Which of the following statements correctly describe differences between Cisco Discovery Protocol (CDP) and Link Layer Discovery Protocol (LLDP)? (Select all that apply.)
Correct Answer: A,B,C
Detailed Explanation: Device discovery protocols play an essential role in modern networks by allowing network devices to advertise information about themselves to directly connected neighbors. Two common protocols for this purpose are Cisco Discovery Protocol (CDP) and Link Layer Discovery Protocol (LLDP). A. Proprietary vs. Standard: CDP is a Cisco proprietary protocol. It is designed and implemented by Cisco and is used primarily to exchange information among Cisco devices. In contrast, LLDP is defined by the IEEE (802.1AB) and is a vendor-neutral protocol. This standardization means that LLDP is widely supported by devices from multiple vendors, making it a preferred choice in heterogeneous networks. B. Multi-Vendor Environment: Because LLDP is an open standard, it can be implemented on equipment from various vendors. This interoperability is important in networks that do not exclusively use Cisco devices. CDP, on the other hand, is mostly useful in environments that are entirely Cisco-based, as non-Cisco devices may not support or properly interpret CDP messages. C. Functional Capabilities: Both CDP and LLDP operate at the data link layer (Layer 2) and serve to advertise information such as device identifiers, port information, and IP addresses. However, LLDP has been extended in various ways. For example, LLDP-MED (Media Endpoint Discovery) provides additional capabilities, including support for Power over Ethernet (PoE) management, which is useful for VoIP phones and other devices that draw power over Ethernet. This added functionality makes LLDP a robust tool in modern, diverse network environments. D. Security and Encryption: Neither CDP nor LLDP inherently provides encryption for the discovery information they exchange. The protocols are designed for basic neighbor discovery and do not include built-in mechanisms for securing the data against eavesdropping. While network security can be enhanced by other measures (such as securing management traffic using SSH), the discovery protocols themselves transmit information in clear text. Therefore, Option D is incorrect. Practical Considerations: Network administrators use these protocols to automatically learn about the network topology, identify device connections, and assist in troubleshooting physical connectivity issues. The choice between CDP and LLDP often depends on the network’s vendor composition and the specific management needs. In Cisco-only environments, CDP might be used by default, but in mixed environments or where additional features are needed, LLDP is preferred. Conclusion: The differences between CDP and LLDP are best summarized by noting that CDP is Cisco proprietary while LLDP is an IEEE standard (Option A), LLDP is suitable for multi-vendor environments (Option B), and although both advertise similar information at Layer 2, LLDP supports extended capabilities such as PoE management (Option C). Option D is incorrect because neither protocol provides encryption by default. Understanding these differences is essential for proper network discovery and management in varied environments.
This CCNA practice question helps students prepare for Cisco networking certification exams by testing knowledge of network fundamentals, routing, switching, and network security concepts.