Virtual Router Redundancy Protocol is the open standard alternative to HSRP. It works across vendors.
VRRP calls its primary router the Master (not Active). The Master owns the virtual IP and responds to ARP requests. Backup routers monitor the Master via advertisements sent every second by default.
A unique VRRP feature: the virtual IP can be the same as a physical interface IP. The router with that IP always becomes Master with priority . This simplifies configuration when you want a specific router to be primary.