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

    Fault : NTDS events 2087 and 2088 -- DNS lookup failure caused replication to fail
    Fix   : Repair the DNS records the DCs use to find each other
    Source: https://jbtecwiz.com/support/srv-ntds-2087

    Run as     : Elevated PowerShell
    Expect     : 30 minutes
    Risk       : low
    Reversible : yes

    WHEN THIS IS THE RIGHT FIX
    Either event is present. Treat 2088 with the same urgency as 2087 -- it
    is the same fault, currently masked by a fallback.

    HOW TO UNDO IT
    None -- this removes records that should not exist and recreates ones
    that should.

    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 5"
    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 '  NTDS events 2087 and 2088 -- DNS lookup failure caused replication to fail' -ForegroundColor White
Write-Host '  Repair the DNS records the DCs use to find each other' -ForegroundColor Cyan
Write-Host ''
Write-Host '  Risk: low   Reversible   30 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 'Run the DNS test and read the failures rather than the summary.' -Command {
    dcdiag /test:dns /v /e
}

Invoke-Step -Number 2 -Do 'On each DC, re-register its records.' -Command {
    ipconfig /registerdns
    nltest /dsregdns
    Restart-Service Netlogon
}

Invoke-Step -Number 3 -Do 'Check for stale records belonging to decommissioned DCs and delete them.' -Why 'A CNAME pointing at a DC that no longer exists makes replication attempts hang and then fail, and dcdiag reports it as a lookup failure.' -Command {
    Get-DnsServerResourceRecord -ZoneName '_msdcs.example.local' -RRType CName | Format-Table HostName, RecordData -AutoSize
}

Invoke-Step -Number 4 -Do 'Confirm scavenging is enabled so stale records do not accumulate again.' -Command {
    Get-DnsServerScavenging
}

Invoke-Step -Number 5 -Do 'Force replication.' -Command {
    repadmin /syncall /AdeP
}

Write-Rule "  Confirm it worked"
Show-Prose 'dcdiag passes and neither event recurs.' 'White'
Write-Host ''
if (-not $DryRun) {
    dcdiag /test:dns
    repadmin /replsummary
}

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-ntds-2087' 'Yellow'
} else {
    Write-Host '  Finished.' -ForegroundColor Green
}
Write-Host ''
Show-Prose 'To undo: None -- this removes records that should not exist and recreates ones that should.' 'DarkGray'
Write-Rule