Your company has a main office and two branch offices. Domain controllers in the main office host an Active Directory-integrated zone. The DNS servers in the branch offices host a secondary zone for the domain and use the main office DNS servers as the DNS Master servers for the zone.Each branch office has an application server. Users access the application server by using its fully qualified domain name.You need to ensure that users in the branch offices can access their local application server even if the WAN links are down for three days.What should you do？（）