Which Cisco proprietary protocol is used to discover information about directly connected Cisco devices?
Correct Answer: A
Detailed Explanation: Cisco Discovery Protocol (CDP) is a Cisco proprietary Layer 2 protocol designed for network discovery. It is used by Cisco devices (such as routers, switches, and IP phones) to advertise their identity, capabilities, and neighbors on a directly connected network segment. Purpose of CDP: CDP operates at the data link layer and enables devices to share critical information with adjacent Cisco devices. This includes details such as device identifiers, IP addresses, software versions, and port identifiers. Network administrators can use CDP to quickly map out network topologies, which simplifies troubleshooting, documentation, and configuration management. How CDP Works: Each Cisco device configured with CDP periodically sends out CDP advertisements (typically every 60 seconds) on all enabled interfaces. These advertisements are multicast frames that are sent to a reserved MAC address. Devices receiving these advertisements store the information in a local cache. Administrators can then view this information using commands like: show cdp neighbors This command lists neighboring devices along with details like the port connections and device type. For more detailed information, the command: show cdp neighbors detail can be used, which provides a comprehensive view including IP addresses and software versions. Benefits and Applications: Topology Discovery: CDP helps network engineers visualize the network layout. Knowing which devices are interconnected simplifies both planning and troubleshooting. Configuration Assistance: When deploying new devices or upgrading firmware, CDP information can verify that the devices are correctly connected. Interoperability: Although CDP is Cisco-specific, similar functions are provided by LLDP (Link Layer Discovery Protocol), which is an IEEE standard. However, LLDP is vendor-neutral and not always enabled by default on Cisco devices. Troubleshooting: In complex networks, CDP can quickly identify misconfigurations or physical connectivity issues by showing unexpected or missing neighbors. Comparing to Other Options: LLDP: While LLDP (Option B) is a similar protocol used for network discovery, it is an open standard and not proprietary to Cisco. Many Cisco devices support both CDP and LLDP, but CDP is specific to Cisco environments. SNMP (Option C): SNMP is used for network management and monitoring rather than neighbor discovery. It gathers performance and status information from network devices. NETCONF (Option D): NETCONF is a network management protocol that provides mechanisms for installing, manipulating, and deleting the configuration of network devices. It is not used for discovering directly connected devices. Conclusion: For Cisco networks, CDP is the primary tool for discovering adjacent Cisco devices and collecting essential network information. It simplifies network management by providing an automated means of topology discovery and detailed device information. This makes CDP (Option A) the correct answer, as it is specifically designed for this purpose and is widely utilized by Cisco administrators.
This CCNA practice question helps students prepare for Cisco networking certification exams by testing knowledge of network fundamentals, routing, switching, and network security concepts.