Install guide

Link Layer Discovery Protocol (LLDP) 5
Transmission
When LLDP transmission is enabled, the LLDP agent advertises information
about your switch to neighbours at regular, user-configured intervals.
Each transmitted LLDPDU contains the mandatory TLVs, and any optional
TLVs that you have enabled. See “Type Length Values” on page 3 for more
information about TLVs. Or, see “Configuring LLDP” on page 8 to find out
how to configure the TLVs that are advertised on your switch.
When LLDP transmission is disabled, one of two scenarios occurs. If
transmission is disabled:
■ because you have disabled a port using an LLDP command, then the LLDP
agent transmits a single ‘shutdown’ LLDPDU with a Time-To-Live (TTL)
TLV that has a value of "0". This tells any remote neighbouring devices to
remove the information associated with your switch from their remote
systems MIB.
■ for any other reason, for example you have disabled the port using disable
switch port, then the LLDP agent does not send a shutdown LLDPDU.
Note that LLDP does not transmit LLDPDUs on switch ports that are untagged
members of any VLAN other than the default VLAN (vlan1)
Transmission delay
timer
Transmission cycles can be initiated by either of the following:
■ the expiration of a transmit countdown timing counter
■ a change to the status or value of one or more of the TLVs associated with
your local system
A series of successive changes over a short period of time can trigger the agent
to send a large number of LLDPDUs. To prevent this, there is a transmission
delay timer. This establishes a minimum length of time that must elapse
between successive LLDP transmissions. The default is two seconds, but you
can configure this to suit your network. For more information, see the set lldp
txdelay command on page 27.
Reception
When LLDP reception is enabled on a port, the LLDP agent receives
advertised information from and about remote neighbouring devices, and
stores this data in the remote systems MIB. For more information, see “LLDP
Remote Systems MIB” on page 6.
When LLDP reception is disabled on a port, the LLDP agent does not receive
any neighbour advertisements.