Link Layer Discovery Protocol Media Endpoint Discovery (MED) is an extension to LLDP that is published as standard ANSI/TIA-1057. LLDP MED TLVs advertise and receive information for endpoint devices, which can include powered device (PD) information. Some TLVs are advertised by the switch, and some are advertised by the endpoint device.
![]() LLDP MED TLVs
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You must enable the LLDP-MED capabilities TLV for advertising before you configure any other LLDP MED TLVs for advertising. Likewise, when disabling LLDP MED TLV advertisement, you can disable the LLDP-MED capabilities TLV only after you have disabled advertisement for all other LLDP MED TLVs.
After the LLDP-MED capabilities TLV is configured for advertising, the switch can receive LLDP MED TLVs from endpoints; you do not have to configure the switch to receive individual TLVs.
The switch advertises LLDP MED TLVs only after the switch receives an LLDP MED TLV from an endpoint, and the switch only advertises on ports from which an LLDP MED TLV has been received. This approach prevents the switch from advertising LLDP MED TLVs to another switch, and it prevents the wasted bandwidth and processing resources that would otherwise occur.
The LLDP MED protocol extension introduces a new feature called MED fast start, which is automatically enabled when the LLDP MED capabilities TLV is configured for advertisement.
When a new LLDP MED-capable endpoint is detected, the switch advertises the configured LLDP MED TLVs every one second for the configured number of times (called the repeat count). This speeds up the initial exchange of LLDP MED capabilities. After the repeat count is reached, the LLDP MED TLVs are advertised at the configured interval.
Note
The fast-start feature is automatically enabled, at the default level of 3, when you enable the LLDP MED capabilities TLV on the port.