Hot Standby Router Protocol (HSRP)

• Consistent IP routing protocol sets
• Works in a bridging environment
• Automatically self-updates when media access control (MAC) addresses are modified
• High-priority HSRPs are virtual (or active) routers with predefined gateway IP addresses
• HSRP groups or standby groups are HSRP router sets coordinated as illusory single active routers
• HSRP group routers have universal IP and MAC addresses.
• The virtual IP address for an HSRP group is the primary IP address LAN subnet and differs from other allocated interface addresses.
  

HSRP and active routers transmit messages on a periodic basis upon completion of protocol election. When an HSRP router fails or becomes an active router, the next standby router is selected to handle packet-forwarding duties. The active router then accepts and forwards traffic to the group’s virtual MAC address. When the active router leaves the LAN state, packet forwarding ends.