Remove PXE from HyperV Boot order

My VMs flood the network when PXE boots. Not sure of why, but to keep security happy I have removed the network boot via powershell.

$GetVM = Get-VM
Foreach ($vm in $GetVM)
{

Write-Host "Removing PXE from $($vm.Name)"
$old_boot_order = Get-VMFirmware -VMName $($vm.Name) | Select-Object -ExpandProperty BootOrder


$new_boot_order = $old_boot_order | Where-Object { $_.BootType -ne "Network" }

Set-VMFirmware -VMName $($vm.Name) -BootOrder $new_boot_order

}