Local network randomly inaccessible from 5GHz interface

[rochjp]

RT-AX88U, 388.4
Since I installed Merlin 1.5yr ago, I randomly/rarely (6-7x) get this issue: local network simply stops being accessible from a 5GHz connected device, while internet keeps working. Also, this issue never affects 2.4GHz connected devices. Nothing found in the logs. Router reboot fixes it. Any idea what’s going on? Best regards,

 

[MXThaurus]

i think you got a problem with channel, i've seen same problem with Apple devices... try to fix channel and stay under channel 100 (give it a try).

 

[rochjp]

I did notice it on Apple devices and I’m already on fixed channel 36 (no neighbors). But the thing is: internet works flawlessly + I can reach/ping the router. Just not any other local network IP. Similar to what I’d get with the guest network lockdown.

Primary DNS and DHCP is on a Synology on the local network, while the secondary DNS is on the router itself. I usually get a hint of the issue when I have a momentary delay in accessing internet, which I guess is tied to DNS timeouts with the Synology. Or even easier to notice, if the DHCP lease expires.

Not a big issue, it’s a rare occurence. But since I got it this morning, I wondered if it’s fixable.

Update - I just found out something new: Wifi reconnect also fixes it. In this instance, I connected to the 2.4Ghz network for a few minutes, before returning to the 5GHz network. Next time, when the problem returns, I’ll try with another device, to see if it’s indeed connection-related, instead of interface-related.

 

[MXThaurus]

I did notice it on Apple devices and I’m already on fixed channel 36 (no neighbors). But the thing is: internet works flawlessly + I can reach/ping the router. Just not any other local network IP. Similar to what I’d get with the guest network lockdown.

Primary DNS and DHCP is on a Synology on the local network, while the secondary DNS is on the router itself. I usually get a hint of the issue when I have a momentary delay in accessing internet, which I guess is tied to DNS timeouts with the Synology. Or even easier to notice, if the DHCP lease expires.

Not a big issue, it’s a rare occurence. But since I got it this morning, I wondered if it’s fixable.

Update - I just found out something new: Wifi reconnect also fixes it. In this instance, I connected to the 2.4Ghz network for a few minutes, before returning to the 5GHz network. Next time, when the problem returns, I’ll try with another device, to see if it’s indeed connection-related, instead of interface-related.

What router we are talking about? Just to understand, why Synology for DHCP and Primary DNS, can you map your network? In your situation i'll go for sure with a nuclear reset: no backup, no scripts, new configuration, use same SSID and run it for 24 hours and let us know.

 

[rochjp]

Router is mentioned above (RT-AX88U). I won’t be using the nuclear option, since it’s not bothersome enough, with an occurence every 1-2 months. Also, I tend to want to understand the issue; and then fix it.

A few weeks ago, I fixed an unrelated (but similar) issue on my wired network. The culprit: a Sony TV, which would randomly flood the network with pause frames. That’s when I "discovered" that companies can use cheap/unreliable hardware that can cause these sorts of issues.

Thus, my initial assessment: a device floods the 5GHz interface. But even then, it doesn’t make sense if the internet keeps working. Either I’m missing something or misdiagnosing.

I’ll add that I don’t think there’s a bug in the router. Rather, I think that the router, being in the midst of the issue, could help in diagnosing this. But I didn’t find helpful logs. And tcpdump (via USB) is unreliable, too many missed frames.

Any other idea to troubleshoot, when the "event" happens?

 

[MXThaurus]

Router is mentioned above (RT-AX88U). I won’t be using the nuclear option, since it’s not bothersome enough, with an occurence every 1-2 months. Also, I tend to want to understand the issue; and then fix it.

A few weeks ago, I fixed an unrelated (but similar) issue on my wired network. The culprit: a Sony TV, which would randomly flood the network with pause frames. That’s when I "discovered" that companies can use cheap/unreliable hardware that can cause these sorts of issues.

Thus, my initial assessment: a device floods the 5GHz interface. But even then, it doesn’t make sense if the internet keeps working. Either I’m missing something or misdiagnosing.

I’ll add that I don’t think there’s a bug in the router. Rather, I think that the router, being in the midst of the issue, could help in diagnosing this. But I didn’t find helpful logs. And tcpdump (via USB) is unreliable, too many missed frames.

Any other idea to troubleshoot, when the "event" happens?

Let's see if someone has some idea but i think it's hard to find, faster and last solution for me is a 2.4Ghz reboot scheduler once a week and probably your problem will be gone.