def cidr=(newval)
      new_end = IPAddr.new("#{@starting_address}/#{newval}").to_range.end.mask 32
      self.class.validate_ip_range(@starting_address, new_end)
      @ending_address = new_end
      @need_to_update = true
    end
def cidr=(newval)
      new_end = IPAddr.new("#{@starting_address}/#{newval}").to_range.end.mask 32
      self.class.validate_ip_range(@starting_address, new_end)
      @ending_address = new_end
      @need_to_update = true
    end
set the ending address by applying a new cidr (e.g. 24)
 or mask (e.g. 255.255.255.0)

 @param newval[String, Integer] the new cidr or mask

 @return [void]