Calculating all addresses within a subnet…for IPv6

Question

I have seen plenty of great C# examples which demonstrate how to convert IPv4 addresses provided in CIDR notation (e.g. 192.168.0.1/25) into their relevant ranges (192.168.0

Answer 1

exNetworkLibrary is a great tool but if you can't use it in your project then you may just want to see this article:

http://www.codeproject.com/Articles/112020/IP-Address-Extension

It outlines how address masks are calculated for use in IPv4.

Your question is related to IPv6 I see and Since .Net 4.5 there is a IPAddress.MapToIPv6 method.

https://msdn.microsoft.com/en-us/library/system.net.ipaddress.maptoipv6(v=vs.110).aspx

You can utilize that with the checks in the article to produce this code:

    private static IPAddress empty = IPAddress.Parse("0.0.0.0");
    private static IPAddress intranetMask1 = IPAddress.Parse("10.255.255.255");
    private static IPAddress intranetMask2 = IPAddress.Parse("172.16.0.0");
    private static IPAddress intranetMask3 = IPAddress.Parse("172.31.255.255");
    private static IPAddress intranetMask4 = IPAddress.Parse("192.168.255.255");

    /// 

    /// Retuns true if the ip address is one of the following
    /// IANA-reserved private IPv4 network ranges (from http://en.wikipedia.org/wiki/IP_address)
    ///  Start        End   
    ///  10.0.0.0       10.255.255.255  
    ///  172.16.0.0       172.31.255.255    
    ///  192.168.0.0   192.168.255.255 
    /// 
    /// 
    public static bool IsOnIntranet(this IPAddress ipAddress)
    {
        if (empty.Equals(ipAddress))
        {
            return false;
        }

        bool onIntranet = IPAddress.IsLoopback(ipAddress);

        if (false == onIntranet)
        {
            //Handle IPv6 by getting the IPv4 Mapped Address. 
            if (ipAddress.AddressFamily == AddressFamily.InterNetworkV6)
            {
                onIntranet = ipAddress.Equals(ipAddress.And(intranetMask1.MapToIPv6())); //10.255.255.255
                onIntranet = onIntranet || ipAddress.Equals(ipAddress.And(intranetMask4.MapToIPv6())); ////192.168.255.255

                onIntranet = onIntranet || (intranetMask2.Equals(ipAddress.And(intranetMask2.MapToIPv6()))
                  && ipAddress.Equals(ipAddress.And(intranetMask3.MapToIPv6())));
            }
            else
            {
                onIntranet = ipAddress.Equals(ipAddress.And(intranetMask1)); //10.255.255.255
                onIntranet = onIntranet || ipAddress.Equals(ipAddress.And(intranetMask4)); ////192.168.255.255

                onIntranet = onIntranet || (intranetMask2.Equals(ipAddress.And(intranetMask2))
                  && ipAddress.Equals(ipAddress.And(intranetMask3)));
            }


        }

        return onIntranet;
    }

private static void CheckIPVersion(IPAddress ipAddress, IPAddress mask, out byte[] addressBytes, out byte[] maskBytes)
    {
        if (mask == null)
        {
            throw new ArgumentException();
        }

        addressBytes = ipAddress.GetAddressBytes();
        maskBytes = mask.GetAddressBytes();

        if (addressBytes.Length != maskBytes.Length)
        {
            throw new ArgumentException("The address and mask don't use the same IP standard");
        }
    }

    public static IPAddress And(this IPAddress ipAddress, IPAddress mask)
    {
        byte[] addressBytes;
        byte[] maskBytes;
        CheckIPVersion(ipAddress, mask, out addressBytes, out maskBytes);

        byte[] resultBytes = new byte[addressBytes.Length];
        for (int i = 0, e = addressBytes.Length; i < e; ++i)
        {
            resultBytes[i] = (byte)(addressBytes[i] & maskBytes[i]);
        }

        return new IPAddress(resultBytes);
    }