I do not want to make "clickology" on each device to set "Preffered band" to 5GHz but want to set it somehow in CAPSMAN.
Do you have any idea?

Use a different SSID name.

Thanks but it is obvious solution which needs entering credentials on each device. I am looking for "band-roaming" solution.

This was discussed before. Given similar signal level, most OS will prefer 5GHz. But since 2GHz propagates slightly better inside buildings, you should have better 2GHz signal.

I know that it has been discussed but I do not agree ... most Windows's settings for WiFi is "do not care"/"Any" and IMHO they choose band according to particular driver implementation however I am asking if there is any way to control it manually with CAPSMAN.
I have about 50 computers in mixed 5/2 environment and 80% of them connects to 2.4GHz even the 5GHz's band is comming from same AP. I would like to manually move them from 2.4 to 5 GHz to "free" 2.4 bands.

I have been fighting for a few days with problem of 9 WiFi networks which have apperead from nowhere and polluted my 2.4 bands. There was no method to persude devices to use 5GHz and 2.4GHz signal has been taken as it was stronger but the quality was badly bad.

These rogue AP appeared to be installed in newly bought air conditioners. Imagine .... fresh full power AP installed in each room and interfering with configured network ... if only I could move users in CAPSMAN to 5GHz, there would be no connect/dissconnet to 2.4GHz "disco" during looking for solution.

Correct me if I'm wrong, but what you are looking for is what other people also asked before- band steering. A rather "hackish" thing in its nature, but is reported to work as expected on some other vendor devices. I had an idea of how this can be implemented on Mikrotik AP using RADIUS MAC authentication with some scripting, but, unfortunately, have never been able to find the time to work on this.

Yes. It is what I am thinking of .... but without radius please ... built in CAPSMAN as kind of easy ACL rule.
Do you imagine making scripts for each MAC? Unless you implement MAC list in ROS which despite this particular problem could simplify many other things.

Access lists will allow you to control what device connects to which AP but you have to manually decide.

Perhaps you could do some OUI lookup to determine 5GHZ capable devices or deny access for a while and see if they connect to 5GHz and if not then allow 2GHz ?

It would be a good trick if we could solve this but I haven't had time to look too hard at this.

This was discussed before. Given similar signal level, most OS will prefer 5GHz. But since 2GHz propagates slightly better inside buildings, you should have better 2GHz signal.

As discussed before, many other vendors have implemented band steering functionality and it generally works as expected. Your idea does not. Even Ubiquiti figured it out.

Access lists will allow you to control what device connects to which AP but you have to manually decide.
Perhaps you could do some OUI lookup to determine 5GHZ capable devices or deny access for a while and see if they connect to 5GHz and if not then allow 2GHz ?
It would be a good trick if we could solve this but I haven't had time to look too hard at this.

No, we do not want to do this under any cicumstances. Access Lists are horrible for steering clients (even for dropping them off the WiFi when their signal gets bad).
Looking closer at the probing and association behavior of mobile clients makes it clearer - take the iPhone for example: When it fails to associate to a given AP for a certain number of times (I don't remember the correct number, but it was single-digit), it blacklists the whole SSID, not only the BSSID. That's the point when you have to manually select the WiFi again. And that's what would happen when using access lists.
Android behave a little differently, but not much better at the end of they day.

Steering clients to 5G has to be done on AP/Manager side. Keep a table of mac addresses which are sending probes. if a 2.4 and a 5GHz probe was received from the same MAC address within a certain amount of time (we're talking in the range of millisoconds), only reply with the 5GHz radio, do not answer probes on 2.4 (unless the received signal is too bad on 5GHz but still acceptable on 2.4) Done.

Another approach is adjusting beacon intervals: 102.4ms on 5GHz, 204.8ms on 2.4GHz. Done, but that's still hacky.

Not to mention 802.11v

Unfortunately, MikroTik does not offer any of these. And I get the gut feeling that they don't listen to their users :-(
-Chris

One of working Solutions:
Theory : viewtopic.php?t=178693#p881419

Solution checked in real life 11.2021 rule -120..120 with interfaces 5Ghz - will give piority to 5Ghz

if you have any other rules (mac with comment) - place them before this rules