Search GC replicas and find AD account - powershell

Question

I have an issue which is to do with AD replication. We use a 3rd party app the create accounts in AD and then a powershell script (called by the app) to create the exchange accounts.
In the 3rd party app we can not tell which GC the ad account has been created on and therefore have to wait 20 minutes for replication to happen.
What I am trying to do is find which GC the account has been created on or is replicated to and connect to that server using....
set-adserversettings -preferredserver $ADserver
I currently have the below script and what I can't work out is to get it to stop when it finds the account and assign that GC to the $ADserver variable. The write-host line is only there for testing.
$ForestInfo = [System.DirectoryServices.ActiveDirectory.Forest]::GetCurrentForest()
$GCs = $ForestInfo.FindAllGlobalCatalogs()
Import-module activedirectory
ForEach ($GC in $GCs)
{
Write-Host $GC.Name
Get-aduser $ADUser
}
TIA
Andy

Answer 1

You can check whether Get-ADUser returns more than 0 objects to determine whether the GC satisfied your query. After that, use Set-ADServerSettings -PreferredGlobalCatalog to configure the preference
You will need to specify that you want to search the Global Catalog and not just the local directory. The Global Catalog is accessible from port 3268 on the DC, so it becomes something like:
$ForestInfo = [System.DirectoryServices.ActiveDirectory.Forest]::GetCurrentForest()
$GCs = $ForestInfo.FindAllGlobalCatalogs()
Import-module ActiveDirectory
$ADUserName = "someusername"
$ADDomainDN = "DC=child,DC=domain,DC=tld"
$FinalGlobalCatalog = $null
foreach ($GC in $GCs)
{
$GCendpoint = "{0}:3268" -f $GC.Name
$SearchResult = Get-ADUser -LDAPFilter "(&(samaccountname=$ADUserName))" -Server $GCEndpoint -SearchBase $ADDomainDN -ErrorAction SilentlyContinue
if(#($SearchResult).Count -gt 0){
$FinalGlobalCatalog = $GC
break
}
}
if($FinalGlobalCatalog){
Write-Host "Found one: $($FinalGlobalCatalog.Name)"
Set-ADServerSettings -PreferredGlobalCatalog $FinalGlobalCatalog.Name
} else {
Write-Host "Unable to locate GC replica containing user $ADUserName"
}