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@ldong
Forked from lordkebab/cidr.py
Created April 5, 2018 04:17
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Python script to calculate CIDR values
""" Calculate the subnet mask, its binary representation, number of host and
network bits, and the total number of hosts for a given CIDR address.
Usage: python cidr.py [cidr]
Notes: Pipe the command to jq to pretty print the JSON. Python 2 or 3 compatible.
Examples:
python cidr.py 10.0.0.0/24
python cidr.py 172.0.0.0/16 | jq
"""
from __future__ import print_function
import json
import re
import sys
def netmask(cidr):
# Regex to represent valid CIDR notation
valid_ip = "^(([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.){3}([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])/([0-3]?[0-9])$"
# verify that the user entered a valid CIDR range
if not re.match(valid_ip, cidr):
return json.dumps({'error': 'Invalid IP address'})
net_bits = int(cidr[cidr.find('/')+1:])
num_host_bits = 32 - net_bits
addr_bits = list(('1'*int(net_bits)).zfill(32))
addr_bits.reverse()
host_bits = "".join(addr_bits)
num_hosts = 2**num_host_bits
mask_vals = [128, 64, 32, 16, 8, 4, 2, 1]
# how many full octets do we have
full_octets = int(net_bits/8)
netmask = '255.' * full_octets
remaining_bits = net_bits - (full_octets*8)
if remaining_bits > 0:
mask = sum(mask_vals[:remaining_bits])
netmask = netmask + str(mask) + '.'
netmask = netmask + '0.' * abs((4-(len(netmask.split('.'))-1)))
# chop off the trailing decimal
netmask = netmask[:-1]
# return JSON with all this
d = {'cidr': cidr,
'netmask': netmask,
'netmask_binary': host_bits,
'num_hosts': num_hosts,
'network_bits': net_bits,
'host_bits': num_host_bits,
}
return json.dumps(d)
if __name__ == '__main__':
usage = """
Calculate the subnet mask, its binary representation, number of host and network bits,
and the total number of hosts for a given CIDR address.
Usage: python cidr.py [cidr]
Notes: Pipe the command to jq to pretty print the JSON. Python 2 or 3 compatible.
Examples:
python cidr.py 10.0.0.0/24
python cidr.py 172.0.0.0/16 | jq
"""
try:
input = sys.argv[1]
mask = netmask(input)
print(mask)
except IndexError:
print(usage)
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