Windows Server 2025 / DNS Basics: Zones, Records, and Name Resolution

The Domain Name System (DNS) finds IP addresses and service locations for names. Windows Server stores records in zones, and Active Directory also uses DNS to locate domain controllers and directory services.

A lookup asks a configured DNS server a specific question

A client sends a name and record type to a resolver. The server can answer from its own zones or use cache, forwarding, or recursion for other names. A name-to-address relationship is not necessarily permanent.

For example, fs1.lab.example.test can identify 172.24.50.20 so users need not memorize its address. Creating that record does not install file sharing, a website, or authentication, and does not grant access. Test name resolution and the actual service separately.

A zone defines an administered part of the namespace

This course separates the practice zone lab.example.test from the later AD domain ad.example.test. Both use example namespaces. Microsoft’s zone documentation describes storage and replication choices.

AD integration is not available on every standalone DNS server. Before DC1 is promoted, use a file-backed primary zone for practice and create the domain’s directory-integrated zone during domain setup.

Record types contain different kinds of data

A CNAME target must resolve. Web aliases can also need matching bindings and certificates; SMB aliases can have service-side requirements. DNS alone does not complete a service rename.

A missing reverse record can cause nslookup to label a DNS server Unknown even when the requested A lookup works. Reverse lookup and forward lookup are separate tests; not every application requires both.

Account for caching and TTL

Time to Live (TTL) controls how long a response can be cached. A changed record may remain old on another resolver or client until its cache changes. Compare the same name, record type, and server:

Resolve-DnsName -Name 'fs1.lab.example.test' -Type A -Server 172.24.50.10
nslookup fs1.lab.example.test 172.24.50.10

Run these on CLIENT1 after creating the zone and record. The expected A result includes 172.24.50.20. Before configuration, failure is expected. A nonexistent-name response and a timeout indicate different problems.

Use internal DNS for domain discovery

A domain computer uses DNS to locate controllers. Internet browsing alone does not establish healthy domain DNS: public resolvers do not know a private AD zone’s SRV records. Keep internal discovery on internal DNS and plan forwarding for external names.

Before manually editing AD service records, understand their role and registration process. Practice A, CNAME, and PTR changes in the separate practice zone so that ordinary DNS exercises do not damage domain discovery.