I have zero clue actually, all I know what I see on the router speed test page, are you saying do not worry, would you leave IPv6 enabled?The IPv6 speedtest server may be farther away than the IPv4 server, or the IPv6 server is overloaded. There’s really no way for us to tell you why. A lot can happen between the router and the destination.
Are the results consistent? Are you certain the tests are going to an IPv6 destination?
I have been using the 2.5 port as my WAN port for years and it's rock solid for me. Speed tests are 1230mb on the router which is what my ISP supplies and agrees with the speed test built into my ONT.I would recommend using the default blue WAN port on RT-AX86U and 940Mbps is the maximum throughput for Gigabit Ethernet. In my own experience the green additional 2.5GbE port on external controller is less stable as WAN. No change is needed, IMO.
I have the same router.This specific router model was manufactured with different Broadcom/Realtek 2.5GbE controllers and the user experience may vary.
I have the same router model too. What's inside as hardware may be different though with different drivers running it.
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