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

    Fault : Error 1722 -- the RPC server is unavailable
    Fix   : Open the endpoint mapper and the dynamic range
    Source: https://jbtecwiz.com/support/srv-rpc-1722

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

    WHEN THIS IS THE RIGHT FIX
    A firewall sits between the two machines.

    HOW TO UNDO IT
    Remove the TCP/IP Port value and restart NTDS to return to the dynamic
    range.

    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 '  Error 1722 -- the RPC server is unavailable' -ForegroundColor White
Write-Host '  Open the endpoint mapper and the dynamic range' -ForegroundColor Cyan
Write-Host ''
Write-Host '  Risk: medium   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 'Confirm port 135 is reachable.' -Command {
    Test-NetConnection -ComputerName DC02 -Port 135
}

Invoke-Step -Number 2 -Do 'Ask the endpoint mapper what is registered -- this proves RPC itself is answering.' -Command {
    cmd.exe /c 'portqry -n DC02 -e 135 -p TCP'
}

Invoke-Step -Number 3 -Do 'Open the dynamic range 49152-65535 TCP between the two hosts, in both directions.' -Why 'The endpoint mapper answers on 135 with a high port for the actual call. Opening only 135 produces exactly this symptom: the connection appears to start and then fails.' -Manual

Invoke-Step -Number 4 -Do 'If the firewall cannot take that range, pin AD replication to a single port instead and open just that.' -Why 'Do this on every DC and restart each. Pinning on some but not all produces failures that look random.' -Command {
    New-ItemProperty -Path 'HKLM:\SYSTEM\CurrentControlSet\Services\NTDS\Parameters' -Name 'TCP/IP Port' -Value 51000 -PropertyType DWord -Force
}

Invoke-Step -Number 5 -Do 'Restart Active Directory Domain Services on each DC you changed.' -Command {
    Restart-Service NTDS -Force
}

Write-Rule "  Confirm it worked"
Show-Prose 'Replication succeeds and the port test passes.' 'White'
Write-Host ''
if (-not $DryRun) {
    repadmin /replsummary
    Test-NetConnection -ComputerName DC02 -Port 51000
}

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-rpc-1722' 'Yellow'
} else {
    Write-Host '  Finished.' -ForegroundColor Green
}
Write-Host ''
Show-Prose 'To undo: Remove the TCP/IP Port value and restart NTDS to return to the dynamic range.' 'DarkGray'
Write-Rule