Which networking technology can be configured on Layer 3 interfaces but not on Layer 2...

NetFlow is a Layer 3 (network layer) protocol that collects and monitors IP traffic flows. It is typically configured on Layer 3 interfaces because it relies on IP information for traffic flow analysis, which is not available on Layer 2 interfaces. Layer 2 interfaces handle frames within the local network, and they don't have IP-related details that NetFlow uses to generate traffic statistics.