Only allow IPv6 addresses in Apache

Question

How would I, in Apache, allow only IPv6 addresses to access my site?

This does not work:

order deny,allow
deny from all
allow from ::/0

It says "The specified network mask is invalid."

Reference:

• https://www.ultratools.com/tools/ipv6CIDRToRangeResult?ipAddress=%3A%3A%2F0

Answer 1

order deny,allow
deny from all
allow from 2000::/3