Route Flap Damping
Route Flap Damping Overview
Weighted route dampening treats routes that are being announced and withdrawn (flapping) at a rapid rate as unreachable. If a route flaps at a low rate, it should not be suppressed at all, or suppressed for only a brief period of time. With weighted route dampening, the suppression of a route or routes occurs in a manner that adapts to the frequency and duration that a particular route appears to be flapping. The more a route flaps during a period of time, the longer it will be suppressed. The adaptive characteristics of weighted route dampening are controlled by a few tags.
Note: Route flap damping currently only applies to BGP.
dampen-flap
Name
dampen-flap - enters the user into Dampen Flap Configuration mode
Syntax
dampen-flap name
no dampen-flap name
Mode
Global Configuration
Parameters
name - a string of characters uniquely identifying a dampen-flap configuration
Description
The dampen-flap command enters the user into Dampen Flap Configuration mode, where route-flap-damping parameters can be specified. The negative form of this command, no dampen-flap, removes the configured damping.
Default
This command is not explicitly configured by default.
Command History
NGC 2.2 - This command was introduced.
Examples
The following example configures route flap damping with an ID of rfd1.
(config)# dampen-flap rfd1
(config-dampen-flap)#
keep-history
Name
keep-history - specifies the time in seconds for which any history of a route's instability is maintained
Syntax
keep-history time-seconds
no keep-history time-seconds?
Mode
Dampen Flap Configuration
Parameters
time-seconds - specifies a time in seconds from 1 to 604800, inclusive
Description
The keep-history command specifies time in seconds for which any history of a route’s instability is maintained. The negative form of this command, no keep-history, removes the configured value and returns this to its default value of 1800 seconds. Note: Specifying a value for time-seconds in the no form has no effect on the configuration. Thus, it is displayed above as optional.
Default
If keep-history is not specified, it is the same as if the user had specified the following:
(config-dampen-flap)# keep-history 1800
Command History
NGC 2.2 - This command was introduced.
Examples
The following example configures the keep-history value to be 2000 seconds.
(config)# dampen-flap rfd1
(config-dampen-flap)# keep-history 2000
max-flap
Name
max-flap - specifies the maximum value of a route’s instability history
Syntax
max-flap float
no max-flap float?
Mode
Dampen Flap Configuration
Parameters
float - an integer or floating point number between 2.1 and 604800, inclusive
Description
Use the max-flap command to specify the maximum value of a route’s instability history. The instability metric is incremented by 1 each time a route becomes unreachable. The max-flap value, which must be greater than the suppress-above value, determines the longest time that a route can be suppressed.
The negative form of this command, no max-flap, removes the configured value and returns this to its default value of 16.0. Note: Specifying a value for float in the no form has no effect on the configuration. Thus, it is displayed above as optional.
Default
If max-flap is not specified, it is the same as if the user had specified the following:
(config-dampen-flap)# max-flap 16.0
Command History
NGC 2.2 - This command was introduced.
Examples
The following example configures the maximum value of the route’s instability history to be 18.
(config)# dampen-flap rfd1
(config-dampen-flap)# max-flap 18
See Also
"suppress-above"
reach-decay
Name
reach-decay - specifies the time in seconds after which a reachable route’s instability history decays to half of its current value
Syntax
reach-decay time-seconds
no reach-decay time-seconds?
Mode
Dampen Flap Configuration
Parameters
time-seconds - specifies a time in seconds from 1 to 604800, inclusive
Description
Use the reach-decay command to specify a time in seconds, after which a reachable route’s instability history decays to half of its current value. The negative form of this command, no reach-decay, removes the configured value and returns this to its default value of 300 seconds. Note: Specifying a value for time-seconds in the no form has no effect on the configuration. Thus, it is displayed above as optional.
Default
If reach-decay is not specified, it is the same as if the user had specified the following:
(config-dampen-flap)# reach-decay 300
Command History
NGC 2.2 - This command was introduced.
Examples
The following example configures the reach-decay value to be 600 seconds.
(config)# dampen-flap rfd1
(config-dampen-flap)# reach-decay 600
reach-tick
Name
reach-tick - specifies the granularity of instability history in seconds
Syntax
reach-tick time-seconds
no reach-tick time-seconds?
Mode
Dampen Flap Configuration
Parameters
time-seconds - an integer between 1 and 604800, inclusive, used to specify the time in seconds
Description
The reach-tick command specifies the granularity of instability history in seconds. The negative form of this command, no reach-tick, removes the configured value and returns this to its default value of 1 second. Note: Specifying a value for time-seconds in the no form has no effect on the configuration. Thus, it is displayed above as optional.
Default
If reach-tick is not specified, it is the same as if the user had specified the following:
(config-dampen-flap)# reach-tick 1
Command History
NGC 2.2 - This command was introduced.
Examples
The following example configures the reach-tick value to be 5 seconds
(config)# dampen-flap rfd1
(config-dampen-flap)# reach-tick 5
reuse-below
Name
reuse-below - specifies the value of a route’s instability, below which a suppressed route is reused
Syntax
reuse-below float
no reuse-below float?
Mode
Dampen Flap Configuration
Parameters
float - a floating point number whose value is less than or equal to the suppress-above value, and in the range of 1.0 to 604800, inclusive
Description
The reuse-below command specifies the value of a route’s instability metric, below which a suppressed route is reused. The value for this command must be less or equal to the suppress-above value.
The negative form of this command, no reuse-below, removes the configured value and returns this to its default value of 1.0. Note: Specifying a value for float in the no form has no effect on the configuration. Thus, it is displayed above as optional.
Default
If reuse-below is not specified, it is the same as if the user had specified the following:
(config-dampen-flap)# reuse-below 1.0
Command History
NGC 2.2 - This command was introduced.
Examples
The following example configures the reuse-below value to be 6
(config)# dampen-flap rfd1
(config-dampen-flap)# reuse-below 6
See Also
"suppress-above"
suppress-above
Name
suppress-above - specifies the value of a route’s instability, above which the route is suppressed
Syntax
suppress-above float
no suppress-above float?
Mode
Dampen Flap Configuration
Parameters
float - a floating point number whose value is greater than or equal to the reuse-above value, and in the range of 2.0 to 604800, inclusive
Description
The suppress-above command specifies the value of a route’s instability metric, above which the route is suppressed. The negative form of this command, no suppress-above, removes the configured value and returns this to its default value of 2.0. Note: Specifying a value for float in the no form has no effect on the configuration. Thus, it is displayed above as optional.
Default
If suppress-above is not specified, it is the same as if the user had specified the following:
(config-dampen-flap)# suppress-above 2.0
Command History
NGC 2.2 - This command was introduced.
Examples
The following example configures the suppress-above value to be 8.
(config)# dampen-flap rfd1
(config-dampen-flap)# suppress-above 8
See Also
"reuse-below"
unreach-decay
Name
unreach-decay - specifies the time in seconds after which an unreachable route’s instability history decays to half its current value
Syntax
unreach-decay time-seconds
no unreach-decay time-seconds?
Mode
Dampen Flap Configuration
Parameters
time-seconds - specifies a time in seconds from 1 to 604800, inclusive
Description
Use the unreach-decay command to specify a time in seconds, after which a unreachable route’s instability history decays to half of its current value. The negative form of this command, no unreach-decay, removes the configured value and returns this to its default value of 900 seconds. Note: Specifying a value for time-seconds in the no form has no effect on the configuration. Thus, it is displayed above as optional.
Default
If unreach-decay is not specified, it is the same as if the user had specified the following:
(config-dampen-flap)# unreach-decay 900
Command History
NGC 2.2 - This command was introduced.
Examples
The following example configures the unreach-decay value to be 600 seconds.
(config)# dampen-flap rfd1
(config-dampen-flap)# unreach-decay 600
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