Basic Administration Protocols
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Instruction Manual - NXA-ENET8-POE+
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.
The following table lists the options on this page:
Administration - LLDP Options
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 increase the probability that multiple,
rather than single changes, are reported in each transmission.
This attribute must comply with the rule: (4 * Delay Interval) <=Transmission Interval
Reinitialization Delay
Configures the delay before attempting to re-initialize after LLDP ports are disabled or the link goes
down. (Range: 1-10 seconds; Default: 2 seconds)
When LLDP is re-initialized on a port, all information in the remote systems LLDP MIB associated
with this port is deleted.
Notification Interval
Configures the allowed interval for sending SNMP notifications about LLDP MIB changes. (Range:
5-3600 seconds; Default: 5 seconds)
This parameter only applies to SNMP applications which use data stored in the LLDP MIB for
network monitoring or management.
Information about changes in LLDP neighbors that occur between SNMP notifications is not
transmitted. Only state changes that exist at the time of a notification are included in the
transmission. An SNMP agent should therefore periodically check the value of
lldpStatsRemTableLastChangeTime to detect any lldpRemTablesChange notification-events missed
due to throttling or transmission loss.
MED Fast Start Count
Configures the amount of LLDP MED Fast Start LLDPDUs to transmit during the activation process
of the LLDP-MED Fast Start mechanism. (Range: 1-10 packets; Default: 4 packets)
The MED Fast Start Count parameter is part of the timer which ensures that the LLDP-MED Fast
Start mechanism is active for the port. LLDP-MED Fast Start is critical to the timely startup of LLDP,
and therefore integral to the rapid availability of Emergency Call Service.