Windows Server 2025 / How to Configure DHCP Reservations and Options
A DHCP reservation associates a client identifier with an address; options supply settings such as DNS and gateways. The client must still use DHCP, and option changes must be verified on the client after lease renewal.
Distinguish reservations from manual static settings
| Method | Where it is configured |
|---|---|
| Manual static IP | Configured on the device; managed separately from DHCP |
| DHCP reservation | Client identifier and address mapped on the DHCP server; client remains automatic |
Leave essential servers such as DC1 on the static plan during this exercise. Practice reservations with CLIENT1, which already has a lease from .100–.150. A MAC-based reservation is not device authentication or an access-control boundary. Review scope and option behavior.
Convert a verified lease
- On DC1, open DHCP Manager → IPv4 → Lab Clients → Address Leases.
- Compare the lease address and client identifier with ipconfig /all at CLIENT1; do not rely only on its displayed name.
- Use the lease context menu to add a reservation.
- Inspect the reservation node and record its purpose, address, and identifier.
Converting an actual lease reduces identifier mistakes. For a manual reservation, choose a nonconflicting address in the scope and use the real client ID. Recreating a virtual NIC or changing its MAC can stop the reservation matching.
Get-DhcpServerv4Lease -ScopeId 172.24.50.0 Get-DhcpServerv4Reservation -ScopeId 172.24.50.0
Query on the server, then renew at CLIENT1’s console and verify that it receives the reservation. Use console access because address changes can end a remote session.
Check where options are configured
Options can exist at server, scope, reservation, and policy levels. Identify which setting applies rather than treating one scope’s example as a server-wide instruction.
| IPv4 option | Lab interpretation |
|---|---|
| 003 Router | Only a real gateway where routing is configured |
| 006 DNS Servers | Working internal DNS servers |
| 015 DNS Domain Name | Connection-specific suffix; does not perform domain joining |
Use scope options here. The practice suffix is lab.example.test; after AD exists it becomes ad.example.test. DNS remains the working DC1 at .10. Do not fill fields with nonexistent servers.
Change one option and compare the client result
Check the existing suffix, then temporarily change only option 015 for the isolated lab:
Get-DhcpServerv4OptionValue -ScopeId 172.24.50.0 Set-DhcpServerv4OptionValue -ScopeId 172.24.50.0 -DnsDomain 'ad.example.test'
Renew CLIENT1 and inspect its connection-specific suffix in ipconfig /all. If it remains different, check manual settings, reservation options, policies, and which DHCP server replied. Compare reserved addressing separately from DNS options; a suffix does not guarantee the domain already resolves.
To return to the practice zone, run the following and renew again. Keep the domain suffix instead if AD deployment is already complete:
Set-DhcpServerv4OptionValue -ScopeId 172.24.50.0 -DnsDomain 'lab.example.test'
Verify removal and diagnose mismatches
Before deleting a reservation, identify its address and client ID and remove only that entry. Removal does not rewrite a manually configured client or instantly release every lease. A later ordinary lease can reuse the same address, so a different IP is not a required proof of removal.
If matching fails, check automatic client configuration, scope state and capacity, authorization, the actual identifier, and competing DHCP responders. The DHCP configuration guide supports server checks; the final evidence is what the client actually receives.
