The Cisco Discovery Protocol (CDP) sure looks simple enough, but there are quite a few details to know for success on the CCNA exam. In your CCNP studies, you’ll be introduced to additional uses for CDP, but for now it’s enough to know that CDP is designed to give you information regarding directly connected Cisco routers and switches.
CDP runs by default between all directly connected Cisco devices. CDP is also a Cisco-proprietary protocol – if the directly connected device is not a Cisco device, you won’t see the information you wanted.
The basic CDP command to display information about the directly connected neighbor is “show cdp neighbor”.
R2#show cdp neighbor
Capability Codes: R – Router, T – Trans Bridge, B – Source Route Bridge
S – Switch, H – Host, I – IGMP, r Repeater
Device ID Local Intrfce Holdtme Capability Platform Port ID
R1 BRI0 167 R 2521 Dialer1
This command is particularly helpful when troubleshooting Cisco switches. Theres...