Posted: Sun Aug 30, 2026 1:16 Post subject: RT-AC68U (and others?) recent 5ghz issues and my findings
Including my report I posted within the build thread but I wanted to add to it based on what I've been finding in hopes it could help or maybe get a solution without having to downgrade and still wait.
Mysticales wrote:
Router/Version: Asus RT-AC68U
File/Kernel: asus_rt-ac68u-firmware.trx/Linux Linux 4.4.302-rt232-st78 #15900 SMP Sat Aug 15 03:29:07 +06 2026 armv7l
Previous/Reset: 02/25/2025 - CLI updated, r65908/no
Mode/Status: ap mode/5Ghz issues, Couple IRQ Drops.
Issues/Errors: So everything upgraded fine, so I went to go configure OpenVPN to give it a new shot. Got everything configured, saw it showing as running, that's when I noticed after firewall update later. The 5ghz band won't connect. Tried to systematically go through things like changing wireless security, disabling openvpn thinking maybe it tied itself to something it shouldn't have as Asus can be picky about its tun. At one point I couldn't even connect to 2.4 ghz, but got around that by connecting as a static ip,
Did other steps to try to figure this out but this is where it gets confusing.
If I unbridged the 5ghz, changed the password and have it on a different network range. My device started to connect to it. (Granted no Internet as didn't do any iptable stuff) So either something is with the update and my router and yet another 5ghz story. Or somehow configuring the settings for openvpn and configuring the firewall locked something which makes my 5ghz act either as connection failed or asks for password. (Unless I unbridged) In network I see all three interfaces bridged to br0.
Edit: Chiming in more after seeing previous build posts and how 5ghz is an issue. My take however. While others said they had to be disabled on security to connect. I did manage to connect with wpa2 aes on 5ghz. Just had to be unbridged and a different subnet from the rest. Hopefully this shines a lil more light on it. Anyone know which build works for 5ghz and can keep this openvpn stuff I configured?
So after all this was reading up on of course Linux updates, drivers and normal Asus 68u fun. I saw how what's patching an exploit that could cause the 5ghz to crash by an exploit sending a certain wifi packet and the patch for that is causing the 5ghz to react the same.
Next, my wpa2 aes is still set for the wl1 during this. The ssid is being broadcast and shown locally. Just wont let clients connect or sometimes will ask for the wifi password. (Unless you try what I discovered earlier) Now that in mind. I went to see if it's a driver somehow which to my findings. It does indeed appear that basically the router doesn't know it's there. Router boots up, the physical wireless chip initializes its low-level hardware registers. Part of this baseline chip logic is to automatically broadcast "Beacon Frames" Because the physical radio chip has power and its basic microcode loads, it successfully pumps those beacon frames out into the air showing the 5ghz ssid is out there. (Even with the led not on)
Now I am guessing the software driver crashes during initialization so The Linux kernel never creates the logical network path (wl1) and The data pipeline between the router's brain and the radio chip is completely cut off?
It's like a doorbell on a house that everyone can see but the wires are cut to the actual bell. So when a client attempts to connect to the ssid with security with br0 and the normal interfaces bridged. It just hits a dead end somehow.
But what still gets me curious.. what is allowing the 5ghz to connect when you unbridged that interface and still have security on vs disabled. One would think if it's a driver issue. It wouldn't be so hit and miss?
Anyways not sure if this helps anyone who knows more how to look into things. But just reporting what I learned.
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_________________ ~Battlez-avec la Mystique?~
Asus AC68U/AC1900 (Tmobile) - Firmware: DD-WRT v3.0-r59468 std (02/02/25)
Looking at the signal analyzier screenshot. I'm noticing it thinks my 5ghz mac id is 8C when it's not. It's 7C and the 2.4 is 7A and the main id doesn't end in 8C either.
So could it somehow be that the router shows the mac I'd it's supposed to be but somehow is broadcasting a typo mac id causing all this to happen?
A NVRAM MAC offset corruption bug? Since the addresses do not match up perfectly, the security software flags the authentication request as an illegal/corrupted session and silently drops it?
Gonna try a couple things now with that in mind. Wish me luck. _________________ ~Battlez-avec la Mystique?~
Asus AC68U/AC1900 (Tmobile) - Firmware: DD-WRT v3.0-r59468 std (02/02/25)
One thing to note: Turn off MAC randomization on recent releases. It will flag the client.
I never liked random Mac option to begin with heh. I like having static IPs set within my router so I know which ip goes where and at a glance if I see something not labeled or diff. I can spot it faster. Luckily to this day never had anyone random on my lan but never hurts to keep eyes open or to see if any device is opening connections more then it should. (Google home. I'm looking at you) _________________ ~Battlez-avec la Mystique?~
Asus AC68U/AC1900 (Tmobile) - Firmware: DD-WRT v3.0-r59468 std (02/02/25)
Might be something with how these models handle virtual interfaces? I've been speculating it could be something where the router panics and starts shutting down before it thinks it will crash. Would explain irq stuff I've seen. _________________ ~Battlez-avec la Mystique?~
Asus AC68U/AC1900 (Tmobile) - Firmware: DD-WRT v3.0-r59468 std (02/02/25)
Upgraded to 8/31 build and still not able to connect to 5ghz w1
However.. oddly if I make a virtual ssid for the 5ghz. W1.1, add normal wpa2/aes security. Devices can connect to that just fine. _________________ ~Battlez-avec la Mystique?~
Asus AC68U/AC1900 (Tmobile) - Firmware: DD-WRT v3.0-r59468 std (02/02/25)
Check to ensure that your SSID and password have all valid characters.
Gave that a shot to rename the ssid and security password to something else fully. No luck. Still won't connect to the w1
Which makes me wonder how is it connecting to the w1.1 on 5ghz but not as the eth2 (w1)? _________________ ~Battlez-avec la Mystique?~
Asus AC68U/AC1900 (Tmobile) - Firmware: DD-WRT v3.0-r59468 std (02/02/25)
Just did a fresh flash and nvram reset (followed by easyddup to save time on settings and sadly it doesn't do everything)
But before I reapplied settings. Tested 5ghz. Indeed. With security disabled. Connects. Moment I add security it doesn't. In fact it acts like password is wrong many times.
Attached is my phones wifi diag during the attempts. Where it seems client sends the 4-hand auth pass but router drops it moment it does and then thinks something else.
Been wondering if it's possible things are going too much on a single core and causing irq 27 and 29 to act up. Think 27 was the master clock of the router?
Either way. Something is messing with the handshake. :/
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_________________ ~Battlez-avec la Mystique?~
Asus AC68U/AC1900 (Tmobile) - Firmware: DD-WRT v3.0-r59468 std (02/02/25)
...so are we having issues with the radio turning off across multiple models of broadcom-based routers? Asus, R7000, netgear ex6200 ...or am I reading this all wrong.
Joined: 16 Mar 2019 Posts: 452 Location: Szczecin, Poland EU
Posted: Sat Oct 03, 2026 18:17 Post subject:
Last good build with 5GHz wifi working correct is from May 8, 2026. Any newer version have problem with connect devices to 5GHz AP. When network is configured as open everything is ok. When we have secured AP we can't use 5GHz wireless network. It's not problem with random MAC. Currently I have advanced wifi configuration made follow DD-WRT wiki tutorial and it not solve problems.
Unless you make a virtual ssid for the 5ghz which THAT one you could have security on and it would work. Not ideal tho since the.
As for Nas and Linux.c and all. One time my study of it was showing if maybe I seperated what runs on what core. As what happened during the startup is two of the IRQs had to panic out which I believe one of those would be so ething that handled the part that gets the 5ghz going. So the analogy was the Doorbell is installed, is ready to be pushed. But inside. It's not connected to the chime/bell.
I need to upgrade to may still.. can't be out there without the patches against internet exploits going on. _________________ ~Battlez-avec la Mystique?~
Asus AC68U/AC1900 (Tmobile) - Firmware: DD-WRT v3.0-r59468 std (02/02/25)
