Usage Scenario
To configure detection parameters for OSPF neighbor relationship flapping suppression on an interface, run the ospf suppress-flapping peer command. However, keeping the default configurations is recommended.
By default, OSPF neighbor relationship flapping suppression is enabled on all interfaces in the same OSPF process. To disable the function from one of the interfaces, run the
ospf suppress-flapping peer disable command.
When an interface enters the flapping suppression state, all neighbor relationships on the interface enter the state accordingly.
Flapping suppression works in either Hold-down or Hold-max-cost mode.
- Hold-down mode: In the case of frequent flooding and topology changes during neighbor relationship establishment, interfaces prevent neighbor relationship reestablishment during Hold-down suppression, which minimizes LSDB synchronization attempts and packet exchanges.
- Hold-max-cost mode: If the traffic forwarding path changes frequently, interfaces use 65535 as the cost of the flapping link during Hold-max-cost suppression, which prevents traffic from passing through the flapping link.
Flapping suppression can also work first in Hold-down mode and then in Hold-max-cost mode.
By default, the Hold-max-cost mode takes effect. To configure the Hold-down mode and set duration for this mode, run the ospf suppress-flapping peer hold-down interval command.
If the hold-max-cost mode is configured for OSPF flapping suppression, you can run the ospf suppress-flapping peer resume-interval resume-interval command to set the interval for exiting from OSPF neighbor relationship flapping suppression. The resume-interval parameter value is an integer ranging from 2 to 1000, in seconds. Its default value is 120 seconds.
Prerequisites
OSPF neighbor relationship flapping suppression must have been enabled globally before you configure detection parameters for it. By default, the function is enabled. If it is disabled, run the undo suppress-flapping peer disable command to enable it before you configure the detection parameters.
OSPF neighbor relationship flapping suppression must have been enabled globally before you enable the function on an interface using the
undo ospf suppress-flapping peer disable command. By default, the function is enabled globally. If it is disabled, run the
undo suppress-flapping peer disable command to enable it first.
OSPF neighbor relationship flapping suppression must have been enabled globally before you configure the Hold-down mode and set duration for this mode. By default, the function is enabled. If it is disabled, run the
undo suppress-flapping peer disable command to enable it before you configure the Hold-down mode and set duration for this mode.
OSPF neighbor relationship flapping suppression must have been enabled globally before you configure duration for the Hold-max-cost mode. By default, the function is enabled. If it is disabled, run the
undo suppress-flapping peer disable command to enable it before you configure duration for the Hold-max-cost mode.
Precautions
The Hold-max-cost mode takes effect only unidirectionally. If a remote device does not support OSPF neighbor relationship flapping suppression, bidirectional traffic between the local and remote devices may travel along different paths.
When the OSPF neighbor relationship flaps again, the hold-max-cost timer will be restarted. If the flapping persists, the corresponding link may fail to exit from the flapping suppression state.
If hold-down is configured, flapping suppression works first in hold-down mode and then in hold-max-cost mode by default. If only the hold-down mode is required, run the ospf suppress-flapping peer hold-max-cost disable command to disable the hold-max-cost mode.