We offer two different types of fail-over in 9.x code...
Round-Robin: At start up, first configured server is selected as active server. When the current active server goes down, the next server is selected as the active server. There will be no polling for the original active server. Even when the original active server comes back. It will not be selected as active server. Primary-Backup: At start up, the first configured server is selected as primary server. When primary server goes down, the next available server is selected as the VNS’s active RADIUS server to send access-request packets. The controller sends polling packets to the primary server. When primary server comes back, the controller will use primary server to send new access-request packets and controller stops sending polling packet.
Doug Hyde
Director, Technical Support / Extreme Networks