Availability and reachability were removed in LMS 2.5+. There is an add-on to LMS scheduled to ship this summer that will add MRTG-like capabilities to LMS 3.0. This will allow you to do some of the availability tasks that RME 3.x provided.
For now, DFM does provide fault information related to device reachability (though not in the same format that RME did in the past). You can use the Alerts and Activities Display under DFM to see if a device becomes unreachable.
