Cisco Discovery Protocol (CDP)/Link Layer Discovery Protocol (LLDP)
CDP is a Cisco proprietary layer 2 protocol used between directly connected devices. LLDP is a vendor neutral IEEE standard (IEEE 802.1AB) to perform similar functions.
Cisco devices send CDP announcements to the multicast destination address 01-00-0c-cc-cc-cc every 60 seconds by default. Each Cisco device that supports CDP stores the information received from other devices in a table that can be viewed using the show cdp neighbors command. By default information is aged out of the table after 180 seconds unless refreshed.
Cisco wired IP phones perform an intelligent exchange of information between the phone and the
switchport it is plugged into using Cisco Discovery Protocol (CDP). When the switch discovers a Cisco
IP phone, it can extend QoS trust to it dynamically. CDP can be enabled on Cisco wireless phones via Communications Manager.
Cisco recommends that you disable Cisco Discovery Protocol on the controller and access point when connected to non-Cisco switches as CDP is unsupported on non-Cisco switches and network elements.
By default, CDP is disabled on radio interfaces on indoor (nonindoor mesh) access points.
LLDP information is sent by devices from each of their interfaces at a fixed interval, to a series of multicast addresses. Information is stored and can be queried via SNMP.
If an AP is configured for DHCP, then you can use CDP/LLDP to find out what IP address it has been given by showing the CDP neighbours on the switch to which the AP is connected.