When you arrive at an unfamiliar network, or a diagram is out of date, discovery protocols tell you what is plugged into each port. Cisco Discovery Protocol (CDP) and Link Layer Discovery Protocol (LLDP) both have devices periodically advertise information about themselves to their directly connected neighbours. They run at Layer 2, so they work even before IP is configured, and their messages are never forwarded past the immediate neighbour. That makes them ideal for building a map one hop at a time, and for confirming that a cable really lands where the documentation says it does.
Keep reading for free
Create a free StudyToCert account to read the rest of this lesson: 7 more sections, 6 key terms, a real-world example, an exam tip and self-check questions. Every lesson, lab and practice test is free with an account.