Your question is Design Zero-Downtime Redundancy. Take a moment with it on the right.
Talk me through your thinking if you like. When you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes).
How would you design a redundant network topology to ensure zero downtime during a hardware failure?
Explain the topology, redundancy mechanisms, traffic failover behavior, and how you would detect and recover from failures. Address the assumptions, protocols, operational procedures, and tradeoffs involved.