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<string> Ip_Range = new List<string>() {     "12.144.86.0/23",     "31.201.1.176/30",     "46.36.198.101/32",     "46.36.198.102/31",     "46.36.198.104/31",     "46.136.172.0/24",     "63.65.11.0/24",     "63.65.12.0/25",     "63.65.12.128/26",     "63.65.12.192/27",     "63.65.12.224/28",     "63.65.12.240/29",     "63.65.12.248/30",     "63.65.12.252/31",     "63.65.12.254/32",     "65.173.56.0/21",     "67.23.241.179/32",     "67.23.241.180/30",     "67.23.241.184/29",     "67.23.241.192/30",     "67.23.241.196/31",     "67.23.241.198/32",     "72.32.164.56/29",     "72.46.244.32/28",     "74.91.16.48/29",     "74.91.16.208/29",     "74.91.20.48/28",     "74.91.20.64/29",     "74.112.134.120/29",     "74.112.135.104/29",     "74.205.37.16/29",     "78.24.205.32/28",     "98.129.27.88/29",     "98.129.91.40/29",     "166.114.0.0/16",     "167.157.0.0/16",     "174.143.165.80/29",     "186.0.156.0/22",     "186.2.0.0/17",     "186.27.0.0/17",     "190.0.248.0/21",     "190.3.184.0/21" }; 

Here's some pseudo code on how I see it working:

public static bool IpIsWithinRange(string ip) //Something like 127.0.0.1 or 184.56.26.35 {     IPAddress incomingIp = IPAddress.Parse(ip);     foreach (var subnet in Ip_Range)     {         IPAddress sub = IPAddress.Parse(subnet); ?????         if (incomingIp "is in" sub) ?             return true;                 }     return false; } 

Any suggestions on how to code up this functionality?

Answer 1

If you don't want/can't add another library (as the IPnetwork one) to your project and just need to deal with IPv4 CIDR ranges, here's a quick solution to your problem

// true if ipAddress falls inside the CIDR range, example // bool result = IsInRange("10.50.30.7", "10.0.0.0/8"); private bool IsInRange(string ipAddress, string CIDRmask) {     string[] parts = CIDRmask.Split('/');      int IP_addr = BitConverter.ToInt32(IPAddress.Parse(ipAddress).GetAddressBytes(), 0);     int CIDR_addr = BitConverter.ToInt32(IPAddress.Parse(parts[0]).GetAddressBytes(), 0);     int CIDR_mask = IPAddress.HostToNetworkOrder(-1 << (32 - int.Parse(parts[1])));      return ((IP_addr & CIDR_mask) == (CIDR_addr & CIDR_mask)); } 

the above will allow you to quickly check if a given IPv4 address falls inside a given CIDR range; notice that the above code is barebone, it's up to you to check if a given IP (string) and CIDR range are correct before feeding them to the function (you may just use the tryparse or whatever...)

Answer 2

Decided to answer my own question so people can benefit. If it can be improved, please do!

I used the IPNetwork library and it worked out fantastically! Below is the code I used:

using System.Net;  public static class RedirectHelpers {     public static bool IpIsWithinBoliviaRange(string ip)     {         IPAddress incomingIp = IPAddress.Parse(ip);         foreach (var subnet in Bolivia_Ip_Range)         {             IPNetwork network = IPNetwork.Parse(subnet);              if (IPNetwork.Contains(network, incomingIp))                 return true;         }         return false;     }      private static List<string> Bolivia_Ip_Range = new List<string>()     {         "12.144.86.0/23",         "31.201.1.176/30",         "46.36.198.101/32",         "46.36.198.102/31",         "46.36.198.104/31",         "46.136.172.0/24",         "63.65.11.0/24",         "63.65.12.0/25",         "63.65.12.128/26",         "63.65.12.192/27",         "63.65.12.224/28",         "63.65.12.240/29",         "63.65.12.248/30",         "63.65.12.252/31",         "63.65.12.254/32",         "65.173.56.0/21",         "67.23.241.179/32",         "67.23.241.180/30",         "67.23.241.184/29",         "67.23.241.192/30",         "67.23.241.196/31",         "67.23.241.198/32",         "72.32.164.56/29",         "72.46.244.32/28",         "74.91.16.48/29",         "74.91.16.208/29",         "74.91.20.48/28",         "74.91.20.64/29",         "74.112.134.120/29",         "74.112.135.104/29",         "74.205.37.16/29",         "78.24.205.32/28",         "98.129.27.88/29",         "98.129.91.40/29",         "166.114.0.0/16",         "167.157.0.0/16",         "174.143.165.80/29",         "186.0.156.0/22",         "186.2.0.0/17",         "186.27.0.0/17",         "190.0.248.0/21",         "190.3.184.0/21",         "166.114.0.0/16",         "167.157.0.0/16",         "186.2.0.0/18",         "190.11.64.0/20",         "190.11.80.0/20",         "190.103.64.0/20",         "190.104.0.0/19",         "190.107.32.0/20",         "190.129.0.0/17",         "190.181.0.0/18",         "190.186.0.0/18",         "190.186.64.0/18",         "190.186.128.0/18",         "200.7.160.0/20",         "200.58.64.0/20",         "200.58.80.0/20",         "200.58.160.0/20",         "200.58.176.0/20",         "200.75.160.0/20",         "200.85.128.0/20",         "200.87.0.0/17",         "200.87.128.0/17",         "200.105.128.0/19",         "200.105.160.0/19",         "200.105.192.0/19",         "200.112.192.0/20",         "200.119.192.0/20",         "200.119.208.0/20",         "201.222.64.0/19",         "201.222.96.0/19"     }; }