Exam 200-310 topic 2 question 203 discussion

View the Exhibit.

You administer the network shown in the topology diagram above. RouterA and HostD are nonCisco devices. RouterMain, SwitchB, PhoneC, and RouterE are
Cisco devices.
Information about which of the following devices will be displayed in the output of the show cdp neighbors command on RouterMain? (Choose two.)

Suggested Answer: BC 🗳️
Section: Design Objectives Explanation

Information about SwitchB and PhoneC will be displayed in the output of the show cdp neighbors command on RouterMain. Cisco Discovery Protocol (CDP) is used to advertise and discover Cisco devices on a local network. CDP is enabled by default on many Cisco devices, but it can be disabled for security purposes.
When CDP is enabled, devices periodically send advertisements out each CDP-enabled interface. These advertisements contain information about the capabilities of the device and are sent to a hardware multicast address. Each directly connected CDP-enabled device receives the broadcast and uses that information to build a CDP table. The CDP table information can be used in conjunction with data gleaned from commandline interface (CLI) output, such as that from the traceroute command, to build a topology map of an existing network.
CDP operates at Layer 2, which is the Data Link layer, of the Open Systems Interconnection (OSI) model. Because it operates at Layer 2, even devices using different Layer 3 protocols can communicate and share information. The type of information collected by CDP includes the host name, IP address, port information, device type, and IOS version of neighboring devices. The following is sample output from the show cdp neighbors command:

The Device ID field indicates the host name, Media Access Control (MAC) address, or serial number of the neighboring device. The Local Intrfce field indicates the interface on the local device. The Holdtme field indicates the amount of time remaining before the CDP advertisement is discarded. The Capability field indicates the type of device:
✑ R -router
✑ S -switch
✑ I -Internet Group Management Protocol (IGMP) device
✑ H -host

T -transparent bridge -

✑ B -sourcerouting bridge
✑ r -repeater
The Platform field indicates the product number of the neighboring device. The Port IDfield indicates the connected interface on the neighboring device.
Information about RouterA and HostD will not be displayed in the output of the show cdp neighbors command on RouterMain, because RouterA and HostD are not Cisco devices. CDP will not display information about non-Cisco devices. However, if Link Layer Discovery Protocol (LLDP) had been used to build a topology map in this scenario and all of the devices supported LLDP, RouterA and HostD might have appeared in the LLDP topology table along with SwitchB and PhoneC.
LLDP is an open-standard network discovery protocol described in the Institute of Electrical and Electronics Engineers (IEEE) 802.1AB standard. LLDP is designed to operate in a multivendor environment and operates in a manner similar to CDP. Most Cisco platforms support both CDP and LLDP.
Information about RouterE will not be displayed in the output of the show cdp neighborscommand on RouterMain, because RouterE is not directly connected to
RouterMain. Although RouterE is a Cisco device, RouterE cannot share information over CDP unless it is directly connected to RouterMain.
Reference:
Cisco: Cisco IOS Configuration Fundamentals Command Reference, Release 12.2: show cdp neighbors