function Get-SubnetUsage {
    [CmdletBinding(DefaultParameterSetName="ByID")]
    param (
        [parameter(Mandatory=$true,ValueFromPipeline=$true,ValueFromPipelineByPropertyName=$true,Position=0,ParameterSetName="ByCIDR")]
        [ValidateScript({[ipaddress] $_.Split("/")[0] -and $_.Split("/")[1] -match "\d{1,2}"})]
        [ValidateNotNullOrEmpty()]
        [string]
        $CIDR,
        [parameter(Mandatory=$true,ValueFromPipeline=$true,ValueFromPipelineByPropertyName=$true,Position=0,ParameterSetName="ByID")]
        [ValidateScript({ $_ -match "^\d+$" })]
        [ValidateNotNullOrEmpty()]
        [string]
        $Id
    )
    process {
        $_params = @{
            Controller = "subnets"
            Method     = "GET"
        }
        switch ($PSCmdlet.ParameterSetName) {
            "ByCIDR"    {
                $_subnetId = (Get-Subnet -CIDR $CIDR).id
                if (!$_subnetId) { throw "Cannot find subnet!" }
                break
            }
            "ByID"      { $_subnetId = $Id; break }
        }
        $_identifiers = @($_subnetId,"usage")
        $_params.Add("Identifiers",$_identifiers)

        return Invoke-Request @_params
    }
}
Export-ModuleMember -Function Get-SubnetUsage