Understand HSRP States and HSRP State Transitions

HSRP States

 In HSRP process, Router will go through the below states and finally Router will stay in Active or Standby or Listen state. An HSRP router can be in one of six different states.

• Initial

• Learn

• Listen

• Speak

 • Standby

• Active 

Initial State

This is first and starting state, The initial state indicates that HSRP does not run. This state is entered via a configuration change or when an interface first comes up.

Learn State

The router is neither in the active or standby state, nor does it have enough information to attempt to claim the active or standby role.

Listen State

The router knows the virtual IP address of HSRP group, but the router is neither the active router nor the standby router. It listens for hello messages from those routers.

Speak State

The router sends periodic hello messages and actively participates in the election of the active or standby router. A router cannot enter speak state unless the router has the virtual IP address of HSRP group.

Standby State

The router is a candidate to become the next active router and sends periodic hello messages. With the exclusion of transient conditions, there is, at most, one router in the group in standby state.

Active State

The router currently forwards packets that are sent to the group virtual MAC address (0000.0c07.acXX). The router sends periodic hello messages. With the exclusion of transient conditions, there must be, at the most, one router in the active state in the group.

HSRP Transition Sates

All the Routers in the HSRP group will not transition through all states. For example, if there were three Routers in the HSRP group, the Router that is either standby or active Router will remain in the listen state only.

In below example, Router A with Highest Priority 120, Router B with priority 100 and Router C with Priority 90 in HSRP group 1. Find below HSRP transition states of all three Routers.

Router A

Router A having highest priority 120 in the HSRP group 1, it will go through below states.

Initial State –>Learn State –> Listen State  –> Speak State (Router A does not hear any higher priority than itself, so promotes itself to standby) –>Standby State (Router A does not hear an active router, so promotes itself to active)–>Active State.

Router B

Router B having 2nd highest priority 100 in the HSRP group 1, It will go through below states.

Initial State–>Learn State –>Listen State –>Speak State (Router B hears that router A has a higher priority, so router B returns to the listen state) –>Listen State–>Speak State (Router B does not hear any second higher priority than itself, so promotes itself to standby)–> Standby State.

Router C:

Router C having 3rd highest priority 90 in HSRP group 1, It will go through the below states.

Initial State–>Learn State –>Listen State –>Speak State (Router C hears that Router A has a higher priority and Router B has a second higher priority, so Router C returns to the listen State  ) –>Listen State

In HSRP, one Router will become a Active Router, one Router become a Standby Router and remaining all Routers are in a Listen state only.

Filed Under: HSRP/VRRP/GLBP

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