One possible solution to configure SRV1 as a DNS server that can resolve names from the contoso.com domain by using DC1 and all other names by using the root hint servers is to use conditional forwarding. Conditional forwarding allows a DNS server to forward queries for a specific domain name to another DNS server, while using the normal forwarding or root hint servers for other queries. Here are the steps to configure conditional forwarding on SRV1:

On SRV1, open DNS Manager from the Administrative Tools menu or by typing dnsmgmt.msc in the Run box.

In the left pane, right-click on Conditional Forwarders and select New Conditional Forwarder.

In the New Conditional Forwarder dialog box, enter contoso.com as the DNS Domain name.

In the IP addresses of the master servers box, enter the IP address of DC1, which is the DNS server for the contoso.com domain. You can also click on Resolve to verify the name resolution of DC1.

Optionally, you can check the box Store this conditional forwarder in Active Directory, and replicate it as follows if you want to store and replicate the conditional forwarder in AD DS. You can also select the replication scope from the drop-down list.

Click OK to create the conditional forwarder.

Now, SRV1 will forward any queries for the contoso.com domain to DC1, and use the root hint servers for any other queries. You can test the name resolution by using the nslookup command on SRV1 or another computer that uses SRV1 as its DNS server. For example, you can run the following commands:

nslookup www.contoso.com

nslookup www.microsoft.com

The first command should return the IP address of www.contoso.com from DC1, and the second command should return the IP address of www.microsoft.com from a root hint server.