How to check if an IP address is within a particular subnet

Question

I have a subnet in the format 10.132.0.0/20 and an IP address from the ASP.Net request object.

Is there a .NET framework function to check to see if the IP address i

Answer 1

I have also created a class which calculates the network and broadcast address and checks if the IP is neither broadcast nor network address.

private static IPValidationFailedReason PerformIPRangeValidation(string ipAddress, string subnetMask)
        {
            IPValidationFailedReason ipValidationType = IPValidationFailedReason.None;
            string networkaddress = string.Empty;
            string broadcastAddress = string.Empty;
            string networkAddressBinary = string.Empty;
            string broadcastAddressBinary = string.Empty;
            int zerosCountInSubnetMask = 0;

            Array.ForEach(subnetMask.Split(SplitterChar), (eachOctet) => Array.ForEach(IPInterfaceHelper.GetOctetWithPadding(eachOctet).Where(c => c == CharZero).ToArray(), (k) => zerosCountInSubnetMask++));

            if (zerosCountInSubnetMask == 0)
            {
                return ipValidationType;
            }

            string ipAddressBinary = IPInterfaceHelper.ToBinary(ipAddress);
            networkAddressBinary = GetNetworkAddressInBinaryFormat(zerosCountInSubnetMask, ipAddressBinary);
            broadcastAddressBinary = GetBroadcastAddressInBinaryFormat(zerosCountInSubnetMask, ipAddressBinary);

            networkaddress = ToIPFromBinary(networkAddressBinary);
            broadcastAddress = ToIPFromBinary(broadcastAddressBinary);

            if (ipAddress == networkaddress)
            {
                ipValidationType = IPValidationFailedReason.NetworkAddressZero;
                return ipValidationType;
            }
            if (ipAddress == broadcastAddress)
            {
                ipValidationType = IPValidationFailedReason.BroadcastAddressNotPermiited;
                return ipValidationType;
            }

            return ipValidationType;
        }


private static string GetNetworkAddressInBinaryFormat(int zeroCountInSubnetMask, string ipAddressBinary)
    {
        string networkAddressBinary = string.Empty;
        int countOfOnesInSubnetMask = TotalBitCount - zeroCountInSubnetMask;
        StringBuilder sb = new StringBuilder(ipAddressBinary);
        //When Subnet is like 255.255.255.0
        if (zeroCountInSubnetMask >= 1 && zeroCountInSubnetMask <= 8)
        {
            networkAddressBinary = sb.Replace(CharOne, CharZero, countOfOnesInSubnetMask + 3, zeroCountInSubnetMask).ToString();
        }
        //When Subnet is like 255.255.0.0
        if (zeroCountInSubnetMask > 8 && zeroCountInSubnetMask <= 16)
        {
            networkAddressBinary = sb.Replace(CharOne, CharZero, countOfOnesInSubnetMask + 2, zeroCountInSubnetMask + 1).ToString();
        }
        //When Subnet is like 255.0.0.0
        if (zeroCountInSubnetMask > 16 && zeroCountInSubnetMask <= 24)
        {
            networkAddressBinary = sb.Replace(CharOne, CharZero, countOfOnesInSubnetMask + 1, zeroCountInSubnetMask + 2).ToString();
        }
        //When Subnet is like 128.0.0.0
        if (zeroCountInSubnetMask > 24 && zeroCountInSubnetMask < 32)
        {
            networkAddressBinary = sb.Replace(CharOne, CharZero, countOfOnesInSubnetMask , zeroCountInSubnetMask + 3).ToString();
        }
        return networkAddressBinary;
    }


 private static string GetBroadcastAddressInBinaryFormat(int zeroCountInSubnetMask, string ipAddressBinary)
    {
        string broadcastAddressBinary = string.Empty;
        int countOfOnesInSubnetMask = TotalBitCount - zeroCountInSubnetMask;
        StringBuilder sb = new StringBuilder(ipAddressBinary);
        //When Subnet is like 255.255.255.0
        if (zeroCountInSubnetMask >= 1 && zeroCountInSubnetMask <= 8)
        {
            broadcastAddressBinary = sb.Replace(CharZero, CharOne, countOfOnesInSubnetMask + 3, zeroCountInSubnetMask).ToString();
        }
        //When Subnet is like 255.255.0.0
        if (zeroCountInSubnetMask > 8 && zeroCountInSubnetMask <= 16)
        {
            broadcastAddressBinary = sb.Replace(CharZero, CharOne, countOfOnesInSubnetMask + 2, zeroCountInSubnetMask + 1).ToString();
        }
        //When Subnet is like 255.0.0.0
        if (zeroCountInSubnetMask > 16 && zeroCountInSubnetMask <= 24)
        {
            broadcastAddressBinary = sb.Replace(CharZero, CharOne, countOfOnesInSubnetMask + 1, zeroCountInSubnetMask + 2).ToString();
        }
        //When Subnet is like 128.0.0.0
        if (zeroCountInSubnetMask > 24 && zeroCountInSubnetMask < 32)
        {
            broadcastAddressBinary = sb.Replace(CharZero, CharOne, countOfOnesInSubnetMask , zeroCountInSubnetMask + 3).ToString();
        }
        return broadcastAddressBinary;
    }

private static string ToIPFromBinary(string ipAddressBinary)
        {
            string addrTemp = string.Empty;
            string[] networkAddressBinaryOctets = ipAddressBinary.Split(SplitterChar);
            foreach (var eachOctet in networkAddressBinaryOctets)
            {
                string temp = Convert.ToUInt32(eachOctet, 2).ToString(CultureInfo.InvariantCulture);
                addrTemp += temp + SplitterChar;
            }
            // remove last '.'
            string ipAddress = addrTemp.Substring(0, addrTemp.Length - 1);
            return ipAddress;
        }