To verify that IPv6 is working on your Server, make a ping test to Google:

ping -6 google.com

If you see the following output, then IPv6 is working.

root@demo-cloud:~# ping -6 google.com
PING google.com(fra07s29-in-x200e.1e100.net (2a00:1450:4001:802::200e)) 56 data bytes
64 bytes from fra07s29-in-x200e.1e100.net (2a00:1450:4001:802::200e): icmp_seq=1 ttl=116 time=6.69 ms
64 bytes from fra07s29-in-x200e.1e100.net (2a00:1450:4001:802::200e): icmp_seq=2 ttl=116 time=5.19 ms
64 bytes from fra07s29-in-x200e.1e100.net (2a00:1450:4001:802::200e): icmp_seq=3 ttl=116 time=5.20 ms
64 bytes from fra07s29-in-x200e.1e100.net (2a00:1450:4001:802::200e): icmp_seq=4 ttl=116 time=5.25 ms
64 bytes from fra07s29-in-x200e.1e100.net (2a00:1450:4001:802::200e): icmp_seq=5 ttl=116 time=5.24 ms
^C
--- google.com ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 4004ms
rtt min/avg/max/mdev = 5.191/5.512/6.685/0.586 ms
root@demo-cloud:~# 

However, if you see the output below, then IPv6 is not working. In this case, please contact your Server/Hosting Provider for assistance with IPv6 configuration.

root@demo-cloud:~# ping -6 google.com
ping: connect: Network is unreachable

[Example] IPv6 configuration instructions on a Hetzner Dedicated Server (using Debian / Ubuntu 22.04+)

If IPv6 config is not yet present in /etc/network/interfaces, update the following:

iface <INTERFACE_NAME> inet6 static
  address <IPv6 Subnet Prefix>::2
  netmask 64
  gateway fe80::1

Replace <INTERFACE_NAME> and <IPv6 Subnet Prefix> with your real Interface Name and IPv6 Prefix, respectively.

After configuration, restart the Networking service or do a full server reboot.

root@demo-cloud:~# service networking restart

For further guidance, please review Hetzner's related documentation.