Some friends here on the Hyper-V team shared a PowerShell 2.0 script for connecting your virtual switches to the management partition (parent partition):

# Connect a Virtual Switch to the management partition

param(
    [string]$vsName = $(throw "Must specify virtual switch name"),
    [string]$intEthName = [guid]::NewGuid().guid,
    [string]$switchPortName = [guid]::NewGuid().guid
)

$vSwitch = gwmi -namespace root\virtualization Msvm_VirtualSwitch -filter "ElementName = '$vsName'"
$vsms = gwmi -namespace root\virtualization Msvm_VirtualSwitchManagementService

# Create a new internal ethernet port
$result = $vsms.CreateInternalEthernetPortDynamicMac($intEthName,"Internal Ethernet Port")
if($result.ReturnValue -ne 0){
    return $result.ReturnValue
}
$intEthernet = [wmi]$result.CreatedInternalEthernetPort

# Create a new switch port on the virtual switch
$result = $vsms.CreateSwitchPort($vSwitch, $switchPortName, "Switch Port to Internal Ethernet", "")
if($result.ReturnValue -ne 0){
    return $result.ReturnValue
}
$switchPort = [wmi]$result.CreatedSwitchPort

# Get the endpoint connected to the internal ethernet port and
# connect it to the switch port
$endpoint = gwmi -namespace root\virtualization `
    -query "Associators of {$intEthernet} where ResultClass = Msvm_SwitchLANEndpoint"

$result = $vsms.ConnectSwitchPort($switchPort, $endpoint)

if($result.ReturnValue -eq 4096){
    # A Job was started, and can be tracked using its Msvm_Job instance
    $job = [wmi]$result.Job
    # Wait for job to finish
    while($job.jobstate -lt 7){$job.get()}
    # Return the Job's error code
    return $job.ErrorCode
}
# Otherwise, the method completed
return $result.ReturnValue

For more info on how to use PS cmdlets see: http://www.microsoft.com/technet/scriptcenter/topics/msh/cmdlets/index.mspx

See also James O’Neil’s New and improved PowerShell Library for Hyper-V. Now with more functions and... documentation!

For all 35 sample Hyper-V PS1 scripts in a zipfile, go to: Hyper-V PowerShell Example Scripts.zip-download