Validate IP Addresses and Networks with CIDR in Python

First Published: .

Python has a built-in package named ipaddress

You don’t need to install anything to use it.

This simple code shows how to use it

import ipaddress


def check_ip(s_ip_or_net):
    b_valid = True
    try:
        # The IP Addresses are expected to be passed without / even if it's /32 it would fail
        # If it uses / so, the CIDR notation, check it as a Network, even if it's /32
        if "/" in s_ip_or_net:
            o_net = ipaddress.ip_network(s_ip_or_net)
        else:
            o_ip = ipaddress.ip_address(s_ip_or_net)

    except ValueError:
        b_valid = False

    return b_valid


if __name__ == "__main__":
    a_ips = ["127.0.0.2.4",
             "127.0.0.0",
             "192.168.0.0",
             "192.168.0.1",
             "192.168.0.1 ",
             "192.168.0. 1",
             "192.168.0.1/32",
             "192.168.0.1 /32",
             "192.168.0.0/32",
             "192.0.2.0/255.255.255.0",
             "0.0.0.0/31",
             "0.0.0.0/32",
             "0.0.0.0/33",
             "1.2.3.4",
             "1.2.3.4/24",
             "1.2.3.0/24"]

    for s_ip in a_ips:
        b_success = check_ip(s_ip)
        if b_success is True:
            print(f"The IP Address or Network {s_ip} is valid")
        else:
            print(f"The IP Address or Network {s_ip} is not valid")

And the output is like this:

The IP Address or Network 127.0.0.2.4 is not valid
The IP Address or Network 127.0.0.0 is valid
The IP Address or Network 192.168.0.0 is valid
The IP Address or Network 192.168.0.1 is valid
The IP Address or Network 192.168.0.1  is not valid
The IP Address or Network 192.168.0. 1 is not valid
The IP Address or Network 192.168.0.1/32 is valid
The IP Address or Network 192.168.0.1 /32 is not valid
The IP Address or Network 192.168.0.0/32 is valid
The IP Address or Network 192.0.2.0/255.255.255.0 is valid
The IP Address or Network 0.0.0.0/31 is valid
The IP Address or Network 0.0.0.0/32 is valid
The IP Address or Network 0.0.0.0/33 is not valid
The IP Address or Network 1.2.3.4 is valid
The IP Address or Network 1.2.3.4/24 is not valid
The IP Address or Network 1.2.3.0/24 is valid

As you can read in the code comments, ipaddress.ip_address() will not validate an IP Address with the CIDR notation, even if it’s /32.

You should strip the /32 or use ipaddress.ip_network() instead.

As you can see 1.2.3.4/24 is returned as not valid.

You can pass the parameter strict=False and it will be returned as valid.

ipaddress.ip_network(s_ip_or_net, strict=False)
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