Earlier this year we demonstrated how to set up a publicly-accessible Asterisk® server to enable free worldwide calling using SIP URIs which are email-like addresses for VoIP and video calls. But not everyone has an Asterisk server so today’s tutorial extends free calling to everyone with a Windows or Linux PC, a Mac, or any smartphone or tablet. All you need is a desktop computer with wired or wireless Internet access or, on a smartphone or tablet, a cell data plan or WiFi connection will suffice. When friends sign up, their calls also will be free.

The secret sauce on all of these platforms is the Linphone app (shown above) which can be downloaded and used at no cost. Source code is available for those that want it. Use it as often and for as long as you like. Here are the Linphone download links for each of the platforms:

The only other piece you’ll need to get started is a free Linphone SIP account. Sign up here. Once you’ve signed up, simply respond to the confirmation email to activate your account. Your registration gets you credentials to plug into your Linphone app that you downloaded above. In addition, it gets you a free Linphone SIP URI which looks something like this: yourname@sip.linphone.org. This is the SIP URI address that anyone in the world can use to contact you. Here are the pieces you’ll need to plug into your desktop or smartphone app:

  • Account Name
  • Account Password
  • Domain: sip.linphone.org

Be very careful not to lose your password. You can’t retrieve it, and you can’t change it without knowing the original password. All you can do is delete your account and start over.

The Linphone feature set is downright impressive. Here’s what you and your friends will be using at zero cost:

IMPORTANT TIP: Missing audio or one-way audio is a common problem on SIP calls. For best results, configure your account in the Linphone app to use UDP for the Transport, disable the Outbound Proxy, configure stun.linphone.org as the Stun Server, and enable ICE. In Network settings, turn off IPv6 and Media Encryption. In Audio settings, enable Opus, G.722, PCMU, and PCMA only. In Video settings, enable both VP8 and H.264. Then close the app and reopen it.

Once you have your Linphone credentials, another option in addition to using one of the SIP clients above is to acquire a stand-alone SIP telephone which can easily be connected to your Linphone SIP account. While there are literally hundreds of SIP telephones from which to choose, here’s a $35 offering from Grandstream that we use. It’s available from Amazon.1

Unlike other proprietary communications apps, the beauty of using Linphone with its native SIP URI support is you can call any SIP phone in the world for free whether the recipient uses Linphone or not. For example, to annoy your friends and spammers, you can transfer their calls to Lenny: 2233435945@sip2sip.info or 883510001198938@sip.inum.net. And here are some other SIP URI calls you might want to try. Store them in your Linphone Phonebook.

Yahoo News Headlines - news@demo.nerdvittles.com
Yahoo News Headlines - 951@demo.nerdvittles.com
Weather by Zip Code  - weather@demo.nerdvittles.com
Weather by Zip Code  - 947@demo.nerdvittles.com
Directory Assistance - information@demo.nerdvittles.com
Directory Assistance - 411@demo.nerdvittles.com
Lenny for Spammers   - 53669@demo.nerdvittles.com
Technical Support    - 0@sip.incrediblepbx.com
Call Any TollFree #  - **1800XXXXXXX@tollfree.future-nine.com

There are now more than 2,000 VoIP networks worldwide that support SIP URI access. Any person or organization with an account on any of these networks can be reached at no cost via SIP URI or via several hundred PSTN numbers. Using a SIP URI dialing prefix, you can call any referenced network@sipbroker.com. For example, *656news@sipbroker.com would reach the Nerd Vittles News Headlines from Yahoo. Or choose a local access number from the SipBroker worldwide directory, e.g. 702-789-0530 and then dial *656951 at the prompt.

Of course, every 3CX platform provides dedicated SIP URIs for every extension on the PBX. Our recent article covers adding SIP URI access to any Asterisk PBX.

If you want to associate a phone number with your Linphone SIP URI, you can do it in a couple of ways. First, using a smartphone, you can link your cell number to Linphone within the Linphone app itself. If you have a free DID from IPComms, you can point it to your Linphone SIP URI. If you have a $1/month CallCentric DID, it can also be pointed to your Linphone SIP URI. A 25¢/month iNum DID from LocalPhone.com also can be pointed to your SIP URI. LocalPhone supports Nerd Vittles through referral revenue from your 25¢ investment. 🙂

Speaking of iNUMs, you can reach anyone with an iNUM DID by dialing the iNUM number in SIP URI format: 8835100xxxxxxxx@sip.inum.net. One of the real beauties of signing up for an iNUM number as well is that it can be reached in most places around the globe by dialing a local number from any telephone. As part of the iNum initiative, local access numbers have been established in more than 50 countries around the globe. By placing a local call from any telephone to one of these local access numbers, any individual with an iNum phone number anywhere in the world can be reached without further cost. Here is a current list of the local access numbers. If the link is down (frequently), try here or here or the iNUM listing here. Once your call is answered, simply enter the 15-digit iNum phone number you wish to reach, and you will be connected. It’s worth pointing out that iNUMs aren’t as unwieldy as they may appear. The numbers always begin with 8835100 followed by 8 digits starting with a zero.

More iNUM details are available here. If sip.inum.net is down, try

Let’s tie all the pieces together now. Linphone gives you and your friends a free SIP URI as well as a SIP client for any platform to make and receive SIP voice and video calls. You can associate this SIP URI with your cellphone number as well as a free or almost free phone number (DID) that’s available from IPComms, CallCentric, and other providers. If you sign up for a LocalPhone iNUM number, you also can associate it with your Linphone SIP URI. So you can be reached on your Linphone client by SIP URI, by iNUM, and by regular phone numbers. You can place unlimited calls to any SIP URI or iNUM worldwide at no cost. What’s not to like?

Deploying Linphone as an Asterisk Trunk

If you don’t have an Asterisk PBX, you can stop reading here. The good news is you can also use a Linphone SIP account as a SIP trunk on your Asterisk PBX. Once configured, you can add an Incoming Route and send the incoming Linphone SIP URI calls to any destination desired: an extension, a ring group, an IVR, or even a Conference Room. Using the FreePBX® or Incredible PBX® GUI, create a chan_SIP Trunk and name it linphone. In the PEER DETAILS, enter the following using your actual Linphone username and password:


For the Registration String: your-username:your-password@sip.linphone.org/99999

Next, create an Inbound Route using 99999 as the DID entry. Route the call to your desired destination, SAVE your settings, and you’re in business.

There’s one more nice surprise. Linphone accounts work much like the old key telephones and Google Voice setup that we all knew and loved. What that means is you can register the same Linphone account in multiple places, e.g. as an Asterisk trunk and elsewhere using one of the Linphone softphone apps. When incoming calls to your SIP URI arrive, they will ring on both your Asterisk PBX and your Linphone softphone as long as you haven’t routed the Linphone trunk to a destination that automatically answers the calls such as an IVR.

HINT: If you’re using dual registrations and routing the Linphone trunk to an extension, we recommend disabling voicemail on that extension so that Asterisk doesn’t automatically answer the call and send it to voicemail when the extension is not registered or answered.

To make outbound calls from extensions on your PBX using the Linphone trunk, the easiest way is to create custom extensions in the [from-internal-custom] context in /etc/asterisk/ extensions_custom.conf. Make up an unused extension number (90210 in this example), enter the Linphone account name you wish to call (acctname in this example), save the file, and reload your dialplan: exten => 90210,1,Dial(SIP/acctname@linphone).

Another way to create a Custom Extension is using the FreePBX or Incredible PBX GUI. Under Applications -> Extensions -> Add Custom Extension, assign an extension number for the extension. Click on the Advanced tab and enter SIP/acctname@linphone in the Dial field. Click Submit button and reload the dialplan at the prompt. Enjoy your worldwide free calling.

Originally published: Monday, April 29, 2019

Need help with Asterisk? Visit the PBX in a Flash Forum.


Special Thanks to Our Generous Sponsors

FULL DISCLOSURE: RentPBX, Amazon, Skyetel, Vitelity, DigitalOcean, Vultr, Digium, Sangoma, 3CX, TelecomsXchange and others have provided financial support to Nerd Vittles and our open source projects through advertising, referral revenue, and/or merchandise. We’ve chosen these providers not the other way around. Our decisions are based upon their corporate reputation and the quality of their offerings and pricing. Our recommendations regarding technology are reached without regard to financial compensation except in situations in which comparable products at comparable pricing are available from multiple sources. In this limited case, we support our sponsors because our sponsors support us.

BOGO Bonaza: Enjoy state-of-the-art VoIP service with a half-price offer on up to $500 of Skyetel SIP trunking service with free number porting when you sign up for a Skyetel account. No restrictions on number of simultaneous calls and triple data center redundancy assures that you’ll never have a failed call. Tutorial and sign up details starting April 1st.

Special Thanks to Vitelity. Vitelity is now Voyant Communications and has halted new registrations for the time being. Our special thanks to Vitelity for their unwavering financial support over many years and to the many Nerd Vittles readers who continue to enjoy the benefits of their service offerings. We will keep everyone posted on further developments.

RentPBX, a long-time partner and supporter of PIAF project, is offering generous discounts for Nerd Vittles readers. For all of your Incredible PBX hosting needs, sign up at www.RentPBX.com and use code NOGOTCHAS to get the special pricing. The code will lower the price to $14.99/month, originally $24.99/month. It’s less than 50¢/day.

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  1. This phone requires a wired network connection. Some of our purchase links refer users to Amazon when we find their prices are competitive for the recommended products. Nerd Vittles receives a small referral fee from Amazon to help cover the costs of our blog. We never recommend particular products solely to generate Amazon commissions. However, when pricing is comparable or availability is favorable, we support Amazon because Amazon supports us. []

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