netmon.cf file :

In PowerHA, heartbeating is used to monitor an adapter’s state over a long period of time. When heartbeating is not working, a decision must be made about whether the local adapter has gone bad or there are other network problems. This decision is made based on whether any network traffic can be seen on the local adapter, using the inbound byte count of the interface. Where VIO is involved, this test becomes unreliable because there is no way to distinguish whether inbound traffic came in from the outside world through VIOS, or from a neighboring virtual I/O client.

A new netmon.cf function was added to support PowerHA in a virtual I/O environment, where PowerHA could not detect a local adapter-down event. This is because traffic being passed between the VIO clients looks like normal external traffic. The new format helps to decide, that adapter is up only, if it can ping a specified target.

The netmon.cf file must be placed in the /usr/es/sbin/cluster directory on all cluster nodes. Up to 32 targets can be provided for each interface. If any specific target is pingable, the adapter will be considered “up.” (The traditional format of the netmon.cf file is not valid in PowerHA v7, and later, and is ignored. Only the !REQD lines are used.)

example content of /usr/es/sbin/clister/netmon.cf:
!REQD en2 100.12.7.9
!REQD en2 100.12.7.10

Interface en2 is considered “up” only if it can ping either 100.12.7.9 or 100.12.7.10.