How to define an API key to work only within a specific IP range in five easy steps

In the example below we will use https://www.whatismyip.com/ to get our IP address.
We will use https://www.ipaddressguide.com/cidr to convert the desired IP range to format CIDR (Classless Inter-Domain Routing).

ONE
Our IP address is 212.205.179.166

The CIDR format for range 212.205.179.166 – 212.205.179.167 (which includes our IP address) is 212.205.179.166/31

TWO

When creating a new API key or editing an existing API key we will add 212.205.179.166/31 for the IP range

THREE

We will test this IP from the computer with IP address 212.205.179.166 by doing a GET on a bibliographic record.  It works.

FOUR 

Now in the IP range of the same API key we will put 212.205.179.168/31 which is the CIDR format for IP range 212.205.179.166 – 212.205.179.167 (which does not include our IP address) 

FIVE

Now the API does not work and gives message “HTTP requests from IP address 212.205.179.166 are not allowed”