Python script to represent a list of CIDR network ranges in the smallest number of CIDR subnets. Subnets can be added and substracted.

cidr_merge.py

#!/usr/bin/env python

import argparse, sys
from netaddr import IPNetwork, IPSet

class IPNetworkArg:
    def __init__(self, network):
        network.strip()
        self.add = True
        if network[0] == '-':
            self.network = IPNetwork(network[1:])
            self.add = False  # I.e remove
        elif network[0] == '+':
            self.network = IPNetwork(network[1:])
        else:
            self.network = IPNetwork(network)
    def __str__(self):
        return ("+" if self.add else "-") + self.network.__str__()
    def __repr__(self):
        return "IPNetworkArg(\"" + self.__str__() + "\")"

parser = argparse.ArgumentParser(
    prefix_chars='/',
    fromfile_prefix_chars='@',
    description='Represent a list of CIDR network ranges in the smallest number of CIDR subnets. The subnets are added to and substracted from the final range in the order they are specified on the command line.'
)
parser.add_argument(
    dest='IPNetwork',
    type=IPNetworkArg,
    nargs='+',
    help='A list of IP Addresses or IP networks in CIDR format (e.g. "192.168.0.0/24"). To substract a range, prefix it with "-" (e.g. "-192.168.0.3"). To load a list from file use "@filename".',
)

if len(sys.argv[1:])==0:
    parser.print_help()
    parser.exit()
vars = parser.parse_args()
ip_network_list=vars.IPNetwork

merged_list=IPSet()
for network in ip_network_list:
    if network.add:
        merged_list.add(network.network)
    else:
        merged_list.remove(network.network)

for cidr in merged_list.iter_cidrs():
    print cidr