2.4ghz and 5ghz clients cant communicate with each other

[tbrig1]

Hi all,
Apologies if this was addressed in another thread, I've been trying the forum search and didn't really find anything applicable.

I have an Asus RT-AX86U Pro running 3004.388.4. I've configured 2 SSIDs a 5ghz one with SSID names formatted like this: WIFI_5G and WIFI. Both SSIDs use the same subnet underneath but I've noticed 5ghz clients cant talk to 2.4ghz clients and vice versa. I'm not sure when this stopped working but I'm pretty sure it worked previously and it definitely worked with this config on an ASUS RT-AC1900P running AsusMerlin.

To give an example of a traffic flow I'm trying to have work - Using a Windows 11, MacOS Ventura client, or iPhone running iOS 17 connecting to the 5ghz SSID trying to send print jobs to an HP Officejet 4650 on the 2.4ghz SSID. This only works if the 5ghz clients move to the 2.4ghz SSID and then icmp and all normal communications (http, print protocols, AirPrint, Bonjour).

AP isolation isn't on and I can't see what about my config would be blocking the traffic, no firewall, no client isolation, etc. I was considering reflashing my router with stock ASUS or Merlin firmware but wanted to see if anyone had any other advice on this first.

Thanks in advance for any input. This has been a great forum to lurk on and typically I can find my answers without even having to post.

 

[L&LD]

Does a simple reboot of the router and the clients solve this issue? Does an electrical reset work?

Electrical reset:

• Unplug the power from the router and the AC wall plug. Leave the power switch on the router 'on'.
• Wait for a minute or two, then power up the router and test.
• Do the same for all devices you're testing with.

Was the router very recently updated to 3004.388.4_0? When was the last time you fully reset the router?

Use the following link to prepare for better troubleshooting tips to follow.

Is it a good idea to keep up with Firmware updates?

I have had issues in the past when updating firmware and Internet speed, But it may have just been a fluke, Should I keep up with the updates? If so On all routers or the nodes as well? What about ones acting as access points? Thanks

www.snbforums.com

Also, ask a mod to move this to the RMerlin subforum since you're running his firmware.

 

[tbrig1]

Thanks for the response. The only thing that seemed to make it work temporarily was toggling on/off AP isolation. Restarting and or unplugging the router made no difference. I upgraded to the 3004.388.4_0 train in Early September but probably noticed it 1-2 weeks ago.

What do you mean by fully reset the router? A reboot? Flash the latest version and reset the config to factory settings?

Thanks, I'll request moving the thread.

 

[drinkingbird]

Thanks for the response. The only thing that seemed to make it work temporarily was toggling on/off AP isolation. Restarting and or unplugging the router made no difference. I upgraded to the 3004.388.4_0 train in Early September but probably noticed it 1-2 weeks ago.

What do you mean by fully reset the router? A reboot? Flash the latest version and reset the config to factory settings?

Thanks, I'll request moving the thread.

Just to be sure, you're talking about the main wireless and not guest right?

Make sure isolation is off on both bands (2.4 and 5). If it seems to keep re-enabling itself, you can try disabling it via the CLI but it sounds like it may be time for a hard reset and manual reconfigure.

 

[tbrig1]

Yup, guest networks are disabled and so is ap isolation.

Would hard reset here be a reflash and factory reset and then a reconfigure?

 

[uildvek]

I just noticed this on my RT-AX86U as well. Clients on 2.4ghz and 5ghz main wifi (not guest) cannot communicate with each other. Client isolation is disabled as well. However in my case a reboot fixed the problem, although I'm on 388.2_2.

 

[tbrig1]

I meant to reply back here. Thanks for the reminder.

I reflashed official ASUS and then reflashed latest Merlin and the issue went away. Didn’t have to change my config or start from scratch. YMMV on that last part.

Also, I did a full power cycle (total power shut off to router) as well. Likely a reflash of Merlin and power cycle was enough but wanted to see if the issue was reproducible on official firmware and it wasn’t.

 

[uildvek]

Welp not 2 hours after rebooting the router the issue came back. I wonder if the issue is caused by iptables rules or something else.

 

[uildvek]

I meant to reply back here. Thanks for the reminder.

I reflashed official ASUS and then reflashed latest Merlin and the issue went away. Didn’t have to change my config or start from scratch. YMMV on that last part.

Also, I did a full power cycle (total power shut off to router) as well. Likely a reflash of Merlin and power cycle was enough but wanted to see if the issue was reproducible on official firmware and it wasn’t.

I'm interested to see if the issue goes away permanently for you after those steps. Hopefully it doesn't come back after a while.

 

[tbrig1]

I completed those steps the day I posted and haven’t had an issue since. Did you set iptables on your own? I don’t see anything set by default in my cli.

Are you using guest vlan’s? Are you using one subnet for the LAN?

 

[Tomik]

Hey, I have the same problem on my AX86U Pro. Restarting only helps for a while

 

[L&LD]

Welcome to the forums @Tomik.

Did you try the steps in the link below?

2.4ghz and 5ghz clients cant communicate with each other

Hi all, Apologies if this was addressed in another thread, I've been trying the forum search and didn't really find anything applicable. I have an Asus RT-AX86U Pro running 3004.388.4. I've configured 2 SSIDs a 5ghz one with SSID names formatted like this: WIFI_5G and WIFI. Both SSIDs use the...

www.snbforums.com

 

[Tomik]

Welcome to the forums @Tomik.

Did you try the steps in the link below?

2.4ghz and 5ghz clients cant communicate with each other

Hi all, Apologies if this was addressed in another thread, I've been trying the forum search and didn't really find anything applicable. I have an Asus RT-AX86U Pro running 3004.388.4. I've configured 2 SSIDs a 5ghz one with SSID names formatted like this: WIFI_5G and WIFI. Both SSIDs use the...

www.snbforums.com

yes, even hard reset.
Now I tested changing the network card driver and it helped.

 

[uildvek]

I still haven't been able to find what's causing it for me. I'm not using VLANs and everything is on the same subnet. Restarting the router fixes it for a day or two and then it breaks again on its own without me having changed anything. I've uninstalled all my addons (I had YazFi and YazDHCP) too and it didn't make a difference. No special iptables rules either. I'm gonna take a snapshot of my iptables rules when it's working and compare it to when it breaks. Are 2.4ghz and 5ghz both on the br0 network interface?

 

[Tomik]

yes, I have both frequencies on br0

 

[tbrig1]

Yup, this broke for me again. No changes to my config. Router uptime is a little over 23 days at this point, can't recall when I needed to print last so can't say exactly when it broke.

 

[uildvek]

Yeah I still haven't been able to figure out what's causing it either. iptables rules are exactly the same before and after breakage. I tried turning off guest networks, firewall, qos, AI protection, and none of them made a difference.

 

[uildvek]

To work around my printer issue at least I was able to hardwire it via ethernet.

 

[tbrig1]

What firmware are you running? I thought I might revert to stock firmware and see if the bug persists.

I can’t find anything in the WiFi 6 standards that would explain the behavior so do we have a bug reporting process for Merlin or stock ASUS?

 

[L&LD]

When running stock firmware, use the feedback button at the bottom of (each?) GUI page.