Add a new Active Directory site: procedure...

Objective

Create an Active Directory site that represents a real network location, associate its IP subnets, connect it to the replication topology, and verify that clients and domain controllers select the expected site.

Protect emergency access and avoid broad permission changes that can lock out administrators or expose privileged credentials.
Replication, Kerberos and policy changes can have delayed effects; validate on a pilot scope before broad enforcement.
Record the current state before making a production change and keep a tested rollback path.
Change one variable at a time. Preserve timestamps, logs and configuration evidence so the result can be explained afterward.
Use a pilot scope whenever possible and avoid broad service restarts, policy relaxations or destructive cleanup as a first diagnostic step.

Prerequisites

Known domain topology, administrative boundaries and privileged access method.
Current DNS, time synchronization and replication health for identity-related procedures.
Administrative access appropriate to the system being changed or diagnosed.
A clearly identified scope: affected users, systems, addresses, services and the time of the observed problem.
A maintenance or test window when the procedure can affect production traffic or availability.
A copy of the current configuration or other recovery material before any irreversible action.

Step-by-step procedure

Establish the baseline and scope

Before changing anything, reproduce the issue or document the requested change on a representative system. Record the affected users or services, exact time, current configuration, recent changes and a known-good comparison point. This baseline is the reference used to decide whether each later step improves the situation.

The scope and current state are documented well enough to reproduce or verify the procedure.

Create an Active Directory site that represents a real network location

Implement this requirement in a controlled scope: Create an Active Directory site that represents a real network location. Capture the previous value or configuration first, make the smallest change that satisfies the design, and validate the effective state rather than assuming that a saved setting is active. If the expected result is not obtained, stop, restore the previous state, and reassess before expanding the change.

Evidence for this area is explicit, reproducible and consistent with the intended design.

Associate its IP subnets

Implement this requirement in a controlled scope: associate its IP subnets. Capture the previous value or configuration first, make the smallest change that satisfies the design, and validate the effective state rather than assuming that a saved setting is active. If the expected result is not obtained, stop, restore the previous state, and reassess before expanding the change.

Evidence for this area is explicit, reproducible and consistent with the intended design.

Connect it to the replication topology

Implement this requirement in a controlled scope: connect it to the replication topology. Capture the previous value or configuration first, make the smallest change that satisfies the design, and validate the effective state rather than assuming that a saved setting is active. If the expected result is not obtained, stop, restore the previous state, and reassess before expanding the change.

Evidence for this area is explicit, reproducible and consistent with the intended design.

Verify that clients

Implement this requirement in a controlled scope: verify that clients. Capture the previous value or configuration first, make the smallest change that satisfies the design, and validate the effective state rather than assuming that a saved setting is active. If the expected result is not obtained, stop, restore the previous state, and reassess before expanding the change.

Evidence for this area is explicit, reproducible and consistent with the intended design.

Domain controllers select the expected site

Implement this requirement in a controlled scope: domain controllers select the expected site. Capture the previous value or configuration first, make the smallest change that satisfies the design, and validate the effective state rather than assuming that a saved setting is active. If the expected result is not obtained, stop, restore the previous state, and reassess before expanding the change.

Evidence for this area is explicit, reproducible and consistent with the intended design.

Validate the complete service

Repeat the original user, system or application workflow from the real source and verify the complete result, not only one command or one local check. Confirm that logs and monitoring show the expected behavior and that no temporary debug, bypass, test account, rule or maintenance setting remains enabled.

The end-to-end service works or the remaining failure is isolated to a clearly identified component.

Technical commands from the original procedure

These technical blocks are preserved byte-for-byte from the historical procedure and kept in their original order. Review names, addresses, paths and parameters before use.

Technical block 1

Get-ADReplicationSite -Filter * | Select-Object Name

Technical block 2

Get-ADReplicationSubnet -Filter * | Select-Object Name,Site,Location

Technical block 3

Get-ADReplicationSiteLink -Filter * | Select-Object Name,Cost,ReplicationFrequencyInMinutes,SitesIncluded

Technical block 4

New-ADReplicationSite -Name "PARIS-SIEGE"

Technical block 5

Get-ADReplicationSite -Identity "PARIS-SIEGE"

Technical block 6

New-ADReplicationSubnet -Name "192.168.50.0/24" -Site "PARIS-SIEGE" -Location "Paris - Headquarters"

Technical block 7

Get-ADReplicationSubnet -Identity "192.168.50.0/24" | Format-List Name,Site,Location

Technical block 8

Get-ADReplicationSiteLink -Filter * | Format-Table Name,Cost,ReplicationFrequencyInMinutes

Technical block 9

New-ADReplicationSiteLink -Name "PARIS-HQ" -SitesIncluded "Default-First-Site-Name","PARIS-SIEGE" -Cost 100 -ReplicationFrequencyInMinutes 15 -InterSiteTransportProtocol IP

Technical block 10

nltest /dsgetsite

Technical block 11

nltest /dsgetdc:contoso.local

Technical block 12

repadmin /replsummary

Technical block 13

repadmin /showrepl

Technical block 14

dcdiag /test:replications

Validation

The procedure is validated when:

The original symptom or change request has been tested end to end.
The effective configuration matches the intended design and no unexplained error remains in the relevant logs.
Temporary troubleshooting controls have been removed and monitoring remains normal.
The result, evidence and any follow-up action are documented.

Rollback

Restore the configuration, policy, binding, route, credential assignment or service state recorded in the baseline when the change does not meet its success criteria.
Remove temporary rules, test objects and diagnostic settings that were introduced only for the procedure.
After rollback, repeat the minimum health checks to confirm that the previous service level has been restored.

Troubleshooting / common errors

Identity failures often combine DNS, time, replication, permissions and cached credentials; test each layer separately.
When policy is involved, verify the effective user/computer context rather than only the configured object.
If the result changes between tests, compare source, destination, identity, time and policy context before changing additional settings.
If a command succeeds but the application still fails, continue at the next protocol or application layer instead of widening access.
If the expected evidence is missing, verify that logging, auditing and the test path actually cover the failing component.
If the change does not improve the measured symptom, restore the previous state and reassess the working hypothesis.

Official and vendor references preserved from the original procedure

https://learn.microsoft.com/en-us/training/modules/active-directory-site-replication/
https://learn.microsoft.com/en-us/powershell/module/activedirectory/new-adreplicationsite?view=windowsserver2025-ps
https://learn.microsoft.com/en-us/powershell/module/activedirectory/new-adreplicationsubnet?view=windowsserver2025-ps
https://learn.microsoft.com/en-us/powershell/module/activedirectory/new-adreplicationsitelink?view=windowsserver2025-ps

Adapt names, addresses, paths and parameters to your environment. Back up the configuration and test on a limited scope first.