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I have just got the Gigafast Pro service installed and the ethernet speeds are good, as expected however the WIFI performance of the router is pretty poor.
Even when standing directly next to the router connected over 5Ghz Wifi AC, 80Mhz bandwidth, actual link speed is showing as 700-850Mbps my download / upload speed maxes out at 200-250Mbps.
Speedtest from ethernet port:
Wifi connection stats:
5ghz AC Wifi supports up to 1300Mbps and as you can see my actual link speed is showing as 780Mbps so why am I only getting 230Mbps down?
Take a look at these threads and see if anything there helps.
Suffering the exact same issue as you, similarly a number of other users are also facing this problem.
There has been no fix or acknowledgement from Vodafone that there is actually an issue except asking customers to use their Wifi 'xperts' (I will reserve judgement on commenting on that title).
Haven't been able yet to test an alternative router to check if the Wifi speeds are the same.
It appears at present that Vodafone have some sort of restriction/limiting factor causing us all to max out Wifi around 200-240mbs (unintentional or intentional?).
So I suspect that the reason for the subpar WiFi performance with the provided Vodafone router is that the hardware sucks. There are no external antennas at all.
I have replaced the provided Vodafone router with an Asus RT-AC86U and now my WiFi performance is pretty much doubled. I should really have gone for a WiFi 6 AX router which I kind of regret now but for the time being this will suffice.
Just to add I did ring the 'Wifi Xperts' and whilst I was pleased it was UK based staff they basically said they could see no errors on the wifi and that they only guarantee up to 10Mbps on wifi lol!
If you've only just brought your Asus RT-AC86u - as a previous user of one, I'd get a cooling fan kit for it. Nice little router, but it will slowly cook itself if you don't add active cooling!