An application on Compute Engine must: map multiple reserved external IP addresses to a single instance and process ESP traffic. What should you do?

The correct approach is to create a target instance and a protocol forwarding rule for each reserved external IP. Target instances are designed for handling specific protocols like ESP (Encapsulating Security Payload) and allow you to forward traffic directly to a single VM instance. Protocol forwarding rules then map the external IP addresses to this target instance. Creating a target pool and protocol forwarding rules is incorrect because target pools are typically used with load balancers for distributing traffic across multiple instances, not for direct, protocol-specific forwarding to a single instance. Creating a backend service and an external network load balancer is also incorrect as load balancers distribute traffic, and while they can handle external IPs, they are not the direct mechanism for forwarding ESP to a single instance. Changing the instance's network interface external IP to Ephemeral and adding multiple external IPs to the instance is incorrect because instances can only have one primary external IP per network interface, and this method doesn't address the requirement for ESP traffic forwarding.