How to configure unassigned phone numbers in Microsoft Teams?

This blog post is about how you can configure unassigned numbers in Microsoft Teams. Since some time by now you can configure unassigned phone numbers in Microsoft Teams for pstn calling. The good thing is that you can do it either via Teams Admin Center or Teams Shell. The ability to manage unassigned numbers in Teams Admin Center was added not that long ago.

Recap – What are unassigned numbers?

Unassigned numbers are phone numbers which you own but do not use at the moment. This often happens in case you have a range of phone numbers for your company, e.g. +49 711 1234 – 000 to -999 but not all of these are assigned to users, phone services or legacy phone endpoints like analog phones.

Recap – What does Microsoft Teams’ unassigned number feature offer?

The unassigned number feature provides the ability that you – as a Teams Voice admin – can configure the handling of unassigned number. This works for single numbers or a range of numbers. I personally prefer to set this up always for a complete number range, e.g. from +49 711 1234 – 000 to -999.

If numbers are assigned the unassigned number feature does not kick in and does not interfere with assigned numbers. It is only applied in case a phone number of this range is called and is really unassigned, does not have any user or service behind.

Please also note, that if you have some special co-existence or migration configuration you might cannot use this, e.g. Teams Direct Routing with a PSTN sip trunk attached to a SBC and the Teams phone system’s sip trunk and a PBX’s sip trunk behind the SBC while incoming calls are routed to both, the Teams Phone System and PBX, in sequence. Depending on your configuration on the SBC it might be not a good idea to set up unassigned numbers in Teams Phone System if the SBC requires a “404 Not Found” from the Teams Phone System to try to route it to the PBX. This will not work any further if you configure the unassigned number feature for the complete range.

Configure unassigned numbers with Teams Shell

In February 2022 I wrote a post which describes the way to do this using Teams Shell which still is valid. For details checkout my previous post on the matter: Unassigned Numbers in Microsoft Teams Phone System –

Configure unassigned numbers in Teams Admin Center

  • Open Teams Admin Center
  • Go to the Voice section
  • Open the Phone numbers area
  • Click on the Routing rules tab
  • Click on Add a new rule to start
  • Click Save to apply your configuration
  • Give the backend some time to process and apply the change
  • Test the number using the built-in test function or call a unassigned number from externally using another phone, e.g. your mobile phone
  • Add further numbers/ranges as needed for other sites

Additional resources

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