Detecting Physical Interface Repairs

Repair detection time is twice the failure detection time. The default time for failure detection is 10 seconds. Accordingly, the default time for repair detection is 20 seconds. After a failed interface has been marked with the RUNNING flag again and the failure detection method has detected the interface as repaired, the in.mpathd daemon clears the interface's FAILED flag. The repaired interface is redeployed depending on the number of active interfaces that the administrator originally set.

When an underlying interface fails and probe-based failure detection is used, the in.mpathd daemon continues probing, either by means of the designated prober when no test addresses are configured or by using the interface's test address. During an interface repair, the recovery process proceeds depending on the original configuration of the failed interface as follows:

• If the failed interface was originally an active interface, the repaired interface reverts to its original active status. The standby interface that functioned as a replacement during the failure is switched back to standby status if enough interfaces are active for the IPMP group as defined by the system administrator.

  ---

  Note - An exception is when the repaired active interface is also configured with the FAILBACK=no mode. For more information, see FAILBACK=no Mode

  ---

• If the failed interface was originally a standby interface, the repaired interface reverts to its original standby status, provided that the IPMP group reflects the original number of active interfaces. Otherwise, the standby interface becomes an active interface.

To see a graphical presentation of how IPMP operates during interface failure and repair, see How IPMP Works.

FAILBACK=no Mode

By default, active interfaces that have failed and then been repaired automatically return to become active interfaces in the IPMP group. This behavior is controlled by the value of the FAILBACK parameter in the in.mpathd daemon's configuration file. However, even the insignificant disruption that occurs as data addresses are remapped to repaired interfaces might not be acceptable to some administrators. These administrators might prefer to enable an activated standby interface to continue as an active interface. IPMP allows administrators to override the default behavior to prevent an interface from automatically becoming active upon repair. These interfaces must be configured in the FAILBACK=no mode. For related procedures, see How to Configure the Behavior of the IPMP Daemon.

When an active interface in FAILBACK=no mode fails and is subsequently repaired, the in.mpathd daemon restores the IPMP configuration as follows:

• The daemon retains the interface's INACTIVE status, provided that the IPMP group reflects the original configuration of active interfaces.

• If the IPMP configuration at the moment of repair does not reflect the group's original configuration of active interfaces, then the repaired interface is redeployed as an active interface, notwithstanding the FAILBACK=no status.