'Calculating remaining CIDR ranges with Python
I need assistance in calculating in Python the remaining CIDR ranges after i use a subnet.
Example: I want to use a wide range of 10.0.0.0/15 and from it to calculate what available ranges i have left if i substract 10.0.0.0/16 ( the answer should be 10.1.0.0/16 )
But this gets trickier if i want to substract /24 or other actions.
Is there something that can help with this inside Python?
thank you
Solution 1:[1]
This is very easy to do with netaddr module.
from netaddr import *
subnet1= IPSet(IPNetwork("10.0.0.0/15"))
subnet2 = IPSet(IPNetwork("10.0.0.0/16"))
# symmetric difference
result = subnet1 ^ subnet2
print(result)
result: IPSet(['10.1.0.0/16'])
if you want to subtract /24
from netaddr import *
subnet1= IPSet(IPNetwork("10.0.0.0/15"))
subnet2 = IPSet(IPNetwork("10.0.0.0/24"))
# symmetric difference
result = subnet1 ^ subnet2
print(result)
result:
IPSet(['10.0.1.0/24', '10.0.2.0/23', '10.0.4.0/22', '10.0.8.0/21', '10.0.16.0/20', '10.0.32.0/19', '10.0.64.0/18', '10.0.128.0/17', '10.1.0.0/16'])
Solution 2:[2]
Consider your example: you assigned a /16
subnet of your /15
net, so you split your total host address space in two, i.e. the one you assigned, which has a 0
value for the 16th bit, and the one which is still free, and has a 1
for the 16th bit.
Now suppose you had a /14
net. Assigning a /16
subnet would leave you with 3 free /16
subnets, i.e. the ones with respectively 01
, 10
, 11
in positions 15-16. Of course since two of them have 1
in position 15 we may also say you have one /15
subnet (10.2.0.0/15
) and one /16
subnet (`10.1.0.0/16).
And so on.
So when you assign a /24
subnet from your original /15
net you are creating 2**9
(512) /24
subnets: the one you assigned and 511 more. Or you may say you are left with one /16
, one /17
, ..., one /24
free subnet.
I don't know of any libraries for that, but as you see the calculations are simple enough. On the other hand, developing a system to keep track of many subsequent assignments is far from trivial...
If you want a list of all the subnets, this will do:
def ip2int(dec_ip):
t = 0
for e,k in enumerate(reversed(dec_ip)):
t += k*16**(e*2)
return t
def int2ip(int_ip):
ip = []
for e in range(4):
ip.append(int_ip % 256)
int_ip //= 256
return list(reversed(ip))
def subtract_ip(mask, width, sub_width):
subnets = []
int_mask = ip2int(mask)
delta = int(2 ** (sub_width - width))
for d in range(1, delta):
subnets.append(int2ip(int_mask + d*2**(32-width)))
return subnets
subtract_ip([10,0,0,0], 14, 16)
[[10, 0, 1, 0], [10, 0, 2, 0], [10, 0, 3, 0]]
Sources
This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.
Source: Stack Overflow
Solution | Source |
---|---|
Solution 1 | marksoe |
Solution 2 |