From the course: CCNP Switching (300-115) Cert Prep: 1 Layer 2 Technologies

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Discovering connected devices

Discovering connected devices

- [Instructor] Device discovery is often invaluable for both troubleshooting, as well as some services like VoIP phones. If I am forced to work on a foreign network that has no documentation, I generally begin by connecting to the core switch, then doing neighbor discovery, then hop from device to device, mapping my way through. Cisco Discovery Protocol, or CDP, was devised to be an automatic method to advertise a devices information to neighboring devices, be them switch or router. Though CDP is a Cisco proprietary protocol, many manufacturers support it. CDP is sent one-way via Layer 2. The one-way nature simply means there is no acknowledgement. By default, advertisements are sent every 60 seconds out of every active interface. The command used to display neighbors is show cdp neighbor. This command will give the ID your hostname of the neighbor, the interface the device uses to connect to them, capabilities of neighbor, platform type, and the port the neighbor uses to connect to…

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