Phones - Why does my Digium phone say Failover Mode and what does it mean?

Starting in Switchvox SMB 5.5.4 v48406, thePhone Networkssetting includes anAlternate Host Addresssetting. In the event that a Digium phone can no longer reach the Switchvox at theHost Address, the phone will register to theAlternate Host Address. If this happens, the phone will be inFailover Mode, and many of its phone applications will not be available for use. The phone should be able to make and receive calls over theAlternate Host Addressuntil theHost Addressbecomes available.