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Controlling Route Flapping Through Route Dampening Configuring BGP
page 4-38 OmniSwitch 6800/6850/9000 Advanced Routing Configuration Guide December 2007
Setting the Reuse Value
The dampening reuse value is used to determine if a route should be re-advertised. If the number of flaps
for a route falls below this number, then the route is re-advertised. For example, if the reuse value is set at
150, and a route with 250 flaps exceeds the reach halflife it would be re-advertised as its flap number
would now be 125.
To change one variable to a number different than its default value, you must enter all of the variables with
the ip bgp dampening command in the correct order.
For example, to set the reuse value to 500, enter the reuse value and other variables with the following
command, as shown:
-> ip bgp dampening half-life 300 reuse 500 suppress 300 max-suppress-time 1800
In this example, the other variables have been set to their default values. The reuse value is now set to 500.
The default value is 200.
Setting the Suppress Value
The dampening suppress value sets the number of times a route can flap before it is suppressed. A
suppressed route is not advertised. For example, if the cutoff value is set at 200, and a route flaps 201
times, it will be suppressed.
To change one variable to a number different than its default value, you must enter all of the variables with
the ip bgp dampening command in the correct order.
For example, to set the suppress value to 500, enter the suppress value and other variables with the follow-
ing command, as shown:
-> ip bgp dampening half-life 300 reuse 200 suppress 500 max-suppress-time 1800
In this example, the other variables have been set to their default values. The suppress value is now set to
500. The default value is 300.
Setting the Maximum Suppress Holdtime
The maximum suppress holdtime is the number of seconds a route stays suppressed once it has crossed the
dampening cutoff flapping number. For example, if the maximum holdtime is set to 500, once a route is
suppressed the local BGP speaker would wait 500 seconds before advertising the route again.
To change one variable to a number different than its default value, you must enter all of the variables with
the ip bgp dampening command in the correct order.
For example, to set the maximum suppress holdtime value to 500, enter the maximum suppress holdtime
value and other variables with the following command, as shown:
-> ip bgp dampening half-life 300 reuse 200 suppress 300 max-suppress-time 500
In this example, the other variables have been set to their default values. The maximum suppress holdtime
is now set to 500 seconds. The default value is 1800 seconds.