Tech Blog

Here’s a brilliant PowerShell scipt to check what the DNS servers are set as accross the domain then change it:

$allservers = @()
$domainpcs = Get-ADComputer -Filter * -Properties operatingsystem | where {$_.operatingsystem -like "*Server*"} | sort name
foreach ($pc in $domainpcs)
{
    if (Test-Connection $pc.DNSHostName -Quiet)
    {
        $thisserver = $null
        $DNSsettings = $null


        $DNSsettings = Get-DnsClientServerAddress -CimSession $pc.DNSHostName | where {($_.AddressFamily -eq 2) -and ($_.InterfaceAlias -notlike "Loopback*") -and ($_.InterfaceAlias -notlike "isatap*") -and ($_.ServerAddresses -ne $null)} | select @{n='DNSServers';e={$_ | select -ExpandProperty serveraddresses}},InterfaceIndex
        $thisserver =  New-Object psobject -Property @{
                       Servername = $pc.Name
                       interfaceindex = $DNSsettings.interfaceindex[0]
                       DNSsetting1 = $DNSsettings.dnsservers[0]
                       DNSsetting2 = $DNSsettings.dnsservers[1]
                       DNSsetting3 = $DNSsettings.dnsservers[2]
        }


        $allservers += $thisserver
        $thisserver
    }
    
}




foreach ($server in $allservers)

{

        $newdns1 = $null
        $newdns2 = $null
        $newdns3 = $null

        $needchange = $false

        write-host $server.Servername -ForegroundColor Green

       $newdns1 = $server.dnssetting1
        $newdns2 = $server.dnssetting2
        $newdns3 = $server.dnssetting3

       write-host $newdns1 -ForegroundColor Red
       write-host $newdns2 -ForegroundColor Red
       write-host $newdns3 -ForegroundColor Red


    

       Switch ($server.DNSsetting1)
       {
           "10.5.1.4" {$newdns1 = "8.8.8.8";$needchange =$true}
           "10.5.1.5" {$newdns1 = "8.8.4.4";$needchange =$true}
           "10.5.1.6" {$newdns1 = "1.1.1.1";$needchange =$true}
       }

       Switch ($server.dnssetting2)
       {
           "10.5.1.4" {$newdns2 = "8.8.8.8";$needchange =$true}
           "10.5.1.5" {$newdns2 = "8.8.4.4";$needchange =$true}
           "10.5.1.6" {$newdns2 = "1.1.1.1";$needchange =$true}
       }

       Switch ($server.dnssetting3)
       {
           "10.5.1.4" {$newdns3 = "8.8.8.8";$needchange =$true}
           "10.5.1.5" {$newdns3 = "8.8.4.4";$needchange =$true}
           "10.5.1.6" {$newdns3 = "1.1.1.1";$needchange =$true}
       }


       write-host $newdns1 -ForegroundColor Cyan
       write-host $newdns2 -ForegroundColor Cyan
       write-host $newdns3 -ForegroundColor Cyan

       $needchange
       if ($needchange)
       {      
           Set-DnsClientServerAddress -cimsession $server.servername -InterfaceIndex $server.interfaceindex -ServerAddresses ($newdns1,$newdns2,$newdns3)  -whatif
       }
}