Unexpected wireless traffic and CPU usage during ethernet only test

RouterOS Beginner Basics
1

Hi

I recently purchased an hAP ac device to use at home.
So far, I’m using the default configuration of the “Home AP dual” Quickset profile; the only changes I made was to configure a security profile and apply it to both wireless interface.
I have client devices accessing the network from both wireless interfaces and the Ethernet switch.

Every is actually working as expected, but while doing some testing I notice that download throughput from the WAN from the machines connected via Ethernet was far below what it should normally be; when using my ISP provided router, I can normally get a throughput of ~700 Mbps (out of my 1Gbps FTTH link) when running a web based speed test, but when connected via the hAP, I am stuck at ~300Mbps on the very same test.
I poked around using winbox and found out a few things that definitely seems fishy. I initially noticed that when running the speed test, CPU usage topped to 100%, hinting at the fact the router gets CPU bound, but what’s really interesting is that after finding out how to profile CPU usage a bit more finely (I’m completely new to RouterOS…) it appeared that 40% of CPU time during that test is used by the wireless subsystem, despite the fact that all the machines involved are connected via Ethernet
Meanwhile the “interface list” shows the downward traffic from the WAN being transmitted from Eth1 to Eth2 - which is what is expected - but it also shows that traffic being received by both wlan1 and wlan2, despite the fact that no parties involved in the test are connected to it:
winbox_wireless2.png
I then tried to disable both wireless interface and started the test again: this time I managed to achieve the expected 700 Mbps, and while CPU usage reached 100% too, none of that was spent on wireless (thankfully :wink:):
winbox_noWireless.png
Has anyone got an idea about what is going on? As I said, I’m using the OOTB configuration; it this behaviour to be expected?

NB: RouterOS version has been updated to the latest 6.38(stable) and RouterBoard firmware to latest 3.34.

Thanks for your help.

2

Hello again,

As a side note, I wanted to add that this only happens with downward IP traffic coming from the WAN port; no sign of such problem when downloading form another client on the LAN side, or when uploading to the Internet.

This is not exactly crippling for my day to day usage, and I can work around it at the moment by using the hAP as a simple access point with my existing device acting as the router/firewall/eth swtich (with does a pretty decent job at it)
Still, since I’m very far from being an expert but quite keen to learn, I’m burning to know if this behaviour is:

  1. normal (though I seriously doubt it)
  2. Caused by a defect in the firmware
  3. Caused by a misconfiguration on my part (though again, I’m using the OOTB “Home AP dual” config with no changes other than securing wireless accesses)

If anyone got pointers on how I can investigate the issue further, that’d be great!

Cheers!