Explanation/Reference:
Section: Design Methodologies Explanation
Explanation:
The show cdp neighbors command will display the directly connected Cisco devices that are sending Cisco Discovery Protocol (CDP) updates; the directly connected devices in this case are RouterA and SwitchB. The port ID of the sending device will be displayed by the show cdp neighbors command.
Therefore, the show cdp neighbors command will show which port on SwitchB and which interface on RouterA connect to SwitchA. CDP is used to collect information about neighboring Cisco devices and is enabled by default. Because CDP operates at the Data Link layer, which is Layer 2 of the Open Systems Interconnection (OSI) model, CDP is not dependent on any particular Layer 3 protocol addressing, such as IP addressing. Therefore, if CDP information is not being exchanged between devices, you should check for Physical layer and Data Link layer connectivity problems. CDP is enabled by default on Cisco devices.
You can globally disable CDP by issuing the no cdp run command in global configuration mode. You can disable CDP on a perinterface basis by issuing the no cdp enable command in interface configuration mode.
The show cdp neighbors detail command will not show information for all of the Cisco devices on the network. The only devices that will send CDP information are the directly connected devices.
The show cdp neighbors detail command will not display all of RouterA's IP addresses. Updates sent from RouterA and received by SwitchA will include only the IP address of the port that sent the update.
The show cdp neighbors detail command will not show all of the IP addresses of hosts on the LAN. Hosts do not send CDP information? only directly connected Cisco devices send CDP updates.
Reference:
CCDA 200-310 Official Cert Guide, Chapter 15, CDP, p. 629
Cisco: Cisco IOS Configuration Fundamentals Command Reference, Release 12.2: show cdp neighbors