Which feature must be configured to allow packet capture over a Layer 3 infrastructure?

ERSPAN (Encapsulated Remote Switched Port Analyzer) is the correct feature because it allows for the capture of traffic from source ports or VLANs and encapsulates it into a GRE tunnel. This encapsulation enables the captured traffic to be sent across a Layer 3 network to a destination, such as a network analyzer. RSPAN (Remote Switched Port Analyzer) is incorrect because it operates only within a single Layer 2 domain and uses a dedicated VLAN to carry monitored traffic, making it unsuitable for Layer 3 infrastructure. VSPAN and IPSPAN are not standard Cisco features for this purpose.