I recently bought two RT-AX53U routers from a Black Friday sale. (Half the regular price). I decided to install OpenWrt on one. For the other one, I updated to the latest ASUSWRT release to compare against OpenWrt.
Here's interesting things/oddities you may encounter after installing OpenWrt...
(1) High CPU usage after you first install OpenWrt...
I've noticed upon first login (no password set) on OpenWrt, the CPU load is constantly high until I enable Software flow offloading and Hardware flow offloading in "Network" => "Firewall". Load average drops from 1.78 to 0.06 ...I have no idea why it behaves this way. Anyone else encounter this?
Bare in mind, I've noticed the stock firmware is spectacularly sluggish compared to OpenWrt. It boots up a lot longer and you have to wait a bit for the screen to load up when managing the device through a web browser. It is rather warm to touch on the bottom of the router.
(2) The power LED isn't on by default with OpenWrt...
This can be corrected by selecting "System" => "LED Configuration"
=> Click Add LED action button
=> A window will pop up, just fill in as follows...
Name: Power LED
LED Name: blue:power
Trigger: Always on (kernel: default-on)
=> Click Save and then Save & Apply
(3) Wifi LEDs don't yet work.
=> As already discussed in this thread: ASUS RT-AX53U wireless LEDs do not light up
...Only the LAN, WAN, and Power LEDs work. I didn't test the USB LED.
(4) While installation was trouble-free (for me at least)...
There is no need to install LUCI as mentioned in the OpenWrt instructions for the RT-AX53U.
=> https://openwrt.org/toh/asus/rt-ax53u
That only applies to snapshot releases. OpenWrt 22.03.2 factory release already has LUCI by default. So skip the mentioned LUCI install step and reboot it.
I'm running this OpenWrt/RT-AX53U setup as a dumb wireless access point, so there maybe other things I have yet to encounter. (I don't use the USB connector).
(5) What about performance?
The stock firmware performs better in wireless because its using closed-source blobs. It also looks like (the one I have) is set to the Asian region for wireless country code (I can't change it to anything else). So it could be cranked up in power. Where as in OpenWrt, I've set it to Australia in country code.
There is a notable difference in wireless range, but not huge. (Only really affects outside the house, the OpenWrt install covers indoors perfectly for my small home).
OpenWrt boots faster (less than a minute) and using the interface (through web browser) is much more responsive.
It takes quite a while for this router to start up with the stock ASUSWRT firmware (even on the latest release). I don't know what ASUS did to their version of WRT, but its sluggish on this router.
I've set both to be Access Points, so there is no special ASUS features enabled like anti-virus or bandwidth control. The stock one runs warm, while the OpenWrt install is notably lower in temperature (cooler to touch compared to stock one).
(6) Other things that is not OpenWrt related, but could be of note...
An ASUS representative in Australia said some interesting things about this router.
It does not support...
=> 160 MHz bandwidth (5GHz band)
=> DFS channels
=> ASUS "Smart Connect" (Combines both wireless bands into one SSID, and determines/assigns which is the best band to use for connecting a wireless client). They recommend you to manually run the 2.4GHz and 5Ghz bands separately with two different SSIDs.
In Australia, there's another model called RT-AX54HP (It's called something else in other regions). In terms of specifications, it is very similar to the RT-AX53U, except it does not have the USB connector and has 4 LAN connections instead of 3 LAN. (Looking through the ASUS GPL source code for that model, it seems to be based on the same Mediatek hardware as RT-AX53U)...Maybe a future addition to the OpenWrt table of hardware?
Anyway, I hope this gives people a rough idea of what to expect, if they want to purchase this router for OpenWrt. It's really a budget solution, but works well if you don't use the stock firmware.
Besides, OpenWrt supports VLANs on the LAN side! ...And I need that capability!
(ASUSWRT only supports VLANs on WAN side).