auto_default_gateway_metric.ps1

function ipChangeHandler {
    Write-Host "Detected an IP change..."
    Write-Host "Collecting connections information..."
    $connObjs = New-Object System.Collections.ArrayList
    $ints = Get-NetIPAddress -AddressFamily IPv4 -PrefixOrigin Dhcp -AddressState Preferred
    foreach ($int in $ints) {
        $_alias = $int.InterfaceAlias
        $_index = $int.InterfaceIndex
        $_ipaddr = $int.IPAddress
        $intCfg = $int | Get-NetIPConfiguration
        $_gateway = $intCfg.IPv4DefaultGateway.NextHop
        $intAdp = Get-WmiObject -Class Win32_NetworkAdapter | where InterfaceIndex -EQ $_index | select InterfaceIndex, Speed
        $_linkspeed = $intAdp.Speed / 1000000
        $_free = "" -ne ((ping -n 1 -S $_ipaddr 8.8.8.8) -like "*Received = 1*")

        $connObjs.Add([PSCustomObject]@{
            InterfaceAlias = $_alias;
            IPAddress = $_ipaddr;
            Gateway = $_gateway;
            LinkSpeedMB = $_linkspeed;
            Free = $_free;
        }) > $null
    }

    if (0 -eq @($connObjs | where Free -EQ $true).Count) {
        Write-Host "No internet connnection detected. Resetting default gateway metric..."
        Set-NetRoute -DestinationPrefix 0.0.0.0/0 -RouteMetric 0 -Confirm:$false
    }
    else {
        Write-Host "Setting default gateway metric to max..."
        Set-NetRoute -DestinationPrefix 0.0.0.0/0 -RouteMetric 10000 -Confirm:$false

        $connObjs | where Free -EQ $true | foreach {
            Write-Host ("Setting route metric on " + $_.Gateway + "...")
            Get-NetRoute -DestinationPrefix 0.0.0.0/0 -NextHop $_.Gateway -InterfaceAlias $_.InterfaceAlias | Set-NetRoute -RouteMetric 1
        }

        Write-Host "Cycle completed."
    }
    
    $connObjs = $null;
    $ints = $null;

    Write-Host;
}


Unregister-Event -SourceIdentifier ADGWM_Timer -ErrorAction Ignore;
$timer = New-Object System.Timers.Timer -Property @{ Interval=5000; AutoReset=$false };
Register-ObjectEvent $timer -EventName Elapsed -SourceIdentifier ADGWM_Timer -Action { ipChangeHandler } > $null;


Write-Host "Registering for IP change event..."
Unregister-Event -SourceIdentifier ADGWM_IPChange -ErrorAction Ignore;
$networkChange = [System.Net.NetworkInformation.NetworkChange];
Register-ObjectEvent -InputObject $networkChange -EventName NetworkAddressChanged -SourceIdentifier ADGWM_IPChange -Action {
    $timer.Stop();
    $timer.Start();
} > $null;


<#
#check if no default gateway is present
Write-Host "Checking if no default gateway is present..."
if (0 -eq @(Get-NetRoute -DestinationPrefix 0.0.0.0/0 -ErrorAction Ignore).Count) {
    $theOne = $connObjs | sort LinkSpeedMB -Descending | select -First 1
    New-NetRoute -DestinationPrefix 0.0.0.0/0 -NextHop $theOne.Gateway -InterfaceAlias $theOne.InterfaceAlias -PolicyStore ActiveStore > $null
}
#>