Management and Configuration Guide K/KA/KB.15.15

802.1X blocking
Ports blocked by 802.1X operation do not allow transmission or receipt of LLDP packets.
LLDP operation on the switch
Enabling LLDP operation (the default) causes the switch to:
• Use active, LLDP-enabled ports to transmit LLDP packets describing itself to neighbor devices.
• Add entries to its neighbors table based on data read from incoming LLDP advertisements.
Time-to-Live for transmitted advertisements
The Time-to-Live value (in seconds) for all LLDP advertisements transmitted from a switch is controlled
by the switch that generates the advertisement and determines how long an LLDP neighbor retains
the advertised data before discarding it. The Time-to-Live value is the result of multiplying the
refresh-interval by the holdtime-multiplier.
Delay interval between advertisements
The switch uses a delay-interval setting to delay transmitting successive advertisements resulting
from these LLDP MIB changes. If a switch is subject to frequent changes to its LLDP MIB, lengthening
this interval can reduce the frequency of successive advertisements. You can change the
delay-interval by using either an SNMP network management application or the CLI setmib
command.
Reinitialize delay interval
In the default configuration, a port receiving a disable command followed immediately by a
txonly, rxonly, or tx_rx command delays reinitializing for two seconds, during which LLDP
operation remains disabled. If an active port is subjected to frequent toggling between the LLDP
disabled and enabled states, LLDP advertisements are more frequently transmitted to the neighbor
device. Also, the neighbor table in the adjacent device changes more frequently as it deletes, then
replaces LLDP data for the affected port which, in turn, generates SNMP traps (if trap receivers
and SNMP notification are configured.) All of this can unnecessarily increase network traffic.
Extending the reinitialization-delay interval delays the ability of the port to reinitialize and generate
LLDP traffic following an LLDP disable/enable cycle.
SNMP notification support
You can enable SNMP trap notification of LLDP data changes detected on advertisements received
from neighbor devices and control the interval between successive notifications of data changes
on the same neighbor.
Changing the minimum interval
If LLDP trap notification is enabled on a port, a rapid succession of changes in LLDP information
received in advertisements from one or more neighbors can generate a high number of traps. To
reduce this effect, you can globally change the interval between successive notifications of neighbor
data change.
Basic LLDP per-port advertisement content
In the default LLDP configuration, outbound advertisements from each port on the switch include
both mandatory and optional data.
256 Configuring for Network Management Applications