Code: (python) [Select]

#!/usr/bin/env python2
def calcSubnet(cidr):
   """
   Calculates the Subnet
   based on the CIDR
   """
   subn = 4294967295 << (32-cidr)   # 4294967295 = all bits set to 1
   subn = subn % 4294967296   # round it back to be 4 bytes
   subn = calcIPNotation(subn)
   return subn



As I work through this more, I think I understand how you found '4294967295 '.  Although 2^32 = 4294967296, is no the same as this; ( (((2^(8*3))*255)+(((2^(8*2))*255)+(((2^(8*1))*255)+(((2^(8*0))*255))))) ) = 4294967295, which is "255.255.255.255" technically the same value.  Still researching as to why that is, but at least that explains what's going on.

Hey there, I've modified your calcSubnet() function to use the proper decimal representation for "all bits set to 1".  I didn't like the use of the number you provided, as I couldn't find a reason (except for, maybe it just worked that way) to use '4294967295'.


Maybe you can provide some insight into why your code was written the way it was?


I feel like mine is still a little sloppy, but I'm still learning quite a lot, so I'm keen to see what you think 




cidr = 16


def calcSubnet(cidr):
        #Cidr into Subnet
        Bits2Zero = 32-cidr             #How many bits we'll need to zero
        Bits2Decimal = 2**Bits2Zero     #The calculation of bits into a decimal
        AllBits = 2**32                 #All bits in a IPv4 Address
        #Convert it
        Subnet = AllBits - Bits2Decimal #Decimal Representation of the subnet address
        Subnet = calcIPNotation(Subnet) #Pass the decimal subnet into the function
        print Subnet                    #Print the subnet adress




calcSubnet(cidr)




And I just made it better



cidr = 29


def calcSubnet(cidr):


        DecimalSubnet = ( (2**32) - (2**(32-cidr)) )
        Subnet = calcIPNotation(DecimalSubnet)
        return Subnet
        InverseSubnet = ~DecimalSubnet
        Inverse = calcIPNotation(InverseSubnet)
        return Inverse


calcSubnet(cidr)