This field specifies RADIUS server failover behavior when the primary server goes down. When the primary server is down the controller moves on to the secondary or tertiary configured RADIUS Servers. If this field is set to primaryBackup(1), then the controller starts polling the primary RADIUS server to see if it is up. When the primary RADIUS server comes back, the controller automatically starts sending new access requests to the primary RADIUS server but pending requests continue with backup RADIUS server. The administrator can select between the two strategies, i.e. the existing roundRobin(0) or new primaryBackup(1). This only applies to Authentication, not to Accounting.