get-reverseip.ps1

function Get-ReverseIP
{
[cmdletbinding()]
[OutputType([String[]])]
Param(
    [Parameter(
        ValueFromPipeline=$true,
        ValueFromPipelineByPropertyName=$true, 
        ValueFromRemainingArguments=$false, 
        Position=0)]
    [string[]]$Ipaddress
)

Begin
{
}

Process
{
    foreach($ip in $Ipaddress)
    {
        $IpArray = $ip -split "\."
        [array]::Reverse($IpArray)
        $IpArray -join "."
    }
}

End
{
}
}