As per his post, by going through below link, it will provide Network CIDR
Here we can check the another method to find the Network CIDR
STEP 1 : Go to the below website to get the IP – http://flashwebhost.com/ip.php
STEP 2 : Open Terminal and add your IP like below
STEP 3 : The above command will provide the first and last IP.
10.0.0.0 - 10.0.0.255
STEP 4 : Go to https://www.ipaddressguide.com/cidr and enter first and last IP and then click calculate button
I used the Network CIDR to secure wordpress using .htacess