If you need to get all DHCP server leases within your network you could use Windows Server 2012 DHCP cmdlets for the task. You need to install the DHCP RSAT module on the server.

$dhcpservers= Get-DhcpServerInDC

$scope= @()

$reportdata= @()

$ping=new-object System.Net.NetworkInformation.Ping                 

foreach ($dhcpserverin$dhcpservers )

    {

        $reply=$null

        $Reply=$ping.send($dhcpserver.DnsName)        

        If ($reply.status -eq“Success”)

        {

$scopes= Get-DhcpServerv4Scope -ComputerName $dhcpserver.dnsname

        If ($scopes-ne$null)

            {

            foreach ($scopein$scopes)

                {

$Leases= Get-DhcpServerv4Lease -ScopeId $scope.ScopeId -ComputerName $dhcpserver.dnsname

                Foreach ($leasein$Leases) {

write-host$ Lease.IPAddress $Lease.HostName

$reportdata+=New-Object-TypeNamePSObject-Property @{

                    Server =$dhcpserver.dnsname

                    Scope =$Lease.ScopeId

                    IP =$Lease.IPAddress

                    Mac =$Lease.ClientID