A basic pre-requisite for all methods device configuration is for an IP connection to exist between the configuration computer and the device. No matter whether LANconfig, WEBconfig or Telnet is used; no configuration commands can be sent to the device without an IP connection. In the event of erroneous configuration of the TCP/IP settings or VLAN parameters, this IP connection may be impossible to establish. The only option in this case is to access the device via the serial configuration interface, which however is not available on all devices, or to reset the device to its factory settings. However, both options require physical access to the device—this may not always be the case for the concealed installation of access points and can represent considerable overhead for larger-scale installations.
The LANCOM Layer 2 Management Protocol (LL2M) is used to also enable configuration access to a device even without an IP connection. All this protocol requires is a connection on layer 2 (i.e. via Ethernet directly or via layer-2 switches) to establish a configuration session. LL2M connections are supported on LAN or WLAN connections, but not via WAN. Connections via LL2M are password protected and are resistant to replay attacks.
LL2M establishes a client-server structure for this purpose: The LL2M client sends requests or commands to the LL2M server, which then responds to the requests or runs the commands. The LL2M client is integrated into LCOS and is run from the command line. The LL2M server is also integrated into LCOS and is usually only enabled for a brief period after device power-on. In this time frame, an administrator can use the LL2M client to perform changes to the configuration of the device running the LL2M server.
