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Configuring Call2teams for use with Dial 9 SIP trunks

This guide allows you to configure a Call2teams instance to connect your Dial 9 SIP trunking account through to Microsoft Teams.

Configuring the SIP Trunk

To get started in Call2teams, you'll need to configure a new Custom Trunk, and set the Country to United Kingdom.

Add your Dial 9 numbers within the Trunk Number Ranges (if you have a single number, just add that number on its own), then enter individual numbers as service numbers in +E164 format, i.e. +443300880900.

Enter sip.dial9.co.uk (or your Partner domain if configuring a SIP trunk within your Dial 9 Partner service) as both the SIP Domain and SIP Proxy, select Static IPs as the Authentication Type then enter the IP addresses advised within our firewalls guide.

Configuring the Calling Policy

Within the Calling Policy, set the Protocol to UDP, Propagate Refer to Teams handles transfers, Suppress Contact Data Param as No, then Encrypt Media to No.

Finally, set E164 Number Format to E164 without +, From header to Trunk Caller Id and P-Asserted-Identity Header to Not Present.

At the bottom of this section, you'll be advised of two Current SBC IPs - each of these needs to be added to Dial 9 as a trunk that authenticates by IP address. You will also be shown an SRV hostname, this needs to be added as your SIP server, and any SIP URLs require numbers to be entered in +E164 format.

An example SIP URL would therefore look like +443300880900@123123123123123.call2teams.com.

With static IP authentication, Call2teams uses a SIP server and SIP URLs for incoming calls. SIP servers and SIP URLs are marked as deprecated in Dial 9 Connect but continue to work. Alternatively, you can connect Call2teams using a username and password trunk, as described below.

Using a username and password trunk

Instead of static IPs, Call2teams can register with a Dial 9 trunk that authenticates with a username and password. In this case, you don't need to add the Current SBC IPs as trunks, or create a SIP server and SIP URLs, in Dial 9.

  • Create a trunk in Dial 9 Connect that authenticates with a username and password.
  • In your Call2teams Custom Trunk, select Registration as the Authentication Type.
  • Enter sip.dial9.co.uk as the SIP Domain.
  • Enter the trunk's full username from Dial 9 Connect, including the prefix, as both the Username and Auth Username, and the trunk's password as the Password.
  • Configure the Calling Policy as above, including E164 Number Format set to E164 without +, which matches the format Dial 9 uses when sending calls to your trunk.
  • In Dial 9 Connect, set each number's destination to Send to a trunk and select your trunk.

Trunks always use E.164 format, so the CLI format change described under Teams click-to-call below isn't needed with this setup.

Further information on setting up the connections within Dial 9 can be found in our Setting up a SIP trunk guide.

Teams click-to-call (calling customers back)

We've been made aware of an issue with some Teams calls through the click-to-call/call log functionality not dialling out correctly, which we've narrowed down to how the call is presented when calling back a customer.

This is resolved by updating the CLI format, within your SIP server settings in Dial 9 to e164 rather than passthrough.

A note on emergency service calls

When sending emergency service calls (i.e. 999) through your PBX, you must send the dialled number as just 999. For handling 112 calls (the European emergency services number), you must transpose 112 to 999 directly.