Enabling override changes the order of primary unit selection. As shown in Figure 189 if override is enabled, primary unit selection considers device priority before age and serial number. This means that if you set the device priority higher on one cluster unit, with override enabled this cluster unit becomes the primary unit even if its age and serial number are lower than other cluster units.

Similar to when override is disabled, when override is enabled primary unit selection checks for connected monitored interfaces first. So if interface monitoring is enabled, the cluster unit with the most disconnected monitored interfaces cannot become the primary unit, even of the unit has the highest device priority.

If all monitored interfaces are connected (or interface monitoring is not enabled) and the device priority of all cluster units is the same then age and serial number affect primary unit selection.