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Dial-Tone Options in Microsoft Teams

By virtuoso


May 8, 2022


A few weeks ago we discussed the game-changing Microsoft Teams and it’s many benefits for the modern workplace. This week we’re looking at the recent announcement from Microsoft that Direct Routing will be made available for all Office 365 customers.

Direct Routing 

Direct Routing allows organisations to use their existing telecommunications provider or PBX equipment to enable employees to make and receive telephone calls in Microsoft Teams. Organisations now have two different scenarios to choose from that will enable dial-tone calling for Microsoft Teams. It’s noteworthy at this point to mention that Direct Routing is not available for Skype for Business Online.

The first scenario allows organisations to connect their own Session Border Controller to almost any telephony trunk or PBX equipment and to Office 365 Microsoft Teams with Phone System. This adds flexibility for organisations to use Microsoft Phone system by allowing them to configure inter-operability between existing on-premises equipment and Microsoft Teams. In practice, this mean that organisations typically choose Direct Routing when:

  1. Microsoft Calling Plans are not available
  2. The organisation requires connection to third party solutions such as call centres or analog devices such as paging systems or elevators
  3. The organisation has an existing contract with a telecommunications provider

What you need

This is a feature of Microsoft Teams that will greatly benefit a lot of small businesses in the UK. Once your business is ready to implement Teams then you will need a Session Border Controller which has a public IP address. The SBC can use NAT and it must be assigned a Fully Qualified Domain Name (FQDN). The FQDN must be published externally. In addition, the SBC must have a public certificate installed which contains the FQDN in the subject, common name, or subject alternate name fields. Please note that Direct Routing does support wildcard certificates. Here’s a handy list of the other requirements to implement Direct Routing with Microsoft Teams:

  • Office 365 tenant
  • Users must be homed in Office 365. It is not possible to enable Voice in teams for a user homed in an on-premises deployment of Skype for Business or Lync Server.
  • One or more domains added to the Office 365 tenant. The default O365 domain * cannot be used
  • Users must have the following Office 365 Licenses assigned:
  • Skype for Business Online (Plan 2)
  • Microsoft Phone System
  • Microsoft Teams
  • Microsoft Audio Conferencing


The second scenario allows organisation to use Microsoft Teams with Phone System without having on-premises equipment. This Partner Hosted offering enables organisations to completely move into a cloud solution. Below are a few of the Telecommunications providers which offer Direct Routing to Microsoft Teams and links to their offerings. 

Microsoft Teams is one of the most powerful tools released by Microsoft in recent years, it focuses on group communication, on intuitive Instant Messaging for conversations that fit seamlessly in with workflow, on document and screen sharing to aid collaboration, and on easy escalation to voice and video calls or conferences when typing a message just won’t do.