Validate an IP Address (with Mask)

Question

I have ip addresses and a mask such as 10.1.1.1/32. I would like to check if 10.1.1.1 is inside that range. Is there a library or utility that would do

Answer 1

There is commons-ip-math library that I believe does a very good job. Please note that as of May 2019, there hasn't been any updates to the library for 2 years (Could be that its already very mature library). Its available on maven-central

It supports working with both IPv4 and IPv6 addresses. Their brief documentation has examples on how you can check if an address is in a specific range for IPv4 and IPv6

Example for IPv4 range checking:

        String input1 = "10.1.1.1";
        Ipv4 ipv41 = Ipv4.parse(input1);

        // Using CIDR notation to specify the networkID and netmask
        Ipv4Range range = Ipv4Range.parse("10.1.1.1/32");
        boolean result = range.contains(ipv41);
        System.out.println(result); //true

        String input2 = "10.1.1.1";
        Ipv4 ipv42 = Ipv4.parse(input2);

        // Specifying the range with a start and end.
        Ipv4 start = Ipv4.of("10.1.1.1");
        Ipv4 end = Ipv4.of("10.1.1.1");
        range = Ipv4Range.from(start).to(end);

        result = range.contains(ipv42); //true
        System.out.println(result);