How to allow an IP (ipv6) address using ufw?
Solution 1:
man ufw is the answer (at line 139), the manual mention this:
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ufw deny proto tcp from 2001:db8::/32 to any port 25
This will deny all traffic from the IPv6 2001:db8::/32 to tcp port 25
on this host. Note that IPv6 must be enabled in /etc/default/ufw for
IPv6 firewalling to work.
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Since the OP not mentioning more detail about his difficulties, I hope this answer may help you to create IPV6 ufw rules