Refer to the exhibit. HSRP has been configured and Link A is the primary route to router R4. When Link A fails, router R2 (Link B) becomes the active router. Which router will assume the active role when Link A becomes operational again?”

A.
The primary router R1 will reassume the active role when it comes back online.

B.
The standby router R2 will remain active and will forward the active role to router R1 only in the event of its own failure.

C.
The standby router R2 will remain active and will forward the active role to router R1 only in the event of Link B failure.

D.
The third member of the HSRP group, router R3, will take over the active role only in event of router R2 failure.

Explanation:

HSRP election is based on a priority value (0 to 255) that is configured on each router in the group. By default, the priority is 100. The router with the highest priority value (255 is highest) becomes the active router for the group. If all router priorities are equal or set to the default value, the router with the highest IP address on the HSRP interface becomes the active router. To set the priority, use the following interface configuration command:
Switch(config-if)# standby group priority priority

When HSRP is configured on an interface, the router progresses through a series of states before becoming active. This forces a router to listen for others in a group and see where it fits into the pecking order. The HSRP state sequence is Disabled, Init, Listen, Speak, Standby, and, finally, Active.
Only the standby (second highest priority) router monitors the hello messages from the active router. By default, hellos are sent every 3 seconds. If hellos are missed for the duration of the holdtime timer (default 10 seconds, or 3 times the hello timer), the active router is presumed down. The standby router is then clear to assume the active role. If other routers are sitting in the Listen state, the next-highest priority router is allowed to become the new standby router.