I have a hAP ac3 router connected to a 1Gbit PPPoE connection and a laptop via ethernet. IPv4 works fine and I get around 950Mbit/s on a speedtest however IPv6 only gets around 420Mbit/s on the same speedtest. If I disable all firewall rules in IPv6/Firewall and retest then it gets the full 950Mbit/s the same as IPv4. If I enable one single firewall rule, even something simple like "allow all ICMPv6" then the speed immediately drops down to 420Mbit/s.
I'm assuming that when all rules are disabled the firewall is being disabled and adding a single rule enables it, but why would the speed drop that much. I know there is no fasttrack on IPv6 but it should still be capable of routing over 1Gbit shouldn't it? Somebody else that I know who owns a routerboard does not have the same problem.
I don't have any queues or anything like that configured. Any ideas?