Friday, April 17, 2009

Forwarding SIP Calls to Google Voice

Warning/Disclaimer: This information is based on unsupported features of Google Voice and as such may change or be blocked at any time. Don’t rely on it for important communication needs.

Ok, having said that, let’s talk about the ability to forward SIP calls to your Google Voice number via a direct SIP-to-SIP connection which in turn are forwarded by Google to your registered phones.

This is a cool feature for people who already use SIP based phones because it extends the receiving end of the connection to your mobile and landline phones. The list of potential uses and benefits is pretty long and I’ll spare you from having to read through a regurgitated list of them from me.

To make this as simple as possible and leave you some flexibility in the configuration side should it need to change, you’re going to want two Gizmo accounts. This is assuming you want the ability to receive calls via SIP as well (see my previous blog post on how to set up Gizmo/X-Lite with Google Voice).

SIP Forwarding Visio

This post just concerned with the Gizmo Forwarding Account highlighted in the diagram above.

If you already have a Gizmo account and you’ve shared that SIP number with others, you’ll want to create a new account to use as your Gizmo Receiving Account and use your existing one as the Gizmo Forwarding Account. That way you won’t have to give out a new number.

Before you can configure your Gizmo account to forward calls, you need to know your Google Voice SIP address. And herein lies the tricky part. The Google Voice connection to Gizmo is a two-way capable connection but they don’t give you any information on how to receive calls via that connection. Why not? The list of reasons that people have suggested could fill a blog post by themselves. My feelings are that since Google Voice (and Grand Central before it) haven’t blocked incoming calls, they condone it’s use, but just can’t commit to supporting it so they don’t mention it. A quick search of the internet shows that this inbound connection has existed for a long time and they would have closed it by now if they wanted it closed. So for now, we’ll make use of it.

Here’s the format of the Google Voice SIP address:


The first part is your Google Voice phone number followed by the @ symbol then a Google Voice server IP address and then a colon and port number. This number is the from address that is passed to Gizmo/X-Lite when a call comes in from Google Voice. The “.11” portion of the IP address changes from time to time and is sometime “.14” or “.15” among others. I suggest trying “.11” for now and if that fails you can try “.14” or “.15”.

With your Google Voice SIP address in hand, setting up a Gizmo account to forward is really easy. Here’s a screenshot.

Gizmo Forwarding Account

In the Forwarding Gizmo5 Calls section of your account page, set the status to “Forwarding All Calls” and then set the ID radio button to SIP and enter your Google Voice SIP address and hit save. You can also turn off the Gizmo voicemail while you’re here if it’s active.

That’s literally all there is to it. You can now have people call your Gizmo Forwarding Account’s SIP number and they’ll be automatically forwarded to your Google Voice number which will ring your phones.

The beauty here is you have a number that you can give out and if things stop working you still have options. You can fix the forwarding number if it changes, or you can forward directly to your Gizmo Receiving Account.

Since all the technology is in place for this to work quite seamlessly, I really hope the Google Voice powers that be make this an official feature. If it get’s turned off at some point it will likely be due to some sort of legal, regulatory or outside business pressure.

The world’s changing and Google Voice is leading the way. I hope it’s allowed to continue.

Note: Should things change with this “feature”, I’ll update this post.


  1. Well, the publicity of this post will ruin some people's little secret. I am sure someone hereafter will "officially contact" Google and notify them the "security hole", and then the party is over.

  2. isnt this what google is doing anyway when i call from a registered phone and get VM then dial 2? i dont know if google could close this IP since it has to be used.

  3. SIP connects to Google Voice not allowed since 05/08/09. It is over, done, toast. LHM

  4. is there no other workaround for this? any updates to be found anywhere?

  5. So, if you spend some cash and buy yourself a (eg Linksys) voip adapter, yes, I have it working here. I have port 5060 open to the PAP2, and a user account for line 1 (eg fubar). This is in fact set up for a voip provider - but ythat doesn't affect the pattern in use here - you could just put a fake account in - you just need a username so sip:username@yourip can be reached by any sip phone - of course where yourip is the more complex part of the story. I use dyndns running on a readynas I happen to have available to redirect a domain I happen to own but there are plenty of free dyndns urls you can get
    . The whole thing sounds more fearsome than it is. Of course, google voice calls my gizmo number which redirects to sip:username@yourip.

    Good luck

  6. I gave it a try today. Using the information as suggested here results in the calling party hearing a phone ringing, but none of your Google Voice phones will ring. The call will not go to voicemail, and the setting Do Not Disturb on makes no difference (the calling party still hears ringing).

  7. I have been using various SIP accounts for the past few years.
    I had X-Lite, FWD, GIZMO, GrandCentral, etc. I could get a call at my GrandCentral number and redirect it any way I liked, including to my MAC and/or a plain SIP phone. Thus I could get a call anywhere I was at any given time. Calls from Gizmo to Gizmo were free, exactly like SKYPE. A few times I emailed them and promptly got a reply. There was always a way to get an answer. Then enter GOOGLE (Gvoice), they kept the same setup and my number, but something started to change. No more GVmobile, now there is Gvoice for iPhone, but, for me, it doesn't work as before. From Europe, while on WiFi I dial any number and I get a screen reading "+19165383466 CANCEL - CALL"
    What does it means? Mistery, no way to find out. So, for once, I tap CALL: "the number you dialed cannot be reached". Weird :-( And, last but not least, I was charged right away a few cents by the local carrier. Heck I was on WiFi. How was that possible?
    While still on WiFi I removed the SIM card, and got "CALL FAILED". So I guess that somehow either Google or Apple or the ISP have made arrangements (undocumented) that WiFi Gvoice calls would have to go to that 19165383466 and be charged by the carrier.
    However that alone doesn't explain the charge even if the call doesn't go thru.

    Anyone can please clarify this? It never ever happen to be charged while using FRING or SKYPE with iPhone on WiFi. I really wish to know. How can that be possible?

    It would be nice if Google could post/email some infos about what is going on, what about the existing credit?

  8. how would I get around a VPN to makes calls from gv/gizmo5/x-lite?

  9. still no in/out SIP URI google? very gay of you!

  10. GV is created/bought by Google, inc.. That said, it has to earn money for them. Users are lured into something that was too good at the beginning only to find out not so in the end. GV has to make money for Google. Bottom line is GV+Gizmo5= Expensive.
    GV stops forwarding calls to SIP devices= abandonment from users who want more freedom.
    Spend half a day searching and people will find a good cheap SIP provider.

  11. GV --> IPkall 425 --> LP sip number ( ) --> Any international mobile number (low call forward rate)

  12. You can use nokia n95 or iphone or android phones with voip technology + WiFi.


  13. Thanks for the post. I really like this info.

  14. hi, I want to configure the x-lite softphone with my google voice acc, but I can't open an accounts with Gizmo?? so.. what can i do? :)thanks!

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