PowerShell Sites and Services

Check client subnet mapping and replication topology as separate parts of a site problem.

Lesson 2 min read Windows PowerShell 5.1 and PowerShell 7

Written and tested by Dhrub Bharali · Updated 02 October 2026

Overview

An AD subnet maps an IP range to a site. A client’s site influences service discovery. Compare the client’s actual IP address with configured subnets, then use nltest /dsgetsite to inspect its site association.

A missing or incorrect mapping can lead to remote DC selection, but discovery also depends on available records, reachable DCs and cached information. Do not assume an unmapped client chooses uniformly at random or that every slow logon is a subnet problem.

Site-link cost expresses relative path preference for intersite topology. Schedule and replication interval determine when a link can be used. Network reachability remains a separate requirement: changing a cost does not open a firewall or repair a WAN path.

Before changing topology, record the intended site, selected DC, replication partners and existing schedules. Compare with the network team’s current subnet inventory instead of copying an address range from an old diagram.

Inspect this example’s structure

Read the command and its supplied arguments. This example requires real PowerShell or its module; this diagram does not execute it.

[pscustomobject]@{
  Sites = 'Get-ADReplicationSite -Filter *'
  Subnets = 'Get-ADReplicationSubnet -Filter * | Select-Object Name, Site'
  Links = 'Get-ADReplicationSiteLink -Filter * | Select-Object Name, Cost, ReplicationFrequencyInMinutes'
  Symptom = 'a subnet with no site sends clients to a random DC'
} | Format-List

Stage 1[pscustomobject]@{Positional values or no named parameters
Stage 2Format-ListPositional values or no named parameters

An example to inspect

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[pscustomobject]@{
  Sites = 'Get-ADReplicationSite -Filter *'
  Subnets = 'Get-ADReplicationSubnet -Filter * | Select-Object Name, Site'
  Links = 'Get-ADReplicationSiteLink -Filter * | Select-Object Name, Cost, ReplicationFrequencyInMinutes'
  Symptom = 'a subnet with no site sends clients to a random DC'
} | Format-List

What happens

These are inventory command strings. In a real investigation, compare their returned mappings with the affected client, then verify DC discovery and partner replication after the change.

Worth remembering

A correct subnet mapping is useful evidence, but verify client discovery and replication behavior as well.

Primary documentation

Microsoft Learn: get-adreplicationsubnet

Try it

Expected output · prints command text; does not execute these commands

1PS> [pscustomobject]@{

2PS> Sites = 'Get-ADReplicationSite -Filter *'

3PS> Subnets = 'Get-ADReplicationSubnet -Filter * | Select-Object Name, Site'

4PS> Links = 'Get-ADReplicationSiteLink -Filter * | Select-Object Name, Cost, ReplicationFrequencyInMinutes'

5PS> Symptom = 'a subnet with no site sends clients to a random DC'

6PS> } | Format-List

Example reader

Inspect this page's example

Fictional browser data when supported

Run supported commands against the practice data, or inspect the example without executing it.

[pscustomobject]@{
  Sites = 'Get-ADReplicationSite -Filter *'
  Subnets = 'Get-ADReplicationSubnet -Filter * | Select-Object Name, Site'
  Links = 'Get-ADReplicationSiteLink -Filter * | Select-Object Name, Cost, ReplicationFrequencyInMinutes'
  Symptom = 'a subnet with no site sends clients to a random DC'
} | Format-List

Ready to inspect.

Prints the site, subnet and site-link inventory queries.

Show reference output

Expected output · prints command text; does not execute these commands

Sites   : Get-ADReplicationSite -Filter *
Subnets : Get-ADReplicationSubnet -Filter * | Select-Object Name, Site
Links   : Get-ADReplicationSiteLink -Filter * | Select-Object Name, Cost, ReplicationFrequencyInMinutes
Symptom : a subnet with no site sends clients to a random DC

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