Quick reminder about HSRP ~ Sysnet Notes

In this article we will discuss about brief about HSRP

Quick reminder about HSRP

Hot Standby Router Protocol (HSRP) is a Cisco proprietary protocol.
With HSRP, two or more devices support a virtual router with a fictitious MAC address and unique IP address
Hosts use this IP address as their default gateway and the MAC address for the Layer 2 header
The virtual router’s MAC address is 0000.0c07.ACxx , in which xx is the HSRP group. Multiple groups (virtual routers) are allowed.
The Active router forwards traffic. The Standby router is backup and monitors periodic hellos (multicast to 224.0.0.2,
UDP port 1985) to detect a failure of the active router.
The active router is chosen because it has the highest HSRP priority (default priority is 100). In case of a tie, the router
with the highest configured IP address wins the election
A new router with a higher priority does not cause an election unless it is configured to preempt.

HSRP States

Initial: HSRP is not running.
Learn: The router does not know the virtual IP address and is waiting to hear from the active router.
Listen: The router knows the IP and MAC of the virtual router, but it is not the active or standby router.
Speak: Router sends periodic HSRP hellos and participates in the election of the active router.
Standby: Router monitors hellos from active router and assumes responsibility if active router fails.
Active: Router forwards packets on behalf of the virtual router.

Sysnet Notes