Configuring OSPF Neighbor Relationship Flapping Suppression

OSPF neighbor relationship flapping suppression works by delaying OSPF neighbor relationship reestablishment or setting the link cost to the maximum value.

Usage Scenario

If an interface carrying OSPF services alternates between Up and Down, OSPF neighbor relationship flapping occurs on the interface. During the flapping, OSPF frequently sends Hello packets to reestablish the neighbor relationship, synchronizes LSDBs, and recalculates routes. In this process, a large number of packets are exchanged, adversely affecting neighbor relationship stability, OSPF services, and other OSPF-dependent services, such as LDP and BGP. OSPF neighbor relationship flapping suppression can address this problem by delaying OSPF neighbor relationship reestablishment or preventing service traffic from passing through flapping links.

The following steps are optional, choose them as required.

Pre-configuration Tasks

Before configuring OSPF neighbor relationship flapping suppression, complete the following tasks:

Configure an IP address for each interface to ensure that neighboring routers are reachable at the network layer.
Configure basic OSPF functions.

Procedure

Run system-view
The system view is displayed.

To disable OSPF neighbor relationship flapping suppression globally, run the suppress-flapping peer disable command.
Run interface interface-type interface-number
The interface view is displayed.

To disable OSPF neighbor relationship flapping suppression from one of the interfaces, run the ospf suppress-flapping peer disable command.
Run ospf suppress-flapping peer hold-down interval
The Hold-down mode is configured, and its duration is set.

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.
  
  To change the maximum cost for OSPF links, run the maximum-link-cost cost command.
Flapping suppression can also work first in Hold-down mode and then in Hold-max-cost mode.

To disable the Hold-max-cost mode, run the ospf suppress-flapping peer hold-max-cost disable command.
Run ospf suppress-flapping peer { detecting-interval detecting-interval | threshold threshold | resume-interval resume-interval } ^*
Detection parameters are configured for OSPF neighbor relationship flapping suppression.
- Specifies the interval for exiting from OSPF neighbor relationship flapping suppression.
  
  If the interval between two successive neighbor status changes from Full to a non-Full state is longer than resume-interval, the flapping_count is reset.
- If OSPF neighbor relationship flapping suppression works in hold-max-cost mode, resume-interval indicates the duration of this mode.
The value of resume-interval must be greater than that of detecting-interval.
Using the default detection parameters is recommended.
Run quit
The system view is displayed.
Run quit
The user view is displayed.
Run reset ospf process-id suppress-flapping peer [ interface-type interface-number ] [ notify-peer ]
Interfaces are forced to exit from OSPF neighbor relationship flapping suppression.
Interfaces exit from flapping suppression in the following scenarios:
- The suppression timer expires.
- The corresponding OSPF process is reset.
- An OSPF neighbor is reset using the reset ospf peer command.
- OSPF neighbor relationship flapping suppression is disabled globally using the suppress-flapping peer disable command in the OSPF view.
- The reset ospf suppress-flapping peer command is run.
Run commit
The configuration is committed.

Checking the Configurations

Run the display ospf [ process-id ] interface interface-type interface-number verbose command to check the status of OSPF neighbor relationship flapping suppression.