When configuring server flows for SIP trunking in a Microsoft Teams deployment, you must configure trunks for the PSTN and server flows for the Microsoft Teams SIP proxy. By configuring the SIP trunks and server flows, you create routing paths between the PSTN and the Microsoft Teams SIP proxy.

For Microsoft Teams to route across multiple Microsoft Teams servers, the call servers must be configured with the following FQDN names and have priority load balancing set:

Add the FQDNs of the three call servers as priority 1, 2, and 3, with the appropriate SIP server profile type corresponding to Microsoft Teams. The priority one Microsoft Teams SIP server, sip.pstnhub.microsoft.com, is always tried first. If the priority one server is not in good health due to heartbeat failure in Options, the priority two Microsoft Teams server, sip2.pstnhub.microsoft.com is tried next. If that server is not in good health, the priority three Microsoft Teams server, sip3.pstnhub.microsoft.com, is tried next. This mechanism provides in Microsoft Teams failover and geo-redundancy.

By default, the URI group is defined as *, but it can be defined with any other value as required by a Microsoft Teams specific URI group profile if a specific number pattern is allowed for Direct Routing.