Cisco Certified Network Associate (CCNA) Practice Exam

For what reasons would a network administrator use Cisco Discovery Protocol (CDP)? (Select two)

1. To obtain VLAN information from directly connected switches

2. To verify the type of cable interconnecting two devices

3. To verify Layer 2 connectivity between two devices when Layer 3 fails

4. To obtain the IP address of a connected device to telnet to it

The correct answer is: To verify Layer 2 connectivity between two devices when Layer 3 fails

A network administrator would use Cisco Discovery Protocol (CDP) primarily to verify Layer 2 connectivity between two devices when Layer 3 fails. CDP operates at Layer 2 of the OSI model, allowing devices to share information about one another directly over the data link layer. This is particularly useful because if there is an issue with Layer 3 (the network layer responsible for IP routing), the administrator can still confirm the physical and logical connections through CDP. By using CDP, admins can gather valuable information such as the device type, capability, and even the interface from which the connection is made, which aids in troubleshooting connectivity issues. Additionally, retrieving VLAN information from directly connected switches is a valid use of CDP, as it allows for the discovery of configurations that are imperative for managing Ethernet segments effectively. This reinforces the administrator's visibility into how devices are interconnected within VLANs and helps streamline network management. The verification of cable types or obtaining IP addresses through CDP, however, is outside the protocol’s designed functionalities. CDP does not provide access to the physical medium's specifications, nor does it serve as a mechanism for obtaining IP addresses directly, since the focus is on sharing device-related information rather than determining Layer 1 conditions or resolving