以CIDR格式获取下一个子网

Question

I have the following:-

start_range = "10.40.0.0/16"

end_range = "10.100.0.0/16"

I have to write a logic to iterate over all possible ranges(with same subnet mask /16) from start to end . For each subnet I will be doing some processing and then continuing to the next one.

I could achieve this in trivial way where I know, I have to increment last network octate(ie increment 40 to 41 -> 42 -> 43 and so on).

start_subnet = "10.40.0.0/16"
end_subnet = "10.100.0.0/16"


start_val = int(start_subnet.split(".")[1])
end_val = int(end_subnet.split('.')[1])
subnet_split = start_subnet.split(".")
subnet_split[1] = "{}"
subnet_proto = ".".join(subnet_split)  # "10.{}.0.0/16"

for i in range(start_val, end_val+1):  # iterate from 40 to 100
    cur_subnet = subnet_proto.format(i)   # "10.40.0.0/16", "10.41.0.0/16" etc
    # do processing on cur_subnet

Is there a better(Pythonic) way to get the next subnet(in CIDR format). May be netaddr module has something I am not aware of?

Answer 1

This might be what you have in mind (not really well thought-through or tested, you've been warned!).

The ipaddress module is from python3 but it has a backport, just run

pip install ipaddress

to get it.

import ipaddress


def subnet_range(start_subnet, end_subnet):
    start = ipaddress.ip_network(unicode(start_subnet))
    end = ipaddress.ip_network(unicode(end_subnet))
    assert start.prefixlen == end.prefixlen
    ranges = [
        n
        for ipaddr in ipaddress.summarize_address_range(
            list(start)[0],
            list(end)[0])
        for n in ipaddr.subnets(new_prefix=start.prefixlen)][:-1]
    ranges.append(end)
    return ranges


if __name__ == "__main__":
    start_subnet = "9.250.0.0/16"
    end_subnet = "10.100.0.0/16"


for r in subnet_range(start_subnet, end_subnet):
    print r

Answer 2

Following usage of netaddr helped me to get the expected result.

from netaddr import IPNetwork

start_range = IPNetwork("10.40.0.0/16")
end_range = IPNetwork("10.45.0.0/16")
allowed_range = []

while start_range<=end_range:
    allowed_range.append(start_range)
    start_range = start_range.next()

print allowed_range

This would print the following:-

[IPNetwork('10.40.0.0/16'), IPNetwork('10.41.0.0/16'),
IPNetwork('10.42.0.0/16'), IPNetwork('10.43.0.0/16'),
IPNetwork('10.44.0.0/16'), IPNetwork('10.45.0.0/16')]