Fast roaming configuration help

Installing and Using OpenWrt Network and Wireless Configuration
1

Sorry if it has been already asked several times but in the wiki I did not find the information...

NAS ID

Used for two different purposes: RADIUS NAS ID and 802.11r R0KH-ID. Not needed with normal WPA(2)-PSK.

So can i leave it blank if i use the classic WPA2 AES?
Same also for WPA3?

Mobility Domain
I have only one AP, do I have to put the same domain for the 2.4 and 5 network?

Thanks.

2

The documentation is correct, unless you have a strong reason to change those values (as in integrating into an existing/ proprietary installation), you can leave those values unset (then they'll be set automatically with sensible defaults). Technically this applies to WPA2 and WPA3, but WPA3 and IEEE802.11r is pretty much a construction site in terms of client support.

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3

Now everything is clear, thanks!
If i use the same domain for 2.4 and 5 network I get something like band steering?

4

No, for that you'd need to look into DAWN or usteer as well.

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5

OK so in both access points I have to put the same domain, the same for the two bands or is it better to use one domain for 2.4 and one for 5?

6

as far as i understand FT works over same network, i.e. all your member APs should use the same SSID for a mobility domain. which means, as i understand, can be multiple bands but it does not mean you can steer from 2.4 to 5 by using FT (as said before you'll need a steering daemon).

so:

AP1.......................................................AP2
wlan0: 2.4GHz - SSID1 - mobilitydomain1 - SSID1 2.4GHz :wlan0
wlan1: 5GHz - SSID1 - mobilitydomain1 - SSID1 5GHz :wlan1

wlan2: 5GHz - SSID2 - mobilitydomain2 - SSID2 5GHz :wlan2

clients in mobilitydomain1 will roam between the two APs and can use whatever band they want.
clients in mobilitydomain2 will roam independently from mobilitydomain1 clients (only using one band).

this is my understanding. please fix me if needed.

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7

I configured exactly like this, same domain for all bands and APs.

Everything seems to work very well, the devices go from the 2.4 GHz of the AP 1 to the 5 GHz of the second AP without disconnections and the voip calls are perfect.
Basically band steering is managed by clients and fast roaming works fine.

I test everything for a few more days...

8

After many tests I preferred to use two different domains for the 2.4 and 5 GHz bands.

Using a single domain for both bands the connected devices on 5 GHz (AP 1) went to 2.4 (AP 1) very quickly... as soon as I moved away from the AP 1. Then they hook the 2.4 band of the other AP 2 and then, after some time, they connect to the 5 band (AP 2).

Perhaps fast roaming must work precisely in this way ...

I preferred instead that the devices remain connected to one band (5 GHz) switching between APs without disconnections and this is possibile only using one domain for band.

A curiosity about my 5 GHz network ...
AP1 channel 48 and AP2 channel 36 = fast roaming KO
AP1 channel 48 and AP2 channel 100 = fast roaming OK

All the APs are connected with a network cable and on AP2 I had to set the US contry code otherwise it would not transmit on channel 100.

9

Interesting results. So to be clear, with fast roaming enabled you see no call drop, but without it, you see a call drop? And that is interesting about it not working so well from 2.4 to 5 and back.

10

Yes, the phones remain connected to AP 1 and after disconnecting they reconnect to AP 2, it is not possible to make VoIP calls.

I think it is a client problem, they are a bit slow in switching from 2.4 to 5 GHz.

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11

Interesting. Which devices do you have that support it? Do android phones support it? Last I checked it was only my wife's iphone that supported it and my Google pixel did not.

12
  1. are you using auto channel selection? if not can you try with that? try to reduce signal power to eliminate overlap between the 2 APs coverage area.
  2. 2.4GHz is slower but has better coverage than 5GHz.
  3. Fast roaming is not steering, it is a solution to speed up client authentication process.
  4. clients decide which AP or band they want to connect to by default.

If your client prefers stronger signal or 2.4 band in general they will likely to pick and remain on 2.4. To "solve" this we can use band steering to help client to follow our instead of factory preference. There are two typical approaches here (very simplified):

  • give hints to client what are the available APs/bands as some clients if find first AP connects to it regardless if a second AP would be better. it is a kind reminder approach as still clients choose.
  • assuming client can support both bands kick from 2.4 if 5 band is available, i.e force to pick 5GHz band.

your experience will hugely depending on your wifi clients, some (old) devices are not supporting FT, some has bad wifi implementation. E.g my old tablet no matter what I do is very stubborn and not releasing already connected AP only when there is really no signal, even if the 2nd AP is available. My 1year old phone has no problem switching APs when moving around.