Web Management Guide-R06

Chapter 13 | Basic Administration Protocols
Link Layer Discovery Protocol
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Link Layer Discovery Protocol
Link Layer Discovery Protocol (LLDP) is used to discover basic information about
neighboring devices on the local broadcast domain. LLDP is a Layer 2 protocol that
uses periodic broadcasts to advertise information about the sending device.
Advertised information is represented in Type Length Value (TLV) format according
to the IEEE 802.1AB standard, and can include details such as device identification,
capabilities and configuration settings. LLDP also defines how to store and
maintain information gathered about the neighboring network nodes it discovers.
Link Layer Discovery Protocol - Media Endpoint Discovery (LLDP-MED) is an
extension of LLDP intended for managing endpoint devices such as Voice over IP
phones and network switches. The LLDP-MED TLVs advertise information such as
network policy, power, inventory, and device location details. LLDP and LLDP-MED
information can be used by SNMP applications to simplify troubleshooting,
enhance network management, and maintain an accurate network topology.
Setting LLDP
Timing Attributes
Use the Administration > LLDP (Configure Global) page to set attributes for general
functions such as globally enabling LLDP on the switch, setting the message
ageout time, and setting the frequency for broadcasting general advertisements or
reports about changes in the LLDP MIB.
Parameters
These parameters are displayed:
◆ LLDP – Enables LLDP globally on the switch. (Default: Enabled)
◆ Transmission Interval – Configures the periodic transmit interval for LLDP
advertisements. (Range: 5-32768 seconds; Default: 30 seconds)
◆ Hold Time Multiplier – Configures the time-to-live (TTL) value sent in LLDP
advertisements as shown in the formula below. (Range: 2-10; Default: 4)
The time-to-live tells the receiving LLDP agent how long to retain all
information pertaining to the sending LLDP agent if it does not transmit
updates in a timely manner.
TTL in seconds is based on the following rule:
minimum value ((Transmission Interval * Holdtime Multiplier), or  65535)
Therefore, the default TTL is 4*30 = 120 seconds.
◆ Delay Interval – Configures a delay between the successive transmission of
advertisements initiated by a change in local LLDP MIB variables.
(Range: 1-8192 seconds; Default: 2 seconds)
The transmit delay is used to prevent a series of successive LLDP transmissions
during a short period of rapid changes in local LLDP MIB objects, and to