Final answer:
The best DNS routing policy for automatically rerouting traffic in case of a primary production site failure is Failover routing. It allows for seamless transition to a disaster recovery site without manual intervention.
Step-by-step explanation:
To ensure DNS availability and failover to a secondary site, the best DNS routing policy is Failover routing. Failover routing allows for the configuration of DNS to automatically reroute traffic to a disaster recovery (DR) site if the primary production site goes down.
This policy is suitable for scenarios where you have a primary site and a secondary site, and want to switch over to the secondary site in case of a failure at the primary.
Weighted routing would distribute the traffic according to different weights which is not suitable for a primary-secondary setup. Geolocation routing sends traffic based on the geographical location of the user which doesn’t fulfill the requirement of failover. Simple routing only allows for one address to be associated with a DNS record and does not support automatic failovers.