8
Step Command
Remarks
3.
Configure physical
state change
suppression.
link-delay
[
msec
]
delay-time
[
mode
{
up
|
updown
}]
By default, physical state change suppression is
disabled on an Ethernet interface.
You can configure different suppression intervals
for link-up and link-down events.
If you configure this command multiple times for
link-up or link-down events on an Ethernet
interface, the most recent configuration takes
effect.
Configuring dampening on an Ethernet interface
The interface dampening feature uses an exponential decay mechanism to prevent excessive interface
flapping events from adversely affecting routing protocols and routing tables in the network. Suppressing
interface state change events protects the system resources.
If an interface is not dampened, its state changes are reported. For each state change, the system also
generates an SNMP trap and log message.
After a flapping interface is dampened, it does not report its state changes to the CPU. For state change
events, the interface only generates SNMP trap and log messages.
Parameters
•
Penalty
—The interface has an initial penalty of 0. When the interface flaps, the penalty increases
by 1000 for each down event. It does not increase for up events.
•
Ceiling
—The penalty stops increasing when it reaches the ceiling.
•
Suppress-limit
—The accumulated penalty that triggers the device to dampen the interface. In
dampened state, the interface does not report its state changes to the CPU. For state change events,
the interface only generates SNMP traps and log messages
•
Reuse-limit
—When the accumulated penalty decreases to this reuse threshold, the interface is not
dampened. Interface state changes are reported to the upper layers. For each state change, the
system also generates an SNMP trap and log message.
•
Decay
—The amount of time (in seconds) after which a penalty is decreased.
•
Max-suppress-time
—The maximum amount of time the interface can be dampened. If the penalty
is still higher than the reuse threshold when this timer expires, the penalty stops increasing for down
events.
The ceiling is equal to 2
(Max-suppress-time/Decay)
× reuse-limit. It is not user configurable.
shows the change rule of the penalty value. The lines t
0
and t
2
indicate the start time and end
time of the suppression, respectively. The period from t
0
to t
2
indicates the suppression period, t
0
to t
1
indicates the max-suppress-time, and t
1
to t
2
indicates the complete decay period.
