Configuring Dampening On An Ethernet Interface - H3C S6850 Series Configuration Manual

You can configure different suppression intervals for link-up and link-down events.
If you execute the link-delay command multiple times on an interface, the following rules apply:
•
You can configure the suppression intervals for link-up and link-down events separately.
•
If you configure the suppression interval multiple times for link-up or link-down events, the most
recent configuration takes effect.
The link-delay , dampening , and port link-flap protect enable commands are
mutually exclusive on an Ethernet interface.
Procedure
1. Enter system view.
system-view
2. Enter Ethernet interface view.
interface interface-type interface-number
3. Configure physical state change suppression.
link-delay { down | up } [ msec ] delay-time
By default, each time the physical link of a port goes up or comes down, the interface
immediately reports the change to the CPU.

Configuring dampening on an Ethernet interface

About dampening
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 until the ceiling is reached. It does not increase for up
events. When the interface stops flapping, the penalty decreases by half each time the half-life
timer expires until the penalty drops to the reuse threshold.
•
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 penalty starts to decrease until it drops below the reuse
threshold.
When configuring the dampening command, follow these rules to set the values mentioned above:
•
The ceiling is equal to 2
•
The configured suppress limit is lower than or equal to the ceiling.
(Max-suppress-time/Decay)
× reuse-limit. It is not user configurable.
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