Start with physical dependencies
Different carrier names do not prove diverse physical routes. Ask about the building entrance, local loop, conduit and upstream facilities. Where evidence is limited, record the uncertainty as part of the risk decision.
Check the complete failure domain
A second circuit can still depend on the same power, edge device or internal cabling. Consider equipment redundancy, power protection and how a circuit failure is detected.
Choose a backup for its purpose
5G, fixed wireless and low Earth orbit satellite can provide alternatives to terrestrial access. Validate coverage, installation constraints, data limits and application behavior instead of assuming every backup can carry every workload.
Test the actual business outcome
Measure the interruption experienced by critical applications during failover and recovery. SD-WAN path selection does not guarantee that existing sessions survive an address or route change.
Further reading
Industry context: Managed SD-WAN · SASE architecture. These references explain technology concepts and do not imply a commercial partnership.