2.4ghz and 5ghz clients cant communicate with each other

[zakovyrya]

FYI, downgrading to Merlin 388.2.2 didn't help, still have the same issue.

 

[Argenti]

I only need access to the 2.4GHz for an old Canon MX430 printer. My new workaround if I cannot access the printer via my laptop :

1) Change from the 5GHz SSID to the 2.4GHz SSID on my laptop.
2) Change back to the 5GHz SSID, I can then access the printer.

I only print a few things a month, so for me this is not really a big deal.

It only happens with the Asus RT-AX86U Pro model. My previous model Asus RT-AX86U had no issues. Both using the latest Merlin firmware. Also checked with a neighbour who is using my old Asus RT-AX82U model (using latest gnuton firmware), he has no issues accessing his 2.4GHz printer, and he has the same setup as me (splitting the 2.4/5 GHz bands to separate SSIDs)

What I experience as well. I have a printer Pi-Star (radio hotspot) that are on 2.4G.

Randomly I wont be able to access either from the 5G network, switch to 2.4 and it works, switch back to 5G and I can access them again, until the fault comes back.

 

[ajawil]

Hi,

Just signed up here as i've been watching but not been subscribed.

I've just changed my router (latest firmware albeit Merlin but has been showing this issue persistently) to match the settings above, and I had to make the following changes from what was there before:

2.4GHz:
Multi-User MIMO: Enable -> Disable
Explicit beamforming: Enable - Dusable
Universal beamforming: Enable -> Disable

5GHz:
Enable Tx Bursting: Disable -> Enable
OFDMA/802.11ax MU-MIMO: DL/UL OFDAM + MU-MIMO -> Disable

Will see how it goes, fingerts crossed! Nice effort doing all the work to get there atkinsom..

Have the issue again. Note I see the issue from a desktop that I've plugged into an old RT-AC68U that I have connected to my AX86U Pro via AImesh...

 

[wsalopek]

I don't know. I can't reproduce on my RT-AX86U. It's Pro models specific issue.

I have this problem on a RT-AC86U - as far as I know, it's a NON pro model - but how can I tell?

 

[Tech9]

You perhaps have completely different issue. This router runs on different firmware, non-Pro model.

 

[mlord]

This issue would explain a problem I have been seeing randomly, where my smartphone sometimes cannot see/control all of the "smart plugs" on the 2.4GHz side. Mmm.

EDIT: Yes, this would explain the irregular behaviour. Switching wifi (both bands) off then on again temporarily "fixes" things, as does a router reboot.

I suspect the issue is when a 2.4GHz device rejoins the network after a pause, or perhaps when it renews. Devices that are present at the point of reboot or off-on work fine initially.

RT-AX68U here.

In my case, the smart plugs (on 2.4GHz) sometimes start blinking to indicate they have lost connectivity.

 

[mlord]

This issue would explain a problem I have been seeing randomly, where my smartphone sometimes cannot see/control all of the "smart plugs" on the 2.4GHz side. Mmm.

EDIT: Yes, this would explain the irregular behaviour. Switching wifi (both bands) off then on again temporarily "fixes" things, as does a router reboot.

I suspect the issue is when a 2.4GHz device rejoins the network after a pause, or perhaps when it renews. Devices that are present at the point of reboot or off-on work fine initially.

RT-AX68U here.

In my case, the smart plugs (on 2.4GHz) sometimes start blinking to indicate they have lost connectivity. So perhaps this instead has something to do with failing DHCP renewals or something on 2.4GHz?

 

[tbrig1]

Has anyone done any packet captures or log review when the issue is present? Have we found how to trigger the bug or force the behavior?

I just had to print again and it was broken again so I thought I’d see if we had a breakthrough here. Disappointed to see so many reports and no fixes.

 

[AlanD]

When the fault happens, there's nothing at all in the logs on my RT-AX86U Pro router.

I also compared the nvram (nvram show > file1.txt), when it was working to when it fails, no relevant differences in there.

I was looking for access point isolation changes, but there is nothing obvious in the logs or nvram.

I've also tried disabling IPV6, the fault still exists.

Another workaround I have found; I have an OpenVPN server setup on the router. With my laptop connecting via an OpenVPN client I can access all 2.4GHz devices with no issues.

 

[mlord]

I guess the thing to capture, would be the iptables configuration when working, and again when not working. It's pretty likely to be in there somewhere, or maybe in the bridging tables.

iptables -L -n -v
brctl showmacs br0

 

[tbrig1]

The tables yes and since router is just running a Linux distro if there are any services that have stopped.

If this is due to memory leak or an exception in code, I don’t know that there’s logging we’d have access to to see an error message but that would be interesting to look at too.

 

[wrtuser]

The same problem for me. I have a mesh (main router RT-AC88U, secondary RT-AC86U, Firmware:386.10).

There are a number of Shelly 2.4Ghz WiFi devices, which are connected to the main and secondary router.

Sometimes, from main wirelessly 5Ghz connected laptop to the main router, a cannot access Shelly 2.4Ghz WiFi devices, which are also connected to the same main router.

But I can access from the same laptop wireless devices which are connected to the secondary router. All devices are always visible from main router or wired-connected hosts!

Today I was able 2 times to reproduce this glitch - when I close the lid of my laptop, after a while open lid again - devices in 2.4Ghz network are not visible.

After a while (random times), all devices are “back” visible.

 

[tbrig1]

Hm, I wonder if it’s the same problem. I can’t disconnect and reconnect or restart a 5ghz client to get the communication working again. Have to reboot the radios or the the whole router to resolve it

 

[AlanD]

The bridging tables from brctl showmacs br0 are pretty much the same before and after the issue.

The iptables from iptables -L -n -v , I'm not too sure what I should be looking for here, but they look very similar.

I've also tried disabling the firewall, this does not fix the issue.

 

[hp1]

I wonder if this is similar to the issue I raised in the 'ASUS RT-AX68U local network WIFI Ping issue' thread. I have a AC86U router and3 AC68U mesh nodes. I have a server that is on 24x7 and can ping all my 2.4Ghz devices all the time (SONOFF S31s with Tasmota and a robot vacuum). From my 5Ghz laptop and wired Windows 11 PCs, it takes anywhere from 10 to 200 ICMP timeouts before the devices become available. I have tried switching to 2.4Ghz on my laptop, but it still takes a while for those devices to respond. I went through a bunch of steps, I turned of QOS, turned of AI Protection (thinking that it might be filtering), but still no success. Accessing these devices in a timely fashion is becoming more and more important, so have to figure out what the issue is. I'm happy to test any suggestions.....

 

[AlanD]

The issue I am seeing is complete isolation of the Wi-Fi 2.4GHz devices and 5GHz devices. No communication (ping/traceroute) whatsoever between these. For devices connected via LAN, there is no issue. The RT-AX8U Pro router can communicate with all devices (2.4 / 5 / LAN) with no issue at all times. When the issue occurs the bridging between the 2.4GHz and 5GHz devices is broken until the router is rebooted.

For myself, sometimes it takes 12 hours, and maximum I have seen is 4 days with no issues.

ASUS support on this issue involves installing stock firmware (they will not support "Merlin") and use the "Feedback" button, and that's all. I sent them a link to this thread, but they are not interested.

If I knew all of this prior to my purchase I would not have "upgraded" from my RT-AX86U router to RT-AX86U Pro router.

 

[mlord]

I get this on my RT-AX86U router. So the upgrade may have nothing to do with it.

 

[AlanD]

I prefer my old RT-AX86U router that never had this issue. Judging by this thread, this issue affects primarily RT-AX86U Pro owners.

 

[glens]

The post prior to yours notwithstanding...

With threads like this it's difficult to remember just what all has transpired. This is affecting the RT-AX86U family only, or does it include others as well?

 

[tbrig1]

Fair enough.

To sum it up, I think what I've seen is that this affects the RT-AX86U, mostly pro versions of the router, either on Asus wrt or Asus merlin. I don't know what firmware version it started in. I personally am coming from an RT-AC1900P that did not exhibit this behavior. After a few days from reboot, 5ghz clients won't be able to talk to 2.4ghz clients and vice versa while using a normal (non-guest network) on the same subnet with AP isolation turned off. 5ghz or 2.4ghz to wired clients works fine.

My router is currently in failed state. I checked iptables (no difference), brctl showmacs (no difference), took a look at the syslog files (I see the firewall daemon has restarted a few times but this apparently is normal. I'm going to setup syslog streaming to my NAS before my next reboot because it looks like syslog logs rotated before I could see anything interesting or maybe log level wasn't set correctly).

Anything else I should try before rebooting it?