A router in an HSRP standby group can be in one of the following states:
initial, listen, speak, standby, or active.

When a
router exists in one of these states, the router performs the necessary actions
required for that state. Not all HSRP routers will transition through all
states. For example, a router that is not the standby or active router will not
enter the standby or active states.
HSRP Initial State
All
routers begin in the initial state.
This is
the starting state and indicates that HSRP is not running. This state is
entered via a configuration change or when an interface is initiated.
HSRP Listen State
In the listen state, the router knows the IP
address of the virtual router, but is neither the active router nor the standby
router. The router listens for hello messages from those routers for a duration
called the hold time which can be configured. The purpose of this
listening interval is to determine if there are active or standby routers for
the group. Then this router will join the HSRP group, based on its
configuration.

HSRP
Speak State
In the speak state, the router sends periodic hello
messages and is actively participating in the election of the active router or
standby router or both. A router cannot enter the speak state unless the router
has the IP address of the virtual router. The router will remain in the speak
state unless it becomes an active or standby router.

Standby State
In the standby state, because the router is a
candidate to become the next active router, it sends periodic hello messages.
It will also listen for hello messages from the active router. There will be
only one standby router in the HSRP group.

Active
State
In the active state, the router is currently forwarding packets
that are sent to the virtual MAC address of the group. It also replies to ARP
requests made of the virtual routers IP address. The active router sends
periodic hello messages. There must be one active router in each HSRP group.
