Maintaining an alternate data path is an essential best practice for effective network monitoring. In the event of a failure of your primary data path, the alternate path allows your master to maintain continuous visibility of equipment at your remote sites.
In this application, the LAN is the primary data path between the master and the remotes. The secondary alternate path is a dial-up connection to the public switch telephone network (PSTN). If the LAN fails, both the master and the remotes will automatically maintain communication via the alternate path.