MS-700 Manage Meetings and Calling Practice Question
You are a Teams administrator for a large organization that uses Microsoft Teams Phone with Direct Routing. The company has a Survivable Branch Appliance (SBA) deployed at a branch office. During a recent WAN outage, users at the branch office were unable to make or receive PSTN calls even though the SBA was online. You need to ensure that during future WAN outages, branch users can continue to make and receive PSTN calls. What should you configure?
⚠ Common exam trap
Watch out — candidates often confuse high availability of the SBC with branch survivability, which specifically requires the SBA to have a local PSTN gateway and host users during an outage.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure the SBA to use a local PSTN gateway and register users to the SBA for failover.
To ensure branch office users can continue to make and receive PSTN calls during a WAN outage, the Survivable Branch Appliance (SBA) must be configured with a local PSTN gateway and the branch users must be homed on the SBA for failover. This allows the SBA to register users locally and route calls through the local gateway when the connection to Microsoft 365 is unavailable, providing seamless PSTN access.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Assign the branch users a Calling Plan license as a backup to Direct Routing.
Why it's wrong here
Calling Plans provide PSTN connectivity through Microsoft's cloud, but they require an internet connection to Microsoft 365. During a WAN outage, the branch office loses connectivity to Microsoft 365, so Calling Plans would not work. The SBA is specifically designed to provide local PSTN fallback when the WAN is down. Adding Calling Plans would not solve the outage scenario and would incur unnecessary costs.
- ✓
Configure the SBA to use a local PSTN gateway and register users to the SBA for failover.
Why this is correct
A Survivable Branch Appliance (SBA) is designed to provide local PSTN connectivity when the connection to Microsoft 365 is lost. To enable this, the SBA must have a local PSTN gateway (or SIP trunk) and the branch users must be homed on the SBA for failover. During a WAN outage, the SBA registers the users locally and routes their calls through the local gateway, ensuring continued PSTN access. This configuration is essential for branch survivability.
- ✗
Enable Media Bypass on the SBA and update the network topology.
Why it's wrong here
Media Bypass reduces latency by keeping media on the local network, but it does not provide PSTN call survivability during a WAN outage. The SBA itself is responsible for providing fallback PSTN connectivity. Media Bypass requires the SBA to have direct connectivity to the session border controller (SBC), but if the WAN is down, the SBA must handle calls locally. This option does not address the need for local call routing and failover.
- ✗
Deploy a second SBC at the branch office and configure it for high availability.
Why it's wrong here
A second SBC improves redundancy for the SIP trunk connection to Microsoft 365, but it does not provide local survivability during a WAN outage. The SBA is the component that enables local call routing when the branch loses connectivity to the cloud. Adding another SBC would not help if the WAN link is down, because the SBC still needs to communicate with Microsoft 365 for call signaling. This option misidentifies the role of the SBA.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Microsoft exam blueprint
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