This string is the ELAN name returned to a configuration request whose ATM address matches this entry's configured address/mask pair, providing address-based (rather than MAC- or route-descriptor-based) ELAN assignment. An admin cares because ATM-address-based mapping is typically used for entire ranges of clients sharing an address prefix, so a wrong or missing value here can misroute a whole block of devices into the default ELAN instead of their intended one. For example, an address/mask pair covering a department's ATM address range could be mapped here to 'engineering-elan' so all matching clients land there automatically.