Network telemetry is a technology for gaining network insight and facilitating efficient and automated network management. It encompasses various techniques for remote data generation, collection, correlation, and consumption1. Network telemetry can be used for various purposes, such as network performance monitoring, security analysis, troubleshooting, and optimization. One of the applications of network telemetry is Layer 2 device discovery, which allows network operators to discover and map the physical topology of the network, including switches, routers, hosts, and links. Layer 2 device discovery can be achieved by using protocols such as Link Layer Discovery Protocol (LLDP) or Cisco Discovery Protocol (CDP), which enable network devices to advertise their identity, capabilities, and neighbors to other devices on the same network segment. To enable Layer 2 device discovery, network telemetry must be enabled on the network devices, so that they can send and receive LLDP or CDP packets. This feature requires network telemetry to be enabled, because without it, the network devices would not be able to exchange information about their topology and configuration. Therefore, the correct answer is C. Layer 2 device discovery. References: 1: RFC 9232: Network Telemetry Framework - Internet Engineering Task Force