Hot Standby Router Protocol (HSRP) is a redundancy routing protocol that establishes default fault tolerance and a framework for primary network gateway failover. HSRP is designed for multiaccess or broadcast local area networks (LAN) and supports non-disruptive Internet Protocol traffic inaccessibility.
HSRP is defined as RFC 2281.
Techopedia Explains Hot Standby Router Protocol
HSRP features include:
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.
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