This scopes what this particular configured server row is actually used for, restricting it to just user-login authentication or to all RADIUS-authenticated functions on the device. An admin dedicating a specific, perhaps lower-capacity server to just user logins, while pointing other authentication needs elsewhere, uses this setting to enforce that split. For example, setting this to 'userLogin' on a small branch-office RADIUS server reserves it for administrator CLI logins only, while a separate, higher-capacity server handles all other RADIUS-authenticated needs on the device.