The large and growing range of functions in the firmware means that some models are unable to store two complete versions of the firmware at once. These devices benefit from the asymmetric FirmSafe feature.
With asymmetric FirmSafe, the device always contains a "complete version" along with a bare-bones version known as "minimal firmware". The minimal version normally remains unused, but it provides local access to the device after a failed upload of the complete firmware version (e.g. as a result of a power cut during the upload process) in order to load an executable version of the firmware onto the device (via LAN, WLAN, or the config interface).
The minimum firmware cannot be configured! Changes to the configuration via LANconfig, WEBconfig or Telnet are not stored to the device. Advanced functions, in particular the remote management via WAN or ISDN, are not available as long as the minimal firmware is active. However, the LL2M server is also active in a minimal firmware version and offers access to the device provided it is reachable from an LL2M client over layer 2 (Ethernet).
