Cisco CCNA (200-301)Network FundamentalsHard
A network engineer is troubleshooting a connection between two routers. The 'show cdp neighbors detail' command output shows that RouterA's local interface GigabitEthernet0/1 is connected to RouterB's remote interface GigabitEthernet0/0. What information does CDP provide about the remote device in this scenario?
- AThe routing table of RouterB.
- BThe Cisco IOS version running on RouterB.
- CThe MAC address of RouterB's GigabitEthernet0/0 interface.
- DThe IP address of RouterB's GigabitEthernet0/0 interface.
Show answer & explanationAnswer & explanation
Correct answer: B. The Cisco IOS version running on RouterB.
Cisco Discovery Protocol (CDP) is a proprietary Layer 2 protocol that gathers information about directly connected Cisco devices. The 'show cdp neighbors detail' command provides detailed information including device ID, local interface, remote interface, platform, capabilities, and the Cisco IOS version of the neighboring device.
Why the other options are wrong
- A. CDP is a Layer 2 protocol and does not share routing table information; routing protocols (Layer 3) are used for that purpose.
- C. CDP operates at Layer 2, but its primary function is discovery of device capabilities and platform, not displaying the MAC address of the remote interface in the 'detail' output.
- D. CDP does not typically provide the IP address of the remote interface in its standard output, though it can show management IP addresses if configured.
Cisco Discovery Protocol (CDP)
CDP is a Cisco proprietary Layer 2 protocol used to discover information about directly connected Cisco devices, such as device type, IOS version, capabilities, and interface information.
- Runs on all Cisco devices by default.
- Operates at Layer 2 (data link layer).
- Useful for network mapping and troubleshooting.
- Provides device ID, platform, capabilities, and IOS version.
Memory trick: CDP is a detective, finding clues about its direct neighbors.