protected function _validateIPv6($value) {
        if (strlen($value) < 3) {
            return $value == '::';
        }

        if (strpos($value, '.')) {
            $lastcolon = strrpos($value, ':');
            if (!($lastcolon && $this->_validateIPv4(substr($value, $lastcolon + 1)))) {
                return false;
            }

            $value = substr($value, 0, $lastcolon) . ':0:0';
        }

        if (strpos($value, '::') === false) {
            return preg_match('/\A(?:[a-f0-9]{1,4}:){7}[a-f0-9]{1,4}\z/i', $value);
        }

        $colonCount = substr_count($value, ':');
        if ($colonCount < 8) {
            return preg_match('/\A(?::|(?:[a-f0-9]{1,4}:)+):(?:(?:[a-f0-9]{1,4}:)*[a-f0-9]{1,4})?\z/i', $value);
        }

        // special case with ending or starting double colon
        if ($colonCount == 8) {
            return preg_match('/\A(?:::)?(?:[a-f0-9]{1,4}:){6}[a-f0-9]{1,4}(?:::)?\z/i', $value);
        }

        return false;
    }