Real server active, standby, and disabled modes
By default the real server mode setting is active indicating that the real server is available to receive connections. If the real server is removed from the network (for example, for routine maintenance or because of a hardware or software failure) you can change the mode to standby or disabled. In disabled mode the FortiGate unit no longer sends sessions to the real server.
If a real server is in standby mode the FortiGate also does not send sessions to it unless other real servers added to the same virtual server become unavailable. For example:
• A virtual server that includes two real servers one in active mode and one in standby mode. If the real server in active mode fails, the real server in standby mode is changed to active mode and all sessions are sent to this real server.
• A virtual server includes three real servers, two in active mode and one in standby mode, if one of the real servers in active mode fails, the real server in standby mode is changed to active mode and sessions are load balanced between it and still operating real server. If both real servers in active mode fail, all sessions are sent to the real server in standby mode.