What is the primary purpose of the LLDP-MED?

A.
It learns the MAC address of the peer device.

B.
It communicates the provisioned VLAN ID to the peer device.

C.
It eliminates the need for a spanning tree.

D.
It authenticates the peer device.

Explanation:
Juniper Networks EX Series Ethernet Switches use Link Layer Discovery Protocol (LLDP) and Link Layer Discovery ProtocolMedia Endpoint Discovery (LLDP-MED) to learn and distribute device information on network links. The information allows the switch to quickly identify a variety of devices, resulting in a LAN that interoperates smoothly and efficiently.

LLDP-capable devices transmit information in type, length, and value (TLV) messages to neighbor devices. Device information can include specifics, such as chassis and port identification and system name and system capabilities. The TLVs leverage this information from parameters that have already been configured in the Juniper Networks Junos operating system (Junos OS).

LLDP-MED goes one step further, exchanging IP-telephony messages between the switch and the IP telephone. These TLV messages provide detailed information on PoE policy. The PoE Management TLVs let the switch ports advertise the power level and power priority needed.

When you enable LLDP-MED autonegotiation on an EX Series switch, the autonegotiation bit in the LLDP-MED packet is set to not-supported, which might cause IP phones to discard LLDP-MED packets received from the switch.