10 Session border controllers
Pro tips
• Certification means that SBC software is supported with Direct Routing. You still configure the vendor release you run.
• AudioCodes, Ribbon, Oracle, and Cisco CUBE are families. The support path starts with that vendor's guide.
• Failover is a second gateway on the voice route that you have rehearsed, not a hostname you hope is warm.
Interview traps
• Opening a Microsoft case for a firmware or DSP fault the vendor owns.
• Cloning the London trunk to Manchester and leaving the certificate name or the OPTIONS target unchanged.
Cheat sheet
Certified list -> the release you actually run
Pair primary and secondary, both on the route
Firewall current Teams ranges, both directions
Rehearse fail the primary before the site depends on it
Vendor first when the symptom is on the SBC itself
Facts in the long lessons were checked 14 October 2026. This sheet is a memory aid.