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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.
7. Use the following function. it is fast, reliable, and don't use any library. # code to convert netmask ip to cidr number. def netmask_to_cidr(netmask): '''. :param netmask: netmask ip addr (eg: 255.255.255.0) :return: equivalent cidr number to given netmask ip (eg: 24) '''. return sum([bin(int(x)).count('1') for x in netmask.split('.')])
I did find a lot of examples about how to convert CIDR to a network mask, but not the other way around (at least not using PowerShell).
Get the numeric mask by padding the front with 1s and having the cidr make up the rest For each bit, apply the mask Concatenate all the bits together, separated by periods
throw 'ERROR: Invalid Netmask ' + mask. return cidr.split('1').length-1. As the mask is only valid when the bits in 1 go from left to right, the condition checks that no bit is 1 after the first bit in 0. It also checks each group is 0 or 128-255. The method of conversion is mostly the same as the other answers.
To get the CIDR prefix from a dot-decimal netmask like this one: 255.255.192.0 you first have to convert the four octets to binary and then count the most significant bits (i.e. the number of leading ones): 11111111.11111111.11000000.00000000 # 18 ones = /18 in CIDR This function does that rather creatively.
Assuming a well-formed mask (as do all of the other solutions offered here), you can get the CIDR bit count with a single machine instruction. inline uint32_t getBitCountFromIPv4Mask(uint32_t mask) { return __builtin_popcount(mask); // presumes a well-formed mask. } You can do this with IPv6 masks as well.
Considering that a CIDR-notation subnet mask is simply the number of bits that are set to 1, starting at the high end, you can calculate that rather quickly using bit-shift operators and the binary AND operator.
print ip_mask_list. #hardcoded mask for testing. netmask = "255.255.248.0". #convert mask to CIDR. cidr = sum([bin(int(x)).count('1') for x in netmask.split('.')]) print cidr # prints 21. I can convert a mask to CIDR but how would I do it so instead of passing hardcoded netmask variable, I can pass ip_mask_list and it goes thru all masks and ...
Example: I have this netmask: 255.255.255.0 Is there, in bash, a command or a simple script to convert my netmask in notation /24?