1-6
can configure a re-initialization delay. With this delay configured, a port must wait for the specified
interval before it can initialize LLDP after the LLDP operating mode changes.
Transmitting LLDPDUs
An LLDP-enabled port operating in TxRx mode or Tx mode sends LLDPDUs to its directly connected
devices both periodically and when the local configuration changes. To prevent the network from being
overwhelmed by LLDPDUs during times of frequent local device information change, an interval is
introduced between two successive LLDPDUs.
This interval is shortened to 1 second in either of the following two cases:
z A new neighbor is discovered, in other words, a new LLDPDU is received carrying device
information new to the local device.
z The LLDP operating mode of the port changes from Disable/Rx to TxRx or Tx.
This is the fast sending mechanism of LLDP. This feature sends a specific number of LLDPDUs at the
1-second interval to help LLDP neighbors discover the local device as soon as possible. Then, the
normal LLDPDU transmit interval resumes.
Receiving LLDPDUs
An LLDP-enabled port operating in TxRx mode or Rx mode checks the validity of TLVs carried in every
received LLDPDU. If valid, the information is saved and an aging timer is set for it based on the time to
live (TTL) value in the Time To Live TLV carried in the LLDPDU. If the TTL value is zero, the information
is aged out immediately.
Protocols and Standards
The protocols and standards related to LLDP include:
z IEEE 802.1AB-2005, Station and Media Access Control Connectivity Discovery
z ANSI/TIA-1057, Link Layer Discovery Protocol for Media Endpoint Devices
LLDP Configuration Task List
Complete these tasks to configure LLDP:
Task Remarks
Enabling LLDP Required
Setting the LLDP Operating Mode Optional
Setting the LLDP Re-Initialization Delay Optional
Enabling LLDP Polling Optional
Configuring the Advertisable TLVs Optional
Configuring the Management Address and Its Encoding Format Optional
Setting Other LLDP Parameters Optional
Performing
Basic LLDP
Configuration
Setting an Encapsulation Format for LLDPDUs
Optional
Configuring CDP Compatibility Optional
Configuring LLDP Trapping Optional
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