RT-AX68U: Devices falling off network, DHCP OFFER getting lost

[Henfre]

Hi everyone!

I've been chasing this issue for a few weeks, and I feel that I'm so close to solving it. I need some help from the experts here to help me understand my system to see if they can see the reason why this is happening.

Device: RT-AX68U
Firmware: Asuswrt Merlin 386.2_6

Once every three days or so, my devices stop working. They're all still connected, associated, and authenticated with the AP, but I can see from my Wireshark logs that they are sending DHCP REQUEST and there is no answer. On the AP, I have a shell and I'm seeing the requests come in. The server replies with an offer, but the offer isn't actually getting sent out onto the network based on my wireless sniffing. For some unknown reason, my network gets into this condition where devices are unable to observe the DHCP OFFER and thus they lose connection after some time.

Question: Why might the router log the offer going out, but the devices no longer can see it? I have no special configuration; I installed the firmware, factory reset, and configured a fairly basic setup. I'm stumped! I never had this problem with other routers.

 

[ColinTaylor]

As an experiment try removing the guest networks in the first slot and using the second slot instead.

 

[Henfre]

As an experiment try removing the guest networks in the first slot and using the second slot instead.

Thank you so much! I will try that. It takes a couple days after rebooting for the issue to occur, so I'll set a reminder for the experiment five days from today.

What inspires this experiment? I do have a guest network with AP isolation.

 

[ColinTaylor]

What inspires this experiment? I do have a guest network with AP isolation.

The first slots are handled differently from the other two because they're used by AiMesh to propagate guest networks to the nodes. As such they have their own VLANs and bridges. It's an additional layer of complexity at the network level that has caused strange problems in the past. It might not have any bearing on your problem, but moving to slot 2 eliminates it as a possibility.

Run your ifconfig and brctl commands after the change to see how much simpler things are.

 

[Henfre]

Thanks, will do! By the way, it turns out that my wireless driver doesn't support showing wireless unicast, so I might be missing the offers completely. I may have lost my lead on the problem. I'm still going to try running with the change to my guest network.

 

[Henfre]

Conclusion:

My problem is resolved! I'm not sure how, but moving my guest network to the second slot prevents my devices from falling off the network.

Most commonly, my Google home devices were getting disconnected and wouldn't reconnect until a power cycle. This issue seems to be resolved by changing the guest Network slot and making no other changes.

 

[dave14305]

This may or may not explain the reasoning:

Release - Asuswrt-Merlin 386.2_6 is now available

Had to downgrade. Clean install and did 2 full resets and clean setups, but something is wrong with DHCP and manual IP’s being assigned incorrectly.

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