All slides are customized by Engr. Vernon Degala. For educational purposes only.All slides are customized by Engr. Vernon Degala. For educational purposes only.
Module 4: Learning about Devices
inspired by Cisco Networking Academy
Computer Networks and Security
CCNA 2: Routers and Routing Basics
ORIGINAL COPY
All slides are customized by Engr. Vernon Degala. For educational purposes only.
Cisco Discovery Protocol (CDP)
•Cisco Discovery Protocol (CDP) is a Layer 2 protocol that connects lower physical media
and upper network layer protocols
•CDP is used to obtain information about neighboring devices, such as the types of
devices connected
•CDP is media and protocol independent, and runs on all Cisco equipment
•When a Cisco device boots up, CDP starts up automatically and allows the device to
detect neighboring devices that are also running CDP
•It runs over the data link layer and allows two systems to learn about each other
•Each device configured for CDP sends periodic messages, known as advertisements, to
multiple routers.
Each device advertises:
•at least one address at which it can receive Simple Network Management Protocol (SNMP) messages.
•“time-to-live” or holdtime information, indicating the length of time that receiving devices should hold CDP
information before discarding it.
•each device also listens to periodic CDP messages sent by others in order to learn about neighboring devices.
