Get next IP from a given subnet [Python]

Question

I would like to get the next IP from the given subnet. I know how to get the IP range from notation 192.168.0.1/24 but I do not know how to get the next IP within a range. I wrote this code:

def get_next_ip(ip):
    tmp = ip.split('.')
    val = int(tmp[0]) << 24 + int(tmp[1]) << 16 + int(tmp[2]) << 8 + int(tmp[3])
    val = val + 1
    octet3 = val & 0xFF
    octet2 = (val >> 8) & 0xFF
    octet1 = (val >> 16) & 0xFF
    octet0 = (val >> 24) & 0xFF
    next_ip = str(octet0) + "." + str(octet1) + "." + str(octet2) + "." + str(octet3)
    return next_ip

And when I run print get_next_ip("192.168.0.1") it prints 0.0.0.1 instead of 192.168.0.2 . Why?

Answer 1

It is because of prioritization rules.
The bit shift is not only affecting each tmp[x], but the whole value before the shift operator.
First you shift int(tmp[0]) by 24
Then adds int(tmp[1])
Then shifts the total sum by 16
...

val = (int(tmp[0]) << 24) + (int(tmp[1]) << 16) + (int(tmp[2]) << 8) + int(tmp[3])  

would do it.

Answer 2

Your code does not respect the net mask at all. In fact it does not even use it. You parse for "." and do not care about the "/24".

All you have accomplished is parsing the IP4 Address and then adding 1 to the number ensuring the roll-over is applied.

If you want the next IP in this case the next ip+268

import ipaddress
ipaddress.ip_address('192.168.0.4') + 268
ip_str=str(ipaddress.ip_address('192.168.0.4') + 268

ip_str should now be '192.168.1.16'