08 Emergency, LBR, survivability
Pro tips
• Dynamic emergency calling walks trusted IP, network site, subnet, and civic address. A VPN pool is often not a dispatchable location.
• On Direct Routing you choose whether the SBC or Microsoft routes the emergency call. Say which hop you configured.
• A Survivable Branch Appliance keeps a limited set of calls up when the path to Microsoft 365 fails. It does not replace the SBC.
Interview traps
• Placing a real emergency call to test a lab. Use the matcher and a test policy.
• Treating location-based routing and emergency location as the same feature. They share sites and do different jobs.
Cheat sheet
Trusted IP -> site -> subnet -> civic address
Emergency route: Microsoft or your SBC, on purpose
LBR: selected PSTN stays on the local gateway
SBA: some branch calling during a WAN loss
SBA scope is smaller than normal Teams Phone
Facts in the long lessons were checked 14 October 2026. This sheet is a memory aid.