Ideally, HA Checks should be set for every interface that will be in use for production traffic. This includes, but is not limited to the interfaces that are used to pass traffic for virtual services, server pools and default gateway traffic.
HA Checks can also be included on management interfaces, but be aware that LoadMaster will become standby in the event that this network goes down.
For optimal HA operation, at least two interfaces should be configured to use HA Checks. If you only use one interface for all traffic, a crossover cable may be connected between both units on eth1. The interface will automatically configure and no IP addressing should be applied to this link.
The only time you must not have HA Checks enabled is for IP addressed interfaces directly connected to the partner device. This will cause the pair to both fail should the link go down for any reason. This inhibits normal HA function.