Your network consists of an Active Directory forest that contains one domain. All domain  
controllers run Windows Server 2008 R2 and are configured as DNS servers. You have an Active  Directory- integrated zone.    
You have two Active Directory sites. Each site contains five domain controllers.    
You add a new NS record to the zone.
You need to ensure that all domain controllers immediately receive the new NS record.    
What should you do（）

Your company has an Active Directory domain named ad.contoso.com. The domain has two  domain controllers named DC1 and DC2. Both domain controllers have the DNS Server server  role installed.    
You install a new DNS server named DNS1.contoso.com on the perimeter network. You  configure DC1 to forward all unresolved name requests to DNS1.contoso.com.  
You discover that the DNS forwarding option is unavailable on DC2. You need to configure DNS  forwarding on the DC2 server to point to the DNS1.contoso.com server. Which two actions should  you perform（）