Programmable SIP

NOTE: Programmable SIP is currently in Developer Preview. In order to get set up with Programmable SIP, please contact Support or your Account Manager.


Nexmo’s Programmable SIP enables you to integrate your existing SIP Infrastructure with Nexmo’s powerful conversational communications platform. This integration will enable you to easily connect to mobile, landline, SIP and WebRTC endpoints, including browsers and mobile applications. It will also bring Voice API functionality, such as multichannel recording, IVR, Text to Speech, WebSocket connectivity for AI integrations, and the power of contextual conversations to your platform.


Nexmo SIP Domains

A Nexmo SIP Domain contains configuration you need to connect to Nexmo SIP endpoints and link to your Nexmo application.

To route a SIP call to your Nexmo application, you need to create a unique Nexmo domain, such as yourcompany. The domain name will form the SIP URI, for example, and any calls routed to that SIP URI will be routed to your application NCCO answer_url.

The authentication method will be determined within your configuration of the Nexmo domain. Nexmo will authenticate the request and forward it to your application.

Some example domains:

Authentication - Access Control Lists

IP addresses of your devices and endpoints can be configured to reach your Nexmo application. Nexmo will only accept calls from the IP address list that is configured for your domain. This method will enable you to whitelist your endpoints’ and devices’ IP Addresses per your application.

Domain Based Routing

Calls made to a Programmable SIP domain must be handled at a regional level. You must use a Request URI with a regional domain. Please be aware that a Request URI without a regional component in the domain will fail the call.

The following code will indicate to Nexmo that you want this SIP call to be handled in the EU:

Available domains are the same as the A records: USA Europe Asia Pacific

Custom SIP Headers

You can specify any additional headers you need when sending a SIP Request. Any headers provided must start with X- and will be sent to your answer_url with a prefix of SipHeader_. For example, if you add a header of X-UserId with a value of 1938ND9, Nexmo will add SipHeader_X-UserId=1938ND9 to the request made to your answer_url.

CAUTION: Headers that start with X-Nexmo are not sent to your answer_url.

Receiving Calls From Nexmo

You can use the Voice API NCCO connect action to connect a call to your SIP endpoints. The detailed documentation is here.

SIP Connect

The SIP Connect feature support will continue where you can dial your virtual number via your SIP endpoint that is attached to your application. Digest Authentication is the accepted authentication method for SIP Connect.

To test this functionality have your PBX forward calls to Here is an example of doing so with an Asterisk extension, transmitting a custom header that will be sent to your answer_url:

exten => 69100,1,SIPAddHeader(X-UserId:ABC123)
exten => 69100,2,Dial(SIP/nexmo/14155550100)

Further information