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How to shorten a long IPv6 IP Address to use it in Cloudflare IP lists

Cloudflare WAF Firewall Security Rules are a great way to restrict access to specific URLs / URIs on your website (for instance the admin page (wp-admin) and the rest API path (wp-json/wp/v2)).

I would suggest to limit access to those pages to both your personal IP and your hosting server’s IP.

**Example of a WAF security rule** (excl. admin-ajax which is used for some frontend rules – you can set up a rate limiting rule to limit access to admin-ajax)

In order to prevent being blocked from accessing your own website, you’ll need to add your IPv6 IP address to the list of authorized IPs.

🌐 Example of IPv6 address: 2001:0db8:85a3:0000:0000:8a2e:0370:7334.

The problem is that Cloudflare doesn’t allow the usual long form IPv6 addresses.

This is the error message you’ll get if you try to add a long IPv6 to a list:

Invalid value for ip at position 0: filters.api.IPv6 IP addresses are not supported. We suggest using a /64 CIDR instead (Code: 10038)

In order to register your IPv6, you should convert it to IPv6 CIDR notation.

Vulture provides a tool to easily convert your long IPv6 IP address into a shorter version, compatible with Cloudflare IP list: https://www.vultr.com/resources/subnet-calculator-ipv6/

Simply type in the IPv6 you’ll find via a tool like https://whatismyipaddress.com/ and you’ll get a shortened version you’ll be able to use on Cloudflare. You can also enter the IPv4 format (also for your server).