About this: I do not observe this behaviour on my sites using PPPoE clients. But use-peer-dns=no must be set on both the pppoe-outX interface, as well as in the DHCPv6 client entry attached to the pppoe-outX interface.
If both those are already turned off, then verify if you have accept-router-advertisements=yes set under /ipv6/settings. Normally if you use PPPoE clients then you should not set that to yes, and should keep the default accept-router-advertisements=yes-if-forwarding-disabled.
Because setting accept-router-advertisements=yes will cause the router to get the DNS information from the RA and put that information in the dynamic-servers list, and there is no option to like use-peer-dns for this part.
Ah, great idea, that this can be overriden with empty.
Gotcha. I apparently missed that totally, that I had this indeed enabled on the dhcp6-client. After disabling peer dns on dhcp6-client, everything works as expected. Many thanks for help.
Both the IPv4 DHCP server as well as DHCPv6 server can dynamically create simple queues for the leases/bindings. These queues are used when you specify limitations (like rate limit). including complex limitations with restrictions from RADIUS.
If the simple queues are only based on the IP address, then if a client device obtains both IPv4 and IPv6 addresses from the router acting as DHCPv4/DHCPv6 servers, you end up with two dynamic simple queues, and the restrictions are applied independently to IPv4 and IPv6 traffic from that client.
If you want to have only one simple queue per client, so that things like rate limiting to 5 Mbit/s can add both the IPv4 and IPv6 traffic, you first have to enable the Allow Dual-Stack Queue setting on both DHCPv4/DHCPv6 server. But then both servers need to have a way to associate both the DHCPv4 lease and the DHCPv6 binding to one single simple queue. The MAC address is a good candidate as identification for DHCPv4 and can be use to identify this queue. But IPv6 use DUID, which means the DHCPv6 server has to be able to somehow extract the MAC address from the DUID of the binding in order to be able to associate it with the simple queue.
It works for DUID-LLT and DUID-LL but for DUID-UUID (which is type 4) obviously the information about the MAC address is not present, hence the error message.
If you have no need for simple queues to apply limitations on the individual clients, or have no need to group IPv4 and IPv6 traffic for those simple queues, them simply disable that "Allow Dual Stack Queue" checkbox in the DHCPv6 server setting and you won't be bothered by the log message anymore.