好吧,我似乎无法想出解决办法:给出以下几点:给定一个IP地址和子网掩码,如何计算CIDR?
IP address = 192.168.1.0
Subnetmask = 255.255.255.240
使用C#,我该如何计算CIDR标记192.168.1.0/28
?有没有简单的方法来实现这一目标?我错过了什么吗?
谢谢!
好吧,我似乎无法想出解决办法:给出以下几点:给定一个IP地址和子网掩码,如何计算CIDR?
IP address = 192.168.1.0
Subnetmask = 255.255.255.240
使用C#,我该如何计算CIDR标记192.168.1.0/28
?有没有简单的方法来实现这一目标?我错过了什么吗?
谢谢!
我没有它作为C#代码,但这里是在VB中的答案。不应该难以转换。
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim someIP As Net.IPAddress = Net.IPAddress.Parse("192.168.1.10")
Dim someMASK As Net.IPAddress = Net.IPAddress.Parse("255.255.255.240")
Dim ipL As Long = IPtoLong(someIP)
Dim maskL As Long = IPtoLong(someMASK)
'Convert Mask to CIDR(1-30)
Dim oneBit As Long = &H80000000L
Dim CIDR As Integer = 0
For x As Integer = 31 To 0 Step -1
If (maskL And oneBit) = oneBit Then CIDR += 1 Else Exit For
oneBit = oneBit >> 1
Next
Dim answer As String = LongToIp(ipL And maskL) & " /" & CIDR.ToString
End Sub
Public Function IPtoLong(ByVal theIP As Net.IPAddress) As Long 'convert IP to number
Dim IPb() As Byte = theIP.GetAddressBytes 'get the octets
Dim addr As Long 'accumulator for address
For x As Integer = 0 To 3
addr = addr Or (CLng(IPb(x)) << (3 - x) * 8)
Next
Return addr
End Function
Public Function LongToIp(ByVal theIP As Long) As String 'convert number back to IP
Dim IPb(3) As Byte '4 octets
Dim addr As String = "" 'accumulator for address
Dim mask8 As Long = MaskFromCidr(8) 'create eight bit mask
For x = 0 To 3 'get the octets
IPb(x) = CByte((theIP And mask8) >> ((3 - x) * 8))
mask8 = mask8 >> 8
addr &= IPb(x).ToString & "." 'add current octet to string
Next
Return addr.TrimEnd("."c)
End Function
Private Function MaskFromCidr(ByVal CIDR As Integer) As Long
MaskFromCidr = CLng(2^((32 - CIDR)) - 1) Xor 4294967295L
End Function
256 - 240 = 16 = 2**4, 32 - 4 = 28
这是不是一个真正的C#问题。
要从IP和掩码获得网络地址,您可以将字节and
应用于IP和掩码。您可以使用IPAddress.Parse()
和IPAddress.GetAddressBytes()
从字符串中获取字节。
我必须做同样的事情,没有任何新的信息,但这个片段可以派上用场寻找一种方式,在C#这样做旁边的人。 请注意,这种方法只计算连续1的数量,并且让您将其附加到IP的工作。
public class IPAddressHelper
{
public static UInt32 SubnetToCIDR(string subnetStr)
{
IPAddress subnetAddress = IPAddress.Parse(subnetStr);
byte[] ipParts = subnetAddress.GetAddressBytes();
UInt32 subnet = 16777216 * Convert.ToUInt32(ipParts[0]) + 65536 * Convert.ToUInt32(ipParts[1]) + 256 * Convert.ToUInt32(ipParts[2]) + Convert.ToUInt32(ipParts[3]);
UInt32 mask = 0x80000000;
UInt32 subnetConsecutiveOnes = 0;
for (int i = 0; i < 32; i++)
{
if (!(mask & subnet).Equals(mask)) break;
subnetConsecutiveOnes++;
mask = mask >> 1;
}
return subnetConsecutiveOnes;
}
}
用法:
var cidrnetmask = MaskToCIDR(IPAddress.Parse("255.0.0.0").GetAddressBytes());
这适用于IPv4的。要支持IPv6,一个可以扩展的字节数,但希望没有人会尝试使用IPv6的旧式网络掩码:O)
方法:
static int MaskToCIDR(byte[] bytes)
{
var b0 = bytes[0];
var b1 = bytes[1];
var b2 = bytes[2];
var b3 = bytes[3];
return
b3 != 0 ? (
(b3 & 0x01) != 0 ? 32 :
(b3 & 0x02) != 0 ? 31 :
(b3 & 0x04) != 0 ? 30 :
(b3 & 0x08) != 0 ? 29 :
(b3 & 0x10) != 0 ? 28 :
(b3 & 0x20) != 0 ? 27 :
(b3 & 0x40) != 0 ? 26 :
25) :
b2 != 0 ? (
(b2 & 0x01) != 0 ? 24 :
(b2 & 0x02) != 0 ? 23 :
(b2 & 0x04) != 0 ? 22 :
(b2 & 0x08) != 0 ? 21 :
(b2 & 0x10) != 0 ? 20 :
(b2 & 0x20) != 0 ? 19 :
(b2 & 0x40) != 0 ? 18 :
17) :
b1 != 0 ? (
(b1 & 0x01) != 0 ? 16 :
(b1 & 0x02) != 0 ? 15 :
(b1 & 0x04) != 0 ? 14 :
(b1 & 0x08) != 0 ? 13 :
(b1 & 0x10) != 0 ? 12 :
(b1 & 0x20) != 0 ? 11 :
(b1 & 0x40) != 0 ? 10 :
9 ) :
b0 != 0 ? (
(b0 & 0x01) != 0 ? 8 :
(b0 & 0x02) != 0 ? 7 :
(b0 & 0x04) != 0 ? 6 :
(b0 & 0x08) != 0 ? 5 :
(b0 & 0x10) != 0 ? 4 :
(b0 & 0x20) != 0 ? 3 :
(b0 & 0x40) != 0 ? 2 :
1) :
0;
}
我的解决方法,首先解析到ip地址:
var Subnetmask = "255.255.255.240";
IPAddress ip = IPAddress.Parse(Subnetmask);
然后,检查组位计数在掩模IP:
var intAddress = (int)IPAddress.Address;
Console.WriteLine(NumberOfSetBits(intAddress)); //28
函数(从https://stackoverflow.com/a/12175897/1271037):
int NumberOfSetBits(int i)
{
i = i - ((i >> 1) & 0x55555555);
i = (i & 0x33333333) + ((i >> 2) & 0x33333333);
return (((i + (i >> 4)) & 0x0F0F0F0F) * 0x01010101) >> 24;
}
感谢您的信息。我知道我可以使用IPAddress类操纵字符串到IP地址和字节。我也理解子网/广播/ cidr计算等背后的逻辑...我只是无法把它放到一个简单的C#方法,当我输入'255.255.255.192'时,给我'26'# – RoelF 2010-03-24 13:42:59
C#具有位操作运算符。 – wRAR 2010-03-24 14:00:26
我知道。这不是问题。没关系,我明白了。 – RoelF 2010-03-24 14:13:34