Hi,
i would like to know if it is possible to set, for a lan network in Opnsense, an ULA IPv6 Network and an PD (Präfix Delegation) IPv6 Network at the same time and if it is possible how to reach this.
Best reagards
It is possible, yet useless, because ULA IPs have the lowest priority of any adresses, thus the PD GUA IPv6 would always be used as senders. Even IPv4 has higher priority, see RFC 6724. YOu would have to switch any client to disregard that.
If you want to get IPv6 going, see this (https://forum.opnsense.org/index.php?topic=45822.0). Of course, you can do anything you like, but I have tried a lot with IPv6 and that is what works best (for me).
Quote from: meyergru on September 28, 2025, 06:32:57 PMIf you want to get IPv6 going, see this (https://forum.opnsense.org/index.php?topic=45822.0). Of course, you can do anything you like, but I have tried a lot with IPv6 and that is what works best (for me).
Thank you for mentioning this. My Problem is i have a fritzbox infront of my OPnsense and the PD crash after a while. Works in the beginning, but after a while my router decide to delegate new PD so my setup crashes. When i restart my ISC DHCPv6 Lan Client in opnsense i get the PD that works again, but after a while Fritzbox delegate again a new one. So i wanted to try a setup with ULA's so i have stable IPv6 Adresses, without changing the PD setup, which is working when fritzbox won't delegate new PD after a while.
So i try to get as comfortable with opnsense to set this directly to the internet access, but at the moment i'm learning. So i guess for me the best solution is drop PD and use ULA adresses then. I guess a ULA only setup is not the worst option, but the most to configure. Or is there an Option to get the fritzbox to no delegate new PD after a while?
IDK, because I dropped the Fritzbox (https://forum.opnsense.org/index.php?topic=39556) long ago (modulo the telephony and smart home functions). Generally, a router-behind-router scenario is always a hassle, even more so with a limited box like a Fritzbox.
So if anybody facing the same Problem with fritzbox PD (opnsense behind fritzbox), my solution is ULA Adresses. Then you just need to set a static Route in your Fritzbox to the ULA network you definded in OPNsense with the ipv6 gateway of your opnsense wan.
But if there is a solution for a stable PD Delegation from the Fritzbox i would be interested as well (just mentioning that the PD of my ISP is always the same, so this is not the problem here).
If you have a static prefix then do static configuration and route on Fritzbox. No need for PD.