There is one direct cable connected between Primary node and Secondary node, The cable connection is not via switch. Both interfaces are HA MON enabled.

Both NetScaler HA nodes status turn to NOT_UP after Primary HA-MON enabled interface is down.



 

Direct cable connection is not recommended for NetScaler HA deployment. Highly suggest all cable connection is through switch.
In case when direct cable is applied between HA nodes, it is recommended to disable HA MON for those interfaces of both NetScaler nodes.

To disable interface HA MON:

1. Navigate to System > Network > Interfaces.
2. Select the interface for which the monitor must be disabled.
3. Click Edit.
4. In HA Monitoring, select the OFF option.
5. Click OK.

 

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Problem Cause

After Primary interface is down, HA failover is triggered and HA node state switch happened between two nodes.
The new Secondary node, due to HA MON interface status down, it'll reset all interfaces and interfaces status flapped accordingly. Since the direct cable between 2 nodes, the new Primary node will also found it's HA MON interface status DOWN. 
Both nodes will report status NOT_UP in this situation.