I have been looking around quite a bit to find some C# code to convert a network in CIDR notation (72.20.10.0/24) to an IP address range, without much luck. There are some threads about CIDR on stackoverlow, but none seems to have any C# code and cover exactly what I need. So I decided to cook it myself, and I did not want the code to rely on System.Net for any conversions in this version.
Perhaps it may be of help to someone.
References:
What's the best way to convert from network bitcount to netmask?
"Whatmask" C code from http://www.laffeycomputer.com/whatmask.html
Usage:
uint startIP, endIP;
Network2IpRange("72.20.10.0/24", out startIP, out endIP);
The code assumes 32 bits for everything.
static void Network2IpRange(string sNetwork, out uint startIP, out uint endIP)
{
uint ip, /* ip address */
mask, /* subnet mask */
broadcast, /* Broadcast address */
network; /* Network address */
int bits;
string[] elements = sNetwork.Split(new Char[] { '/' });
ip = IP2Int(elements[0]);
bits = Convert.ToInt32(elements[1]);
mask = ~(0xffffffff >> bits);
network = ip & mask;
broadcast = network + ~mask;
usableIps = (bits >30)?0:(broadcast - network - 1);
if (usableIps <= 0)
{
startIP = endIP = 0;
}
else
{
startIP = network + 1;
endIP = broadcast - 1;
}
}
public static uint IP2Int(string IPNumber)
{
uint ip = 0;
string[] elements = IPNumber.Split(new Char[] { '.' });
if (elements.Length==4)
{
ip = Convert.ToUInt32(elements[0])<<24;
ip += Convert.ToUInt32(elements[1])<<16;
ip += Convert.ToUInt32(elements[2])<<8;
ip += Convert.ToUInt32(elements[3]);
}
return ip;
}
Feel free to submit your improvements.
I recommend to use the C# IPNetwork class from Github.
string net = "192.168.168.100/24";
IPNetwork ipnetwork = IPNetwork.Parse(net);
Console.WriteLine("Network : {0}", ipnetwork.Network);
Console.WriteLine("Netmask : {0}", ipnetwork.Netmask);
Console.WriteLine("Broadcast : {0}", ipnetwork.Broadcast);
Console.WriteLine("FirstUsable : {0}", ipnetwork.FirstUsable);
Console.WriteLine("LastUsable : {0}", ipnetwork.LastUsable);
Console.WriteLine("Usable : {0}", ipnetwork.Usable);
Console.WriteLine("Cidr : {0}", ipnetwork.Cidr);
It will ouput
Network : 192.168.168.0
Netmask : 255.255.255.0
Broadcast : 192.168.168.255
FirstUsable : 192.168.168.1
LastUsable : 192.168.168.254
Usable : 254
Cidr : 24
Have fun.
Here is how you do it for your example 72.20.10.0/24
,
Let Network
be 72.20.10.0
Mask
is ~((1 << (32-24)) - 1)
// or
Mask
is ~(0xFFFFFFFF >> 24)
0xFFFFFF00
StartIP is -- (Network & Mask)
;
72.20.10.0 & 0xFFFFFF00
EndIP is -- ((Network & Mask) | ~Mask)
;
(72.20.10.0 & 0xFFFFFF00) | 0x000000FF
This will be 72.20.10.0 -- 72.20.10.255
.
The steps would go like this for a network/maskBits
,
You compute the mask
in one of these two ways,
mask = ~((1 << (32 - maskBits)) - 1) // or,
mask = ~(0xFFFFFFFF >> maskBits)
then the range is,
StartIP = network
EndIP = network | ~mask
More precisely,
StartIP = network & mask
EndIP = (network & mask) | ~mask
Where,
<<
is bitwise left shift (without rollover)&
is bitwise AND, |
is bitwise OR, and ~
is bitwise INVERT.Here's how to convert CIDR notation to a range in T-SQL, from my blog post :
First pre-create this function in SQL Server (from http://www.stardeveloper.com).
CREATE FUNCTION [dbo].[ConvertIPToLong](@IP varchar(15))
RETURNS bigint
AS
BEGIN
DECLARE @Long bigint
SET @Long = CONVERT(bigint, PARSENAME(@IP, 4)) * 256 * 256 * 256 +
CONVERT(bigint, PARSENAME(@IP, 3)) * 256 * 256 +
CONVERT(bigint, PARSENAME(@IP, 2)) * 256 +
CONVERT(bigint, PARSENAME(@IP, 1))
RETURN (@Long)
END
This is a sample of T-SQL code I put together that will calculate the low and high IP ranges from a CIDR address. It's messy and I had to work around T-SQL's lack of bit shift operators.
Declare @CidrIP varchar(50)
Set @CidrIP = '10.100.60.55/28'
Select dbo.[ConvertIPToLong](left(@CidrIP, patindex('%/%' , @CidrIP) - 1)) & (cast(4294967295 as bigint) ^ (Power(2, 32 - Cast(substring(@CidrIP, patindex('%/%' , @CidrIP) + 1, 2) as int)) - 1)) as LowRange,
dbo.[ConvertIPToLong](left(@CidrIP, patindex('%/%' , @CidrIP) - 1)) & (cast(4294967295 as bigint) ^ (Power(2, 32 - Cast(substring(@CidrIP, patindex('%/%' , @CidrIP) + 1, 2) as int)) - 1)) + (Power(2, 32 - Cast(substring(@CidrIP, patindex('%/%' , @CidrIP) + 1, 2) as int)) - 1)
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