Switch discovery protocols help vSphere administrators to determine which port of the physical switch is connected to a vSphere standard switch or vSphere distributed switch.
vSphere 5.0 and later supports Cisco Discovery Protocol (CDP) and Link Layer Discovery Protocol (LLDP). CDP is available for vSphere standard switches and vSphere distributed switches connected to Cisco physical switches. LLDP is available for vSphere distributed switches version 5.0.0 and later.
When CDP or LLDP is enabled for a particular vSphere distributed switch or vSphere standard switch, you can view properties of the peer physical switch such as device ID, software version, and timeout from the vSphere Web Client.