How to see if an IP address belongs inside of a range of IPs using CIDR notation?

Question

Here I have a static reference the ranges I need to check:

private static List Ip_Range = new List()
{
    \"12.144.86.0/23\",
           


        

Answer 1

I use the below method to determine whether a given IP Address is a public one or private/internal:

private bool IsInternalIpAddress(string ipAddress)
    {
        // notes: http://whatismyipaddress.com/private-ip

        var internalIpRanges = Enumerable
            .Range(16, 31)
            .Select(i => "172.{0}.".FormatWith(i))
            .Concat(new[] {"192.168.", "10.", "127."})
            .ToArray();

        return ipAddress.StartsWith(internalIpRanges);
    }