Explanation/Reference:
Section: Design Methodologies Explanation
Explanation:
Cisco Discovery Protocol (CDP) is a Cisco-proprietary protocol used by Cisco devices to detect neighboring Cisco devices. For example, Cisco switches use CDP to determine whether an attached Voice over IP (VoIP) phone is manufactured by Cisco or by a third party. 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.
CDP packets are broadcast from a CDPenabled device on a multicast address. Each directly connected CDPenabled device receives the broadcast and uses that information to build a CDP table. Detailed information about neighboring CDP devices can be viewed in IOS by issuing the show cdp neighbor detail command in global configuration mode. The following abbreviated sample output shows information obtained from CDP about the IP phone named SEP00123456789A:

Link Layer Detection Protocol (LLDP), not CDP, is a standard protocol that detects neighboring devices of any type. Cisco devices also support LLDP. LLDP can be used in a heterogeneous network to enable Cisco devices to detect non-Cisco devices and vice versa. LLDP, which is enabled by default, can be disabled globally by issuing the no lldp run command. You can reenable LLDP by issuing the lldp run command.
CDP is not a protocol used to power IP devices over Ethernet, although an IP phone can provide Power over Ethernet (PoE) requirements to a switch by using CDP. A Catalyst switch can provide power to both Cisco and non-Cisco IP phones that support either the 802.3af standard method or the Cisco prestandard method of PoE. For a Catalyst switch to successfully power an IP phone, both the switch and the IP phone must support the same PoE method. After a common PoE method is determined, CDP messages sent between Catalyst switches and Cisco IP phones can further refine the amount of power allocated to each device.
Reference:
CCDA 200-310 Official Cert Guide, Chapter 15, CDP, p. 629
Cisco: Catalyst 3750 Switch Software Configuration Guide, 12.2(40)SE: Configuring CDP