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| Configuring the Switch
Configuring Link Layer Discovery Protocol
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CONFIGURING 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.
PARAMETERS
The following parameters are displayed on the LLDP Configuration page:
LLDP Timing Attributes
◆ Tx Interval – Configures the periodic transmit interval for LLDP
advertisements. (Range: 5-32768 seconds; Default: 30 seconds)
This attribute must comply with the following rule:
(Transmission Interval * Transmission Hold Time) ≤ 65536,
and Transmission Interval ≥ (4 * Transmission Delay)
◆ Tx Hold – Configures the time-to-live (TTL) value sent in LLDP
advertisements as shown in the formula below. (Range: 2-10;
Default: 3)
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:
(Transmission Interval * Transmission Hold Time) ≤ 65536.
Therefore, the default TTL is 30*3 = 90 seconds.
◆ Tx Delay – 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 * Transmission Delay) ≤ Tra ns missio n Inte rva l
◆ Tx Reinit – 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
system’s LLDP MIB associated with this port is deleted.
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