Neighbour Discovery Protocols - Part 5 ( LLDP-MED ) - :
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LLDP-MED (Link Layer Discovery Protocol-Media Endpoint Discovery)

As a standard and open protocol, LLDP is a good protocol. After the development of LLDP, some of the additional properties needed especially for Voice Over IP (VoIP). So LLDP extended.

The extended version of LLDP is LLDP-MED (Link Layer Discovery Protocol – Media Endpoint Discovery). You can also called this “LLDP for Media Endpoint Devices”.

LLDP enables network discovery between network devices and the endpoint devices like IP Phones, gateways etc.

Link Layer Discovery Protocol-Media Endpoint Discovery, LLDP-MED

Link Layer Discovery Protocol-Media Endpoint Discovery, LLDP-MED

Like LLDP, LLDP-MED is also must be enabled at that end point. In the network different neighbour discovery protocols used at the same time. LLDP-MED is used for its additional advantages. With LLDP -MED, device capabilities can be discovered beside its types. Duplex type and speed, power discovery, location discovery and the device attribute discovery is done with LLDP-MED.

LLDP-MED has three classes that specifies the endpoint’s capabilities. These classes are :

• Class 1 : This LLDP-MED class requires a basic LLDP discovery. Communication controller servers are in this class.
• Class 2 : This LLDP-MED class do not require end user. Voice and Media Gateways, Bridges etc. are in these class.
• Class 3 : This LLDP-MED class is used for the end users. IP Phones, Softphones etc.

LLDP-MED Classes

LLDP-MED Classes


LLDP-MED (Link Layer Discovery Protocol – Media Endpoint Discovery) and CDP (Cisco Discovery Protocol) has some common and different capabilities. Let’s check these common capabilities one by one.



Device Type Discover : It shows the type of the device. IP Phone, switch, hub etc.

Device Capability Discover : It shows the specific capabilities of the device. Port informations, interface availabilities etc.

Speed Discover : The network speed, bandwith.

Duplex Discover : Half Duplex or Full Duplex.

VLAN Configuration Support : Any information about the VLANs that device has.

Network Policy Control : The control of the application policies of device. VLAN is also included. LLDP-MED provides better network policy control than CDP (Cisco Discovery Protocol)

Location Discover : Makes the device avare of its location. LLDP-MED porvides more format than CDP.

Power Discover :
Power information of the device. Especially used with Power over Ethernet (PoE). CDP provides two way power discover. This is not a capability in LLDP-MED.

Device Attribute Discover : Discovering the specific attributes like serial number, model, etc.

Phone Trust Extension : Extending the trust boundary to the IP Phone and with this, packets coming from the PC port of the switch is trusted.

In this article, we have talked about the extended version of LLDP, LLDP-MED. I hope it will be a beneficial article for you. Keep on, ;)

Neighbour Discovery Protocols – Part 1
Neighbour Discovery Protocols – Part 2 ( LLDP )
Neighbour Discovery Protocols – Part 3 ( CDP )
Neighbour Discovery Protocols – Part 4 ( CDP Configuration Example )
Neighbour Discovery Protocols – Part 5 ( LLDP-MED )
Neighbour Discovery Protocols – Part 6 ( LLDP Cisco Configuration)

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About the Author
Gokhan Kosem is a telecommunation and network engineer. His ambition to IP networks and end-to-end system installation made him to prepare this web-site. By sharing his experiences about various networking protocols beside different system installation experiences and Cisco, Juniper, Alcatel-Lucent devices configurations, he is aimed to be helpful for his collegues in all over the world. He is currently lives in Istanbul, Turkey.

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