When Ziggo change our IP range/subnet, all server already received their new IP address via SLAAC (subnet delegation). Our most important external IPV6 address is our webserver (also needed for LetsEncrypt certificate renewal). When this changes the following updates need to be done on TransIP and our main router/firewall The following steps are required:

1. Get the new IP address that our webserver assigned himself via SLAAC.
2. Update the TransIP AAAA record with the new IP of the webserver
3. On the router update: network/firewall/traffic rules –> Allow-HTTP-ipv6 to new address of webserver
4. On the router update: network/firewall/traffic rules –> Allow-HTTPS-ipv6 to new address of webserver