#Requires -Version 5.1
<#
    JbTecWiz Support Centre -- generated fix script

    Fault : Event 5719 -- no domain controller available for the domain
    Fix   : Repair DC location
    Source: https://jbtecwiz.com/support/srv-netlogon-5719

    Run as     : Elevated PowerShell
    Expect     : 40 minutes
    Risk       : low
    Reversible : yes

    WHEN THIS IS THE RIGHT FIX
    It happens outside of boot, or users are seeing failures.

    HOW TO UNDO IT
    Remove-ADReplicationSubnet for anything you added in error.

    This script walks the fix one step at a time and asks before each
    one. Steps with no command are things you do yourself -- it prints
    those and waits. Run with -DryRun to print without executing.

    --------------------------------------------------------------------
    NO WARRANTY - USE AT YOUR OWN RISK

    This script is provided by JbTecWiz as-is and with no warranty of any
    kind, express or implied. You run it entirely at your own risk.

    JbTecWiz accepts no liability for any loss or damage arising from its
    use, including but not limited to data loss, downtime, or configuration
    changes that turn out to be wrong for your system.

    You are responsible for reading this script before running it, for
    satisfying yourself that it suits the machine in front of you, and for
    having a working backup first. Some steps cannot be undone.
    --------------------------------------------------------------------
#>

[CmdletBinding()]
param(
    # Print every step and command without running anything.
    [switch]$DryRun,
    # Do not ask before each step. Read the script first if you use this.
    [switch]$Unattended
)

$ErrorActionPreference = 'Stop'
$script:Failed = 0

function Write-Rule { param([string]$Text)
    Write-Host ''
    Write-Host ('-' * 70) -ForegroundColor DarkGray
    if ($Text) { Write-Host $Text -ForegroundColor Cyan }
}

function Show-Prose { param([string]$Text, [string]$Colour = "Gray")
    if (-not $Text) { return }
    $words = $Text -split "\s+"; $line = "  "
    foreach ($w in $words) {
        if (($line.Length + $w.Length) -gt 74) { Write-Host $line -ForegroundColor $Colour; $line = "  " }
        $line += "$w "
    }
    if ($line.Trim()) { Write-Host $line -ForegroundColor $Colour }
}

function Invoke-Step {
    param(
        [int]$Number, [string]$Do, [string]$Why,
        [scriptblock]$Command, [switch]$Manual, [string]$Shell = "powershell"
    )
    Write-Rule "  Step $Number of 6"
    Show-Prose $Do "White"
    if ($Why) { Write-Host ""; Show-Prose $Why "DarkGray" }

    if ($Manual) {
        Write-Host ''
        Write-Host '  -> Do this yourself, then press Enter to carry on.' -ForegroundColor Yellow
        if (-not $Unattended -and -not $DryRun) { [void](Read-Host) }
        return
    }

    Write-Host ''
    foreach ($l in ($Command.ToString().Trim() -split "`n")) {
        Write-Host ("    " + $l.Trim()) -ForegroundColor Green
    }
    Write-Host ''

    if ($DryRun) { Write-Host "  (dry run -- not executed)" -ForegroundColor DarkGray; return }
    if (-not $Unattended) {
        $a = Read-Host "  Run this step? [Y]es / [S]kip / [Q]uit"
        if ($a -match "^[Qq]") { Write-Host "  Stopped at your request."; exit 0 }
        if ($a -match "^[Ss]") { Write-Host "  Skipped." -ForegroundColor DarkGray; return }
    }
    try { & $Command }
    catch {
        $script:Failed++
        Write-Host ("  Step $Number failed: " + $_.Exception.Message) -ForegroundColor Red
        Show-Prose "The rest of the fix may depend on this. Read the write-up before carrying on." "Red"
        if (-not $Unattended) {
            $c = Read-Host "  Carry on anyway? [y/N]"
            if ($c -notmatch "^[Yy]") { exit 1 }
        }
    }
}

Write-Rule
Write-Host '  Event 5719 -- no domain controller available for the domain' -ForegroundColor White
Write-Host '  Repair DC location' -ForegroundColor Cyan
Write-Host ''
Write-Host '  Risk: low   Reversible   40 minutes'
Write-Host ''
Show-Prose 'No warranty. Use at your own risk - JbTecWiz accepts no liability. Read it before you run it, and have a backup.' 'DarkYellow'
Write-Rule

if (-not $Unattended -and -not $DryRun) {
    $go = Read-Host '  Ready? [y/N]'
    if ($go -notmatch "^[Yy]") { Write-Host "  Nothing was changed."; exit 0 }
}

Invoke-Step -Number 1 -Do 'Ask the machine to locate a DC and show its reasoning.' -Command {
    nltest /dsgetdc:example.local /force
    nltest /dsgetsite
}

Invoke-Step -Number 2 -Do 'Check the DNS servers configured -- a public resolver here breaks DC location entirely.' -Command {
    Get-DnsClientServerAddress -AddressFamily IPv4 | Format-Table InterfaceAlias, ServerAddresses -AutoSize
}

Invoke-Step -Number 3 -Do 'Confirm the SRV records exist.' -Command {
    Resolve-DnsName -Name _ldap._tcp.dc._msdcs.example.local -Type SRV | Format-Table Name, NameTarget, Port -AutoSize
}

Invoke-Step -Number 4 -Do 'Check the client''s subnet is defined in Sites and Services -- an undefined subnet sends clients to a random site.' -Why 'A missing subnet definition makes clients authenticate across a WAN link to whichever DC answers first, which produces intermittent 5719s and slow logons that look like a network fault.' -Command {
    Get-ADReplicationSubnet -Filter * | Format-Table Name, Site -AutoSize
}

Invoke-Step -Number 5 -Do 'Add the missing subnet.' -Command {
    New-ADReplicationSubnet -Name '10.20.0.0/24' -Site 'Branch-Office'
}

Invoke-Step -Number 6 -Do 'Reset the secure channel if it is broken.' -Command {
    Test-ComputerSecureChannel -Repair -Credential (Get-Credential)
}

Write-Rule "  Confirm it worked"
Show-Prose 'nltest /dsgetdc returns a DC in the expected site, quickly.' 'White'
Write-Host ''
if (-not $DryRun) {
    nltest /dsgetdc:example.local
}

Write-Rule
if ($script:Failed -gt 0) {
    Write-Host ("  Finished with " + $script:Failed + " failed step(s).") -ForegroundColor Yellow
    Show-Prose 'Read the full write-up at https://jbtecwiz.com/support/srv-netlogon-5719' 'Yellow'
} else {
    Write-Host '  Finished.' -ForegroundColor Green
}
Write-Host ''
Show-Prose 'To undo: Remove-ADReplicationSubnet for anything you added in error.' 'DarkGray'
Write-Rule