So after so much fiddling, I think I kinda got my LAN to work. Here's a brief description of topology:
ISP fibre modem connected into RB4011iGS+5HacQ2HnD-IN (let's call this Router).
Router connects to cable on port 10, cable goes through the floor/wall (unfortunately this cable is limiting the connection to 100mbps - I think it might be the keystones), then connects into another RB4011iGS+5HacQ2HnD-IN (let's call this one AP) on port 1 (PoE).
All computers in the house are connected to AP.
So I wanted to make a cabled wireless extension where the AP would also work as a switch.
Router was bought before and was working fine, DHCP leases setup and all. When AP arrived in the mail, I decided to try and use it as an extender.
Long story short, Router is set to Mesh (complaint: Mikrotik's Wiki says):
Never found the so called "Quick guide" for details on HomeMesh.From https://wiki.mikrotik.com/wiki/Manual:Quickset
"Home Mesh: Made for making bigger WiFi networks. Enables the CAPsMAN server in the router, and places the local WiFi interfaces under CAPsMAN control. Just boot other MikroTik WiFi APs with the reset button pressed, and they will join this HomeMesh network (see their Quick guide for details)"
Had to enable CAPsMAN discovery on CAPsMAN itself (used the address as 127.0.0.1, but I know I could've used the port - though I always confuse myself which port, bridge or some ether). Hey Mikrotik, I think we have the first "bug" here.
Tried to enable AP as CAP through Winbox's Quickset. No "automatic connecting" to CAPsMAN.
Turned it on holding reset button. No "automatic connecting" to CAPsMAN.
Turned it on holding reset button until it blinked. No "automatic connecting" to CAPsMAN.
Connected through Winbox, told it to reset config and come back as CAP and it finally worked.
Hey Mikrotik, I think we have a second "bug" here.
Everything seemed to be working kinda fine. Then I decided to copy a huge file (18GB) into my NAS just to check if traffic wasn't unnecessarily passing through the bottleneck cable (since all computers are on the same switch).
And then I noticed it wouldn't finish copying the file. It halts somewhere, Winbox disconnects, and MacOS asks me to eject the network drive, and I don't really know what's going on.
I also noticed my WiFi reconnecting sometimes. Even disconnecting the WiFi and going only with the ethernet, same thing happens. It seems I'm getting random (and extremely frequent) disconnects/reconnects. Even my wife was complaining the internet wasn't working - and she was sitting next to "router", supposedly being served by it's Wi-Fi.
Fixed: plugged in the power supply. It seems an RB4011 doesn't have enough juice to power another RB4011 through PoE.
Only problem now is that 5GHz interfaces are not transmitting.[
They show up as italic in CAPsMAN Scanner window.
Fixed: (kinda; still can't scan) radios were transmitting in a channel my cellphone would not see. I had to manually find and define a few channels/frequencies, and now it transmits. They both transmit on the same channel though, which is kinda bummer, but at least it works.
Hey Mikrotik, I think we have a third "bug" here - CAPsMAN transmits in weird bands - but I recognize this one is relative/not really a bug/too difficult to solve.
Useful info (maybe): 1) I'm running two VMs with virtual ethernet interfaces through a single ethernet cable (one MacOS, one Windows 10). Each one gets their own IP from the router's DHCP. If I disconnect the physical cable, the guest VM doesn't indicate anything. I can try stuff from some baremetal laptop.
2) Upon logging into AP and opening up a terminal to export the config, I noticed some reboot messages. Plugged the power cord and decided to post [this thread] anyway and take some sleep. But out of curiosity: wouldn't it be possible for one RB4011 to power another one through PoE...? It's not even doing something taxing on the resources...
3) I'm kinda tired after spending most of my day trying to get this working, and I need some sleep. If someone has some suggestion on how to start troubleshooting, I'd be really glad!
4) Also downloading files through Winbox result in empty files. Hey Mikrotik, I think we have a fourth "bug" here.
5) Exported with "compact" option.