Quirks/Oddities you will encounter with Asus RT-AX53U

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? :wink:

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! :+1:
(ASUSWRT only supports VLANs on WAN side).

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Because until you enable such option, your traffic is using the CPU.

:+1: Yes.

Yes. See: https://openwrt.org/releases/snapshot

You can't use DFS channels?

The Power LED isn't properly defined in the dts (?) I don't know what's the proper way to do it but it seems to work properly with my edits.
The USB LED isn't defined in the dts either.
Reading around the forum, the LEDs for MT7915 aren't implemented yet, there's an open issue too in mt76: Please add support for wlan 2,4 and 5 GHz leds on Asus rt-ax-53u #705 following links from there gets confusing.
I'm guessing we need this patch first? [v3] mt76: mt7915: add LED support
LE: we have this: mt76: mt7915: add LED support so something else is missing.
Anyway, for what I could "fix", the Power and USB LED patch (for the current master):

diff --git a/target/linux/ramips/dts/mt7621_asus_rt-ax53u.dts b/target/linux/ramips/dts/mt7621_asus_rt-ax53u.dts
index aec8a0494d..90004b0426 100644
--- a/target/linux/ramips/dts/mt7621_asus_rt-ax53u.dts
+++ b/target/linux/ramips/dts/mt7621_asus_rt-ax53u.dts
@@ -27,10 +27,20 @@
 		compatible = "gpio-leds";
 		led_power: led-0 {
+			label = "blue:power";
 			color = <LED_COLOR_ID_BLUE>;
-                        function = LED_FUNCTION_POWER;
+			function = LED_FUNCTION_POWER;
 			gpios = <&gpio 13 GPIO_ACTIVE_LOW>;
+		usb: led-7 {
+			label = "blue:usb";
+			color = <LED_COLOR_ID_BLUE>;
+			function = LED_FUNCTION_USB;
+			gpios = <&gpio 14 GPIO_ACTIVE_LOW>;
+			trigger-sources = <&ehci_port2>;
+			linux,default-trigger = "usbport";
+		};
 	keys {
diff --git a/target/linux/ramips/image/mt7621.mk b/target/linux/ramips/image/mt7621.mk
index 943fc62ecd..43d95f1e5c 100644
--- a/target/linux/ramips/image/mt7621.mk
+++ b/target/linux/ramips/image/mt7621.mk
@@ -326,7 +326,8 @@ define Device/asus_rt-ax53u
   IMAGE/sysupgrade.bin := sysupgrade-tar | append-metadata
   IMAGE/factory.bin := append-kernel | pad-to $$(KERNEL_SIZE) | append-ubi | \
-  DEVICE_PACKAGES := kmod-mt7915e kmod-usb3 uboot-envtools
+  DEVICE_PACKAGES := kmod-mt7915e kmod-usb3 \
+	uboot-envtools kmod-usb-ledtrig-usbport
 TARGET_DEVICES += asus_rt-ax53u

PS: DFS seems to work properly here.
PS2: kmod-usb-ledtrig-usbport was missing from defconfig.
LE2: v2 patch using the new definitions? used tabs instead of spaces on the power led function line, looks like we need the label too in order for it to work as intended?

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I bought two on black friday too but didn't get them yet.

I'll also use them as dumb APs. The distance between them will be around 7/8 meters and the distance between them and the clients will also be around 7/8m. What do you think about the performance on the range?

Will you burn the second one with openwrt?

Because until you enable such option, your traffic is using the CPU.

I should be more specific...

I was getting high CPU usage after first install of OpenWRT. There was no traffic (other than the laptop I used to login via web browser). ie: It was sitting idle and the CPU load was climbing until approx 1.8 and stayed there (the router itself was getting warm)...This dropped down to 0.06 when I enabled Software flow offloading and Hardware flow offloading (The router then cooled down).

I haven't seen this behaviour before, so I found it a little odd. (I was previously using a TP-LINK C5 AC1200 with OpenWrt as a dumb access point. It didn't display this behaviour.)

You can't use DFS channels?

I should clarify...

On the latest release of the stock firmware (ASUSWRT), the DFS channels are removed from the options.

On OpenWrt, all the DFS channels are available.

For OpenWrt, that is correct. DFS channels are available.
For ASUSWRT, they've blocked out the DFS channels in the options.

I might do some proper testing with benchmark tools...What do you folks use to measure speed?

I've never run speed tests before...I see iperf3 and OpenSpeedTest being demonstrated in Youtube videos.

I'm a total beginner in this situation, so I'll need a few days to learn how to use these tools.

After I do testing, I think I will. This router is a little under-powered with ASUSWRT. But it works well with OpenWrt. Much more responsive! :+1:

Running iperf on a the AP/router as a iperf server and as client on the laptop/mobile is good way to measure the performance.

Was the process to flash openwrt easy?

Ideally you would not run iperf on your networking hardware, it needs to sit in between your client and another device running iperf.


Some testing numbers...

Both RT-AX53U routers (ASUSWRT and OpenWrt) are set as dumb access points.

ThinkPad L520 (LAN) <=> RT-AX53U <=> iPhone XS (WLAN)

iPhone XS wireless capability is...
=> 5 GHz 802.11ac; 2x2 @ 80 MHz = 866 Mbps
=> 2.4 GHz 802.11n; 2x2 @ 20 MHz = 144 Mbps

OpenSpeedTest running on ThinkPad laptop connected to RT-AX53U LAN port at 1 Gbps.
(ThinkPad is running on latest release of Windows 10 Professional).

FIRMWARE: OpenWrt 22.03.2

I ran the test 10 times and averaged the download and upload speeds.

1 metre from router

2.4Ghz = DL: 110.6 Mbps = UP: 107.1 Mbps = Ping: 4
5.0Ghz = DL: 674.1 Mbps = UP: 617.3 Mbps = Ping: 4
2.4Ghz = DL: 84.3 Mbps = UP: 116.0 Mbps = Ping: 5
5.0Ghz = DL: 622.3 Mbps = UP: 610.2 Mbps = Ping: 5

This is North-South orientation...8m from router (2 wooden walls in between)

2.4Ghz = DL: 89.2 Mbps = UP: 97.0 Mbps = Ping: 5
5.0Ghz = DL: 363.0 Mbps = UP: 400.8 Mbps = Ping: 5
2.4Ghz = DL: 73.1 Mbps = UP: 89.9 Mbps = Ping: 5
5.0Ghz = DL: 334.8 Mbps = UP: 388.5 Mbps = Ping: 6

This is East-West orientation...8m from router (3 wooden walls in between)

2.4Ghz = DL: 92.7 Mbps = UP: 89.3 Mbps = Ping: 5
5.0Ghz = DL: 138.8 Mbps = UP: 170.6 Mbps = Ping: 6
2.4Ghz = DL: 67.8 Mbps = UP: 79.9 Mbps = Ping: 5
5.0Ghz = DL: 132.8 Mbps = UP: 141.1 Mbps = Ping: 5

12m from router (4 wooden walls in between)

2.4Ghz = DL: 25.2 Mbps = UP: 11.7 Mbps = Ping: 6
5.0Ghz = NO SIGNAL!
2.4Ghz = DL: 33.8 Mbps = UP: 19.3 Mbps = Ping: 6
5.0Ghz = NO SIGNAL!

I hope this gives people a rough idea on performance with Wifi 5 client.

It was pretty straightforward. Took me less than 10 minutes to do.

What I did was plug the router (LAN 1) into the switch of my network and set a laptop to accept DHCP. Then open up a web browser and typed in router.asus.com ; then follow the guide.

I set it to operate as access point with static IP address, then entered the SSID and Wifi password. After that, I added username and password to the router.

I enabled SSH via Port 22 on the LAN side. => Administration => System => Scroll down to Service section => For Enable SSH , I select LAN only => For SSH Port , I left it as port 22

I install an SSH client (like Putty) on my laptop to login to the router. Type in the LAN IP address of the router and port 22. Login and password credentials are the same as you login into the router via web browser.

Follow the rest of the instructions on the OpenWrt wiki page for RT-AX53U. (You don't need to follow the installation of LUCI part, as the factory image comes with LUCI GUI already.)

Don't rush it or be impatient. Give it time when you write the OpenWrt image to the router. Then run reboot command. If it gets stuck, just power off, wait a few seconds. Then power it back on. After that, OpenWrt should be on there and the default IP address (login via web browser) is ...That's it. Set it up as a dumb access point and you're done.

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I did some iperf3 tests to look at wireless performance...

The setup is...I've already flashed one AX53U to OpenWrt, while leaving the other as stock (updated to the latest ASUSWRT release). I then configured the OpenWrt one as a wireless client and connected to LAN port (to desktop PC). The ASUSWRT one is configured as a dumb access point.

I ran iperf3 with 4 streams for 60 seconds...

Client (OpenWrt) and AP (ASUSWRT)

2.4Ghz AX
=> 248 to 269 Mbit/s
=> 310 to 335 Mbit/s (Reverse Mode)        

5Ghz AX
=> 382 to 442 Mbit/s
=> 501 to 583 Mbit/s (Reverse Mode)

I then flashed the 2nd one to OpenWrt..Then tested again...

Client (OpenWrt) and AP (OpenWrt)

2.4Ghz AX
=> 319 to 348 Mbit/s
=> 366 to 368 Mbit/s (Reverse Mode)

5Ghz AX
=> 377 to 411 Mbit/s
=> 496 to 553 Mbit/s (Reverse Mode)

It looks like the ASUSWRT is slightly faster on 5GHz band, while slower on 2.4GHz.

Out of curiosity, I tested my old AP setup (TP-Link Archer C5) against the new one (RT-AX53U). All using OpenWrt.

Client = RT-AX53U (AX1800)
AP = Archer C5 (AC1200)

1 Stream => 100 Mbit/s
28 Streams => 116 Mbit/s
1 Stream => 253 Mbit/s
28 Streams => 287 Mbit/s


Client = RT-AX53U (AX1800)
AP = RT-AX53U (AX1800)

1 Stream => 198 Mbit/s
28 Streams => 289 Mbit/s
1 Stream => 279 Mbit/s
28 Streams => 430 Mbit/s

I used 28 streams because that is the limit of the Archer C5. The AX53U can handle up to 32 streams. (Each stream is about 14 to 18 Mbit/s).

Another interesting "quirk" I've noticed with the stock ASUSWRT firmware while testing; regarding wireless performance...

Sometimes it suddenly drops speed or stops for a second, but then regains speed moments later. (It looks like some feature in the stock firmware is causing this).

I'm not the only one experiencing this behaviour, this review article indicates the same...
=> https://www.mbreviews.com/asus-rt-ax53u-wifi-6-router-review/
(They have a chart showing their tests for an hour, and there are sudden dips in wireless performance.)

This behaviour does not happen with OpenWrt firmware. The wireless performance remains consistent. No drops in speed when I ran iperf3 for over an hour.

Finally...with the stock firmware, NAT Acceleration is enabled by default. With OpenWrt, be sure to enable Software flow offloading and Hardware flow offloading. (All tests had these enabled by default).

...Think I'll test wired performance next. (NAT, Software/Hardware flow offloading on and off, etc)

Have to correct myself here...It's actually up to 30 streams.

I did lots of testing with iperf3 and used "top" (viewed via SSH) to see CPU usage.

I found an interesting "quirk" of this router in relation to enabling Hardware flow offloading under OpenWrt.

When enabled, this router cannot handle more than 7 simultaneous streams when you use Wifi 2.4GHz band, 5Ghz band, and LAN (cable) all at the same time.

For example:

Wifi 2.4GHz band => 2 streams
Wifi 5Ghz band => 2 streams
LAN (wired) => 3 streams

...Any more will cause the router to drop additional connections.

This does not happen when you just have Software flow offloading enabled or disabled. Under this scenario (simultaneous streams), you can have the following (maximum)...

Wifi 2.4GHz band => 10 streams
Wifi 5Ghz band => 10 streams
LAN (wired) => 10 streams

I noticed this behaviour because I previously tested the LAN side (wired and wireless) individually. So it had no trouble doing 30 parallel streams with Hardware flow offloading enabled...It is when you throw all three (wired and 2.4Ghz/5Ghz wireless LAN connections) into the mix, does this router max out at 7 simultaneous streams.

This could explain why the stock ASUSWRT mysteriously drops to lower speeds, then suddenly jumps back during testing. (NAT acceleration is enabled by default).

So what's the recommendation?

If you're going to use this as a wireless router or dumb access point with OpenWrt, then have:
Software Flow Offloading = ON
Hardware Flow Offloading = OFF

If you're using it this as a pure wired router (1Gb/s connection)
Software Flow Offloading = ON
Hardware Flow Offloading = ON
...The max wired speed is about 910 Mbps down and 850 Mbps up.

With SQM (cake) enabled and Software and Hardware flow offloading disabled; the router maxes out at 200 to 250 Mbps in wired speeds...Which is similar to Edgerouter X. (As they use the same CPU).

Overall conclusion?

If you use this purely as a budget wireless router, its suitable for up to 100 to 200 Mbps Internet plans.

For best performance, use this as a cheap Wifi 6 dumb access point and a low-powered x86-based system for wired routing role. (Suitable for up to 300 to 400 Mbps Internet plans.)

If you want 1Gbit/s wired/wireless performance, this wireless router will not meet your needs. Look at other options.

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? :wink:

hey @stmok

i am getting openwrt working on ax54 (ax54hp , ax1800 S/HP)

ax53u firmwere on ax54hp ( kind of)

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Pls retest with master (so called snapshot version), where this patch landed months ago:

I'm curious whether this patch improves the situation.
Also of note: master has all LEDs working by now thanks to the work of @znevna :slight_smile:

Master comes without LuCI preinstalled, follow instructions 1 and 2 if you require LuCI:

Also of note: master has all LEDs working by now thanks to the work of @znevna :slight_smile:

the wifi 5g/2g led dont work

They should as of two days ago https://github.com/openwrt/openwrt/commit/521efb62ebb55dcc67dc618757aa2e3ccbdf3774

I've tried the following snapshot...

Version: SNAPSHOT (r21968-acd8e94d20)
Date: 2023-02-02 21:01:23

=> LEDs for network ports (LAN and WAN), as well as 2.4Ghz and 5Ghz Wifi are now working!

Upon further testing of SNAPSHOT release...

I've noticed the stock settings for the WIFI 2.4GHz LED is constantly flashing (continuously at regular intervals); even when it's supposed to be idle.

To correct the issue (in LUCI), you need to change the behaviour of that particular LED...

"System" (top menu) => "LED Configuration"
See "WIFI 2.4GHz" and click on "EDIT" button.
Set "Trigger" to "Network device activity" (kernel: netdev)
Set "Device" to Wireless 2.4 Ghz => "phy0-ap0"
Set "Trigger Mode" to enable "Link On", "Transmit", and "Receive"
Click "Save"
Click "Save & Apply"

And now it behaves as it should.

This isn't an issue with "WIFI 5GHz" LED. The network port LEDs (LAN and WAN) behave normally.

Haven't fully tested activity USB LED yet. Just did a quick plug and unplug to see if the LED will come on when plugged into router.

2.4Ghz and 5Ghz Wifi are now working on ax54 too

LEDs for network ports (LAN and WAN) work on ax54 but the way they work is bit funky.