validates ip by format and blacklists

validate_ip.rb

def ip_valid?(ip_str)
  begin
    ip = IPAddr.new(ip_str).to_i
  rescue
    return false
  end

  blacklist_ranges = [
    ['0.0.0.0', '0.255.255.255'],
    ['10.0.0.0', '10.255.255.255'],
    ['127.0.0.1', '127.255.255.255'],
    ['172.16.0.0', '172.31.255.255'],
    ['192.168.0.0', '192.168.255.255'],
  ].freeze

  blacklist_ranges.each do |ip_start, ip_end|
    low = IPAddr.new(ip_start).to_i
    high = IPAddr.new(ip_end).to_i
    return false if (low..high) === ip
  end

  true
end