Select the PowerShell cmdlet with basic syntax if you want to create a private network switch called HalifaxLAN and connect it to your VM's adapter named NSNet1.

New-VMSwitch “HalifaxLAN” -NetAdapterName “NSNet1” -SwitchType Private

New-VMSwitch “HalifaxLAN” -NetAdapterName “NSNet1” -SwitchType "Private"

New-Switch “HalifaxLAN” -NetAdapterName “NSNet1” -SwitchType "Private"

New-Switch “HalifaxLAN” -NetAdapterName “NSNet1” -SwitchType Private

https://technet.microsoft.com/en-us/itpro/powershell/windows/hyper-v/new-vmswitch

Create Hyper-V external VMSwitch with PowerShell

You can create Hyper-V VMSwitches very easely with Powershell since Hyper-V 2012 :

New-VMSwitch -NetAdapterName "Ethernet" -Name vEthExternal -AllowManagementOS $true
New-VMSwitch -Name 'vPrivate' -SwitchType Private
New-VMSwitch -Name 'vInternal' -SwitchType Internal

Hint : The first NIC of a computer is allways named “Ethernet”.

You can check the result with :

Get-VMSwitch