Generate Random IP address using PHP

Question

I would like to generate a random IP adress.

Answer 1

On 64-bit PHP:

long2ip(rand(0, 4294967295));

Working in 2021 in any supported PHP version (7.4 and 8.0).

Note: since almost any machine is x64 nowadays and the development of 32-bit operating systems is being abandoned, if this is not working you may probably want to download the x64 version of PHP.

Answer 2

Check the mt_rand func .

You'll probably want to run this :

<?php
    $randIP = mt_rand(0, 255) . "." . mt_rand(0, 255) . "." . mt_rand(0, 255) . "." . mt_rand(0, 255);
?>

Answer 3

$ip = long2ip(mt_rand());

This way is slightly more readable.

Answer 4

According to some answeres here, I decided to add an answere to correct some mistakes that was made...

mt_rand(int $min, int $max);

Some samples used this function with a max values of 4294967295. But this function only supports a max value of 2147483647, whats actually the half. Passing a higher number will return false. Using this function whitout passing anything will also only give the half of the needed value. So

long2ip(mt_rand());

would return a max ip of 127.255.255.255

To have the full range you need some like:

long2ip(mt_rand()+mt_rand());

But even in this sample you will maximum get 255.255.255.254. So to have a full range you need a third mt_rand().

The correct way to get the total range in a short hand code is:

$ip = long2ip(mt_rand()+mt_rand()+mt_rand(0,1));

Beware to use + and not *. Because max value * max value would return 255.255.255.255 as expacted but the chance to get a lower ip isn't that good anymore. To keep good chances using * you could do some like:

$ip = long2ip((mt_rand()*mt_rand(1,2))+mt_rand(0,1));

Answer 5

You could also get a pool of valid IPs from your own webserver logs, if you have any:

cat /var/log/apache2/access_log |cut -d' ' -f1|egrep -v '[a-z]'|sort|uniq > lotsofip.txt

and then in php:

$ips = file('lotsofip.txt');    
echo $ips[array_rand($ips)];