#Requires -Version 5.1
<#
    JbTecWiz Support Centre -- read-only diagnostic

    Fault : Websites do not load but the IP address pings -- DNS resolution failure
    Source: https://jbtecwiz.com/support/win-net-dns-only

    This script CHANGES NOTHING. It runs only the inspection commands
    from the write-up -- the Get-, Test- and Resolve- calls that
    establish which cause is in play -- and prints what each returned.
    Anything that writes, deletes, starts or stops is excluded by
    construction, not by judgement.

    Read the output alongside the write-up, then pick the fix that
    matches. Each fix has its own script on the same page.

    --------------------------------------------------------------------
    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([switch]$Transcript)
$ErrorActionPreference = 'Continue'

if ($Transcript) {
    $log = Join-Path $env:USERPROFILE ("jbtecwiz-win-net-dns-only-" + (Get-Date -Format yyyyMMdd-HHmmss) + ".txt")
    Start-Transcript -Path $log | Out-Null
    Write-Host ('  Saving a transcript to ' + $log)
}

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

function Probe { param([string]$Label, [string]$Fix, [scriptblock]$Command)
    Write-Rule ("  " + $Label)
    Write-Host ("  from: " + $Fix) -ForegroundColor DarkGray
    Write-Host ''
    foreach ($l in ($Command.ToString().Trim() -split "`n")) {
        Write-Host ("    " + $l.Trim()) -ForegroundColor DarkGreen
    }
    Write-Host ''
    try {
        $out = & $Command 2>&1 | Out-String
        if ([string]::IsNullOrWhiteSpace($out)) {
            Write-Host '    (returned nothing)' -ForegroundColor DarkGray
        } else {
            foreach ($l in ($out.TrimEnd() -split "`n")) { Write-Host ("    " + $l.TrimEnd()) }
        }
    } catch {
        Write-Host ("    could not run: " + $_.Exception.Message) -ForegroundColor Yellow
    }
}

Write-Rule
Write-Host '  Websites do not load but the IP address pings -- DNS resolution failure' -ForegroundColor White
Write-Host '  Read-only diagnostic -- nothing is changed.' -ForegroundColor Green
Write-Rule

Probe -Label 'Look at what is actually cached before clearing it -- this often names the culprit.' -Fix 'Clear the resolver cache and the poisoned entries in it' -Command {
    Get-DnsClientCache | Where-Object Entry -notlike '*.local' | Select-Object -First 30 Entry,Data,TimeToLive
}

Probe -Label 'Check the hosts file. An entry here beats DNS entirely and survives every cache flush.' -Fix 'Clear the resolver cache and the poisoned entries in it' -Command {
    Get-Content $env:WINDIR\System32\drivers\etc\hosts | Where-Object { $_ -notmatch '^\s*#' -and $_.Trim() }
}

Probe -Label 'Ask the configured server directly, then ask a public one, and compare.' -Fix 'Clear the resolver cache and the poisoned entries in it' -Command {
    Resolve-DnsName jbtecwiz.com
    Resolve-DnsName jbtecwiz.com -Server 1.1.1.1
}

Probe -Label 'Verify: Both queries return the same address and browsing works.' -Fix 'Clear the resolver cache and the poisoned entries in it' -Command {
    Resolve-DnsName outlook.office365.com | Select-Object -First 3 Name,Type,IPAddress
}

Probe -Label 'Test each configured server before changing anything.' -Fix 'Point the machine at DNS servers it can actually reach' -Command {
    Test-NetConnection 10.0.0.10 -Port 53 -InformationLevel Detailed
}

Probe -Label 'Verify: Names resolve and the internal ones still work if this is a domain machine.' -Fix 'Point the machine at DNS servers it can actually reach' -Command {
    Resolve-DnsName $env:USERDNSDOMAIN -Type SOA
}

Write-Rule
Write-Host '  Diagnostic finished. Nothing was changed.' -ForegroundColor Green
Write-Host ''
Write-Host '  Compare the output above with the write-up, then run the'
Write-Host '  script for the fix that matches:'
Write-Host '    https://jbtecwiz.com/support/win-net-dns-only'
Write-Rule
if ($Transcript) { Stop-Transcript | Out-Null }