Create-SplitVPNTunnel.ps1

#Requires -RunAsAdministrator
# Creates split VPN tunnel using routing rules

# To find this, run:  Get-NetAdapter | select InterfaceDescription
# And paste the one that corresponds to your VPN client
$VPNInterfaceDescription = "PANGP Virtual Ethernet Adapter"

# This is the subnet you want to route to the VPN; all other traffic will be through local connection
$SplitVPNSubnet = "10.2.0.0/16"


$VPNInterfaceIndex = (
    Get-NetAdapter -ErrorAction Stop | ? {
         $_.InterfaceDescription -eq $VPNInterfaceDescription
    }).ifIndex
    
try {

    $VPNGatewayIPv4 = [String](
        Get-NetIPConfiguration -ErrorAction Stop -InterfaceIndex $VPNInterfaceIndex
        ).IPv4Address
} catch {
    Write-Host "[-] Could not find VPN default gateway address, is VPN on?"
    exit 0
}


try {

$SNIArgs = @{
	InterfaceIndex = $VPNInterfaceIndex
	InterfaceMetric = 51
}
Set-NetIPInterface @SNIArgs


$SNArgs = @{
    DestinationPrefix = "0.0.0.0/0"
    RouteMetric = 100
    InterfaceIndex = $VPNInterfaceIndex
    ErrorAction = "Ignore"
}
if (! $(Get-NetRoute @SNArgs)){
    Set-NetRoute @SNArgs
} else {
	Write-Host "skipping set netroute"
}


$NNArgs = @{
    DestinationPrefix = $SplitVPNSubnet
    RouteMetric = 50
    InterfaceIndex = $VPNInterfaceIndex
    NextHop = $VPNGatewayIPv4
    ErrorAction = "Ignore"
}
if (! $(Get-NetRoute @NNArgs)){
    New-NetRoute @NNArgs
} else {
	Write-Host "skipping new netroute"
}

} catch {
    Write-host "[-] Could not create split VPN tunnel, are you administrator?"
    exit 1
}