预留的网络位

Question

我如何才能找到该地址的网络部分保留的位数？

这是我在Java代码：

public static void main(String[] args) throws SocketException {
    Enumeration<NetworkInterface> ifaces;
    ifaces = NetworkInterface.getNetworkInterfaces();
    while (ifaces.hasMoreElements()) {
        NetworkInterface iface = ifaces.nextElement();
        System.out.println(iface);

        // loop through all of the (potential) IP addresses configured to use "iface"
        Enumeration<InetAddress> addresses = iface.getInetAddresses();

       // Showing teh value, either ipv4 or ipv6
      // and the number of bits reserved for the network portion of the address

        while (addresses.hasMoreElements()) {

            InetAddress address = addresses.nextElement();
            String hostAddress = address.getHostAddress();

            System.out.println("addr: " + address.);

            if (address instanceof Inet4Address && !address.isLoopbackAddress()) {
                System.out.println("IPv4: /" + hostAddress);
            }
            else if(address instanceof Inet6Address && !address.isLoopbackAddress()){
                System.out.println("IPv6: /" + hostAddress);
            }

        }

    }
}

输出的例子，我应该得到：

name:lo0 (lo0)
    IPv6: /fe80:0:0:0:0:0:0:1%lo0, 64 bits reserved for the network
    IPv6: /0:0:0:0:0:0:0:1%lo0, 128 bits reserved for the network
    IPv4: /127.94.0.1, 8 bits reserved for the network
    IPv4: /127.0.0.1, 8 bits reserved for the network

我如何获得每个MAC地址保留位数？

Answer 1

IP地址和MAC地址是两回事。

你想要的东西，你就需要为每个IP地址对应的子网掩码。这会告诉你一个IP位是网络部分。然而，你不能从一个InetAddress子网掩码，所以尽量使用NetworkInterface.getInterfaceAddresses()代替。 InterfaceAddress有getAddress()和getNetworkPrefixLength()方法：

返回此地址的InetAddress。

返回此地址的网络前缀长度。这也被称为IPv4地址的情况下子网掩码。典型的IPv4值将是8（255.0.0.0），16（255.255.0.0）或24（255.255.255.0）。

典型的IPv6值将是128（:: 1/128）或10（FE80 :: 203：BAFF：FE27：1243年至1210年）