How to force device to use WiFi AP instead of main router

[BosseSwede]

I am having problems with an IoT device that keeps reconnecting to my main router instead of the nearby AccessPoint.
The IoT sits at a place where the main router's field strength is -96 dBm and I have set up a dedicated AP for it to connect to which provides a field strength of -65 dBm. But it insists of using the far away weak main router's WiFi instead...

It results in the IoT device constantly losing connection and reconnecting using the same weak WiFi.
Both the main router and the AP use the same SSID and I cannot change this because other devices also use the WiFi.

So is there a way to block the IoT device's MAC address from connecting on the main router forcing it to use the AP instead?
Or any other way to not let it use the main router WiFi?

Note that the AP is attached as an extra Access Point to the main router using wired Ethernet and the DHCP server is the main router.

The main router is an ASUS RT-AX86U PRO and the AP is an ASUS RT-AC51U.

I have at present only VPN access to the home network but I can reach the admin pages on both routers through that.

Any advice welcome.

 

[TheLostSwede]

Use a different SSID on the AP or enable the guest network on it and connect the device to it.

 

[bbunge]

Use WIFI MAC filter on the router and deny the client. If it is a dual band client you will have to deny both 2.4 and 5 GHz.

 

[BosseSwede]

Use a different SSID on the AP or enable the guest network on it and connect the device to it.

1. As stated I do not have physical access to the location, everything needs to be done using VPN access.

2. And if I change the SSID on the AP then all devices using that AP will be disconnected...

3. Since I cannot access the troubling IoT device physically it is not possible to change the target SSID in its configuration to the new AP SSID because it stays connected less than a minute each time it connects.

4. If I change SSID on the main router then all of my numerous Raspberries among others will be disconnected.

So the only thing I could think of is to somehow block the IoT device from connecting on the main router, hoping that then it would instead connect to the AP since it uses the same SSID/Password...

 

[BosseSwede]

Use WIFI MAC filter on the router and deny the client. If it is a dual band client you will have to deny both 2.4 and 5 GHz.

That is what I was thinking about when starting this thread but I have no idea if it is possible and if so exactly how one goes about doing it.
Any advice on this much appreciated....

The router is an ASUS RT-AX86U PRO, which was fairly recently installed after a lightning strike killed the LAN adapter on my previous RT-AC86U router.

This happened in the beginning of the summer and before that I never had these problems with the IoT connecting to the weakest WiFi with the same SSID...

 

[Tech9]

Wireless MAC Filter in Wireless settings page, look at the tabs on top. Select the band, enable it, select the device, Apply.

 

[BosseSwede]

I found the place you pointed to but I still do not understand how to use it...
It is very terse as shown in the edited screenshot.

The action can be Accept or Reject. Can the router use both at the same time?
I guess not, right?
So it can be not active (default), reject or accept.
In the latter case it will need a long list of accepted devices I guess....

Last item: If I activate this will it affect ONLY the WiFi on the main router and NOT on the AP?
So when the MAC is allowed in via the AP it will be operational network-wise?

EDIT:
Found this ASUS page on the topic:

[Wireless Router] How to set up Wireless MAC Filter on ASUS Router(WiFi Deny List)? | Official Support | ASUS Global

 

[BosseSwede]

I tried the MAC reject filter on my router and it was accepted for the MAC address of my IoT device.
However after applying the change the device is still connected to the main router's WiFi and is still reconnecting every few minutes as seen by the MQTT log items it sends when connecting.

How can one push the device off the main router's WiFi?

 

[eibgrad]

I tried the MAC reject filter on my router and it was accepted for the MAC address of my IoT device.
However after applying the change the device is still connected to the main router's WiFi and is still reconnecting every few minutes as seen by the MQTT log items it sends when connecting.

How can one push the device off the main router's WiFi?

That was a concern I had about using a MAC filter. The device isn't smart enough to determine that the primary router's wifi is *permanently* inaccessible, so it may just keep retrying. Only now it just never is successful.

Seems to me the better option would be establish a guest network on the AP w/ its own VAP so that particular device has no other option, while not interfering w/ existing devices on the same AP. But AFAIK, AP mode doesn't support guest networks, or any kind of VAPs. That's why I'm not a fan of AP mode w/ ASUS routers; it severely limits your options. Even if you had other options, you being remote isn't helping. That AC51U is mighty old and very limited. I see OpenWRT support, which might provide VAP support. But I'd be inclined to find something much better, like an AC68U for cheap w/ much better options for AP mode (FreshTomato, DD-WRT).

I know that doesn't address your immediate problem, but there may in fact NOT be an immediate solution given all the constraints.

 

[BosseSwede]

OK fair enough...
Have to wait until Sunday when I will be on site again and can power cycle the IoT device hoping it will then forget the connection source and grab the closest.

I have looked at the code for the IoT and it is very rudimentary concerning WiFi connection, it basically only uses SSID + password and once it has connected it seems like the hardware remembers the last connection and tries to re-establish it on resets. That is what I am seeing.

The F/W could be modified such that it will use the AP MAC address when it connects. Then it will be only trying the AP.
But then I need to build a modified d/w and load it to the IoT....

PS, Concerning this forum:
Is there some way to enable the command buttons on top of the edit box so I can more easily do underlines and bold etc?
Right now these are grayed out and I have to enter the actual formatting code manually....
I am using Firefox btw.

 

[ColinTaylor]

PS, Concerning this forum:
Is there some way to enable the command buttons on top of the edit box so I can more easily do underlines and bold etc?
Right now these are grayed out and I have to enter the actual formatting code manually....
I am using Firefox btw.

You have to click on the Toggle BB code icon.

 

[BosseSwede]

You have to click on the Toggle BB code icon.
View attachment 60377

Turns out I had to find and click the 3-dot "More options" icon in order to even see that...
Now working. Thanks.

 

[ColinTaylor]

Turns out I had to find and click the 3-dot "More options" icon in order to even see that...

Ah, right. If your browser window isn't very wide it collapses those options and replaces them with the three dots.

 

[BosseSwede]

Have to wait until Sunday when I will be on site again and can power cycle the IoT device hoping it will then forget the connection source and grab the closest.

UPDATE
I was at home over the week-end and struggled with the connections...
First I tried just to power cycle the device but it connected with the -95dBm low signal nevertheless.
Then I tried to disable the WiFi on the main router with no effect. Strange.
So I brought the IoT device indoors to update the f/w with a new connection SSID and then I changed the SSID of the AP closest to that.

And still problems.

Then I saw that the WiFi antenna on the IoT device looked "strange".
It is a short external WiFi antenna made by stripping off 29 mm on the end of a 120 mm long antenna cable and exposing it as a dipole antenna with the shield pulled back on top of the coax cable towards the connector.
It is supposed to go through a 3 mm hole I drilled in the metal enclosure where the IoT is placed.
At the junction between the inner conductor and the main cable it felt very "weak" and could easily be bent over.
So I decided to make a new such antenna and this time use a shrink tube protection over the last 70 mm of the antenna.
With this in place I tested it indoors inside the roop where the AP is located and got -45 dBm signal strength!
When placed in the final position with the new antenna properly through the hole it still connected fine and got about -74 dBm strength!

So the problem was NOT that it connected to the far away main router at all!
Instead something had damaged the antenna (possibly a bird since the box is embedded in a hedge on the other side of the street and there are a lot of birds around).

If I had a f/w that reports the MAC address of the AP it connects to via MQTT like it does the field strength then this would have been discovered earlier....

Anyway it now seems like it is solid and using the intended AP.