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))