Free SIP to SIP calls

There must be millions of SIP numbers out there. Is it possible to call them SIP to SIP for free? e.g. calls to enum numbers, Google Voice, Vonage, Magic Jack, etc… Why should it cost money to call these numbers when they should be reachable via SIP directly?

  1. Is it possible to call these numbers (enum, GV, magic jack, Vonage…)

  2. Is the FreePBX enum trunk working?

  3. Is it worth it?

  1. Yes if the provider publishes a SIP URI scheme for receiving calls

  2. ENUM works but few providers publish in it, so it is not worth it to configure

  3. Yes but only if you are frequently calling the same SIP-capable provider since you will need to configure the routes for it.


Does anyone know the SIP URI for google voice, Vonage, Magic Jack? Those 3 alone would probably cover millions of VoIP numbers.

Most carriers do not allow URL direct dialing for security reasons and want everything coming through SS7s and the PSTN and most PBXs won’t allow guest calling for the same reason.



I know some providers let you call between their accounts for free.

I am actually using this to let my parents call me for free using an ATA which uses one of my (sub)accounts.

For some unknown reason I have been unable to call them using what I believe should be their SIP URI (they don’t have a DID attached to that subaccount like I do so the only way to reach them would be to use the SIP URI), I get a weird message about an INVITE (shouldn’t they be the one getting the INVITE?).

Have a nice day!