How to Search Users Across Active Directory Domains in PowerShell (Global Search)

In large organizations with multiple domains, administrators need to identify users who have been moved across domains. This article explains two approaches.

Active Directory Infrastructure

The example uses a forest with three domain controllers:

• DC1.mike.com — Primary domain controller in mike.com domain
• DC2.child.mike.com — Global Catalog DC in child domain
• DC3.child.mike.com — Domain controller in child domain

Method 1: Active Directory Administrative Center (ADAC)

For single-user searches, ADAC provides the fastest approach:

1. Select “Global Catalog Search” in the GLOBAL SEARCH scope
2. Type the user’s name in the search box
3. Results use the ANR (Ambiguous Name Resolution) LDAP filter

Method 2: PowerShell Script

For batch operations, a PowerShell script is more efficient:

# Check samaccountname and list users not in the domain
$filepath = "C:\temp\shares"
$allfolders = Get-ChildItem -Directory -Path $filepath

$obj2 = @()
foreach ($folder in $allfolders) {
    try {
        if (Get-ADUser $folder.name -ErrorAction Stop) {
            $AD = "Y"
        }
    }
    catch [Microsoft.ActiveDirectory.Management.ADIdentityNotFoundException] {
        $AD = "N"
        $displayname = Get-ADObject -LDAPFilter "samaccountname=$($folder.name)" `
            -Server "dc1.mike.com:3268" -Properties * |
            Select-Object -ExpandProperty displayname
        $DistinguishedName = Get-ADObject -LDAPFilter "samaccountname=$($folder.name)" `
            -Server "dc1.mike.com:3268" -Properties * |
            Select-Object -ExpandProperty DistinguishedName

        $obj = [pscustomobject]@{
            ID                = $folder.Name
            Name              = $displayname
            DistinguishedName = $DistinguishedName
        }

        $obj2 += $obj
    }
}

$obj2 | Format-Table

# Export to CSV
$csvpath = "c:\temp\export.csv"
$obj2 | Export-Csv -Path $csvpath -NoTypeInformation

Key Details

• Line 11: Checks whether the user exists in the current domain using Get-ADUser
• Lines 17–18: For users not found, performs a global search
• Port 3268: The Global Catalog query uses this specific port (dc1.mike.com:3268), enabling cross-domain search functionality