bill001g :
I would try a firmware upgrade if it exists in case this is a bug.
The only other way I could see this happen is if the 2.4g radio gets better signal and therefore can pass more traffic. If you are using all the bandwidth you buy from your ISP you will see increased ping times. This should be true no matter how you connect to the router but if the 5g radio can not download as fast because of the signal levels it may not be able to use all your bandwidth
As I mentioned I do have newest firmware for my router for around a year now. I also did try reinstalling it.
As for the second part of the quote if that'd be the case then the issue wouldn't appear out of nowhere after years of usage since my router is in the same room as most of my devices (and all I used to confirm the issue) and I do usually use multiple devices at the same time actively (usually laptop on 2.4Ghz and PC but also my phone and tablet, I'm pretty sure i'd notice the ping increase after all those years while downloading apps on google store etc.). Both 2.4Ghz and 5Ghz reach max speeds when tested. Also splitting bandwidth shouldn't cause such drastic increase in ping. (100Mb/s down, 10Mb/s up). When doing simulations speed test on my pc and laptop connected to 2.4Ghz the increase in ping is as described, 57ms during the test, in game ping jumped to 300 while the download speeds more or less halved as expected.
----Edit-----
I may have assumed that 5Ghz causes no problems a bit too early. While during first test it seemingly didn't increase my ping now I do notice an increase (up to 90-100 ms during simultaneous speed test but only around 230 in game which is less than on 2.4Ghz
----Edit2----
I tried to test it between my pc and my laptop and it seems like with more realistic load. (10gb test file at 1.2Mb/s) It Doesn't affect my ping on both 2.4Ghz and 5Ghz.
That said, I did rerun the same tests with my pc and my tablet (Nexus 7 2013 deb with LOS 14.1) while downloading 80mb file on my tablet on 2.4Ghz network and my ping stayed around (in the game) 100-120 which is odd since the exact same file from the exact same source on 2.4Ghz caused my issues before with my ping going up to 300 and prompted me to write this thread. Either I'm losing my mind or the issue is extremely random since my ping was doing that even before I decided to revive my old tablet 2 days ago (it's been happening for around 4 days now, some of the ping spikes that I couldn't connect to me doing something on my devices could be caused by people in other room watching netflix in 4k over wifi or doing something on phones/laptops)
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