A simple python script converts a Classless Inter-Domain Routing (CIDR)-formatted IP address into an IP range and netmask.

subnet.py

#!/usr/bin/env python
# python subnet.py 200.100.33.65/26

import sys

# Get address string and CIDR string from command line
(addrString, cidrString) = sys.argv[1].split('/')

# Split address into octets and turn CIDR into int
addr = addrString.split('.')
cidr = int(cidrString)

# Initialize the netmask and calculate based on CIDR mask
mask = [0, 0, 0, 0]
for i in range(cidr):
	mask[i/8] = mask[i/8] + (1 << (7 - i % 8))

# Initialize net and binary and netmask with addr to get network
net = []
for i in range(4):
	net.append(int(addr[i]) & mask[i])

# Duplicate net into broad array, gather host bits, and generate broadcast
broad = list(net)
brange = 32 - cidr
for i in range(brange):
	broad[3 - i/8] = broad[3 - i/8] + (1 << (i % 8))

# Print information, mapping integer lists to strings for easy printing
print "Address:   " , addrString
print "Netmask:   " , ".".join(map(str, mask))
print "Network:   " , ".".join(map(str, net))
print "Broadcast: " , ".".join(map(str, broad))

👍
This was really helpful in one of my of scripts. Thanks! :)
👍

very good!

This is awesome! I'm going to suggest that you add line #3:

#!/usr/bin/env python
# python subnet.py 200.100.33.65/26
# from: curl -O https://gist.githubusercontent.com/nboubakr/4344773/raw/subnet.py

That way people can snatch this up and not forget where the got it. I've pointed many people here, because I was able to find the original, because I added that line. But, those people are likely to pass their copy to others directly because they don't have this reference.

You may be interested in some of the additions I've made to your script https://gist.github.com/RichardBronosky/1aed6606b1283277e7ff9eaa18097e78/revisions or the way I am using it to analyze my AWS subnets https://github.com/RichardBronosky/AWS_subnets

Very nice! Ty

mask = [0, 0, 0, 0]
for i in range(cidr):
mask[int(i/8)] = mask[int(i/8)] + (1 << (7 - i % 8))

Sweet. ;)

really nice,
what about if I want to add the first address of the Network to be the gateway?

(addrString,cidrString) = sys.argv[1].split('/')
IndexError: list index out of range

Thanks for that, it have rescue much time for me! :)
But i use Python3 and no Python2 atm, because i have some little errors.
I have just only addet a / to the calculations and addet the new () syntax for the prints.
old:
mask[i/8] = mask[i/8] + (1 << (7 - i % 8))
print "Address: " , addrString
new:
mask[i//8] = mask[i//8] + (1 << (7 - i % 8))
print("Address: " , addrString)

For Python3 users:
`
import sys

(addrString, cidrString) = sys.argv[1].split('/')

addr = addrString.split('.')
cidr = int(cidrString)

mask = [0, 0, 0, 0]
for i in range(cidr):
mask[i//8] = mask[i//8] + (1 << (7 - i % 8))

net = []
for i in range(4):
net.append(int(addr[i]) & mask[i])

broad = list(net)
brange = 32 - cidr
for i in range(brange):
broad[3 - i//8] = broad[3 - i//8] + (1 << (i % 8))

print("Address: " , addrString)
print("Netmask: " , ".".join(map(str, mask)))
print("Network: " , ".".join(map(str, net)))
print("Broadcast: " , ".".join(map(str, broad)))`