At which layer of the OSI model does the protocol that provides the information that is displayed by the show cdp neighbors command operate?

At which layer of the OSI model does the protocol that provides the information that is displayed by the show cdp neighbors command operate?
A . application
B . transport
C . network
D . physical
E . data link

Answer: E

Explanation:

CDP is a device discovery protocol that runs over Layer 2 (the data link layer) on all Cisco- manufactured devices (routers, bridges, access servers, and switches) and allows network management applications to discover Cisco devices that are neighbors of already known devices.With CDP, network management applications can learn the device type and the Simple Network Management Protocol (SNMP) agent address of neighboring devices running lower-layer, transparent protocols.