When do we select "Use this connection's DNS suffix in DNS registration"?

network layout:

DNS1:

Active Directory Integrated Zone: Microsoft.com

DNS2:

Active Directory Integrated Zone. Production.Microsoft.com

All DNS servers running on domain controllers will have both Microsoft.com zone and Production.Microsoft.com zone.

If PC1 and PC2 want to access FileServer2.Production.Microsoft.com, you should select "Use this connection's DNS suffix in DNS registration" as follows:

Microsoft.com zone will have FileServer2.Microsoft.com record.

Because the FileServer2 has the primary suffix Production.Microsoft.Com, DNS server 2 will have the FileServer2.Production.Microsoft.com record registered.

PC1 can resolve the FileServer2 hostname by FileServer2.Microsoft.com.

Without "Use this connection's DNS suffix in DNS registration", there is no FileServer2.Microsoft.com record registered. And PC1 cannot use the shortname FileServer2( the FQDN will be FileServer2.Microsoft.com). However, FQDN FileServer2.Production.Microsoft.com always works.

The computers in child domain production.microsoft.com can access the parent domain server FileServer1 without any problem.

Because "Append parent suffixes of the primary DNS suffix" is by default checked, when FileServer1.Production.Microsoft.com cannot be resolved, it will resolve FileServer1.Microsoft.com.

If you don't select "Use this connection's suffix in DNS registration" for FileServer1, PC1 and PC2 should have the following configuration.

PC1 will try FileServer1.Microsoft.com and then FileServer1.Production.Microsoft.com.