Unstable indicates that a port or interface repeatedly alternates between up and down states over a short period of time and is considered unstable. The LinkTrapThreshold and LinkTrapWindow parameters contained in the Interface/Port Flapping setting control analysis for the network adapter unstable condition.

An Unstable notification is only generated when the port or interface is not physically connected. When a port or interface is physically connected, network adapter Unstable is superseded by a NetworkConnection Unstable diagnosis.

For ports, this means that Port Unstable is superseded by:

  • TrunkCable Unstable if the port is connected through a trunk cable.

  • Cable Unstable if the port is connected through a cable.

    For interfaces, this means that Interface Unstable is superseded by:

  • NetworkConnection Unstable if the interface is connected through a physical network connection.

  • Cable Unstable if the interface is connected through a cable.


    By default, Interface Unstable analysis is not performed on ISDN B channel, ISDN D channel, backup, or dial-on-demand interfaces. “Diagnosis of Unstable Objects” explains how to enable Interface Unstable analysis for these types of interfaces. (in concepts guide)

    The events used to diagnose Unstable are nearly identical to the events used to diagnose Down:

  • DownOrFlapping

  • MightBeDown for any logically connected systems

    One additional condition is used to diagnose Unstable: the value of the IsFlapping attribute for one or both of the connected network adapters must be TRUE.