Hi Eric, an LLDP frame is essentially made up of three types of TLVs:
Mandatory TLVs: (Chassis ID, port ID, TTL and End LLDPDU) As long as a system is transmitting an LLDP frame, it MUSt contain these TLVs. By running the enable lldp command, these TLVs are automatically advertised. Optional TLVs: (Port description, systems name and description, management address and system capabilities). As the name states, these aren't required, but can be advertised in addition to the above TLVs. They can be individually added using the configure lldp advertise if configured globally for all ports OR configure lldp port advertise if configured on a per-port basis Custom TLVs: Over the years the original LLDP standard has undergone some enhancements by either standards organizations ( i.e. ITU or the IEEE themselves (i.e. LLDP-MED, DCBX) or via vendors like Avaya (i.e.e Ayava TLVs for Extreme). All these customizations are bundled into what we simply call vendor specific attributes. The reason for this is, if you took a packet capture of the LLDP packet, you'll noticed that each of these custom TLVs will have the organization that developed the TLV at the beginning of the TLV (i.e IEEE 802.3 Power Via MDI, Media (TIA TR-41) Committee, Avaya). These would be configured via the configure lldp port advertise vendor specific
I hope this answers your question.
