls. On incoming call I can hear the ring and skype user name is displayed but when call is answered, it gets dropped. I have almost checked it again, my bandwidth is fine too as i have already an account from the VoIP Service Provider(Axvoice) which is working fine. I wonder whats' going wrong.



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