[Solution] ASUS AiMesh: Ethernet backhaul still works with firmware mismatch — leave “Ethernet Backhaul Mode” OFF! (Tested on RT-AX86U Pro + RP-AX58)

[muckipup]

Background

Many users (myself included) have struggled with AiMesh instability or node detection failures after upgrading their main router to the 3.0.0.6 (“3006”) firmware branch, while their AiMesh nodes are forced to remain on the older 3.0.0.4 / 388 branch.

Typical scenario:

• Router: RT-AX86U Pro or similar, now on 3.0.0.6.102_34406
• Node: RP-AX58 (or similar extender/router) stuck on 3.0.0.4.388_24694
• Connection: direct Cat 6 Ethernet between router LAN → node WAN

The mismatch between the newer AiMesh 3.0 protocol (in 3.0.0.6) and the legacy AiMesh 2.x/3.0 handshake (in 3.0.0.4) causes pairing problems:

When “Ethernet Backhaul Mode” is ON, the router never discovers the node at all.

ASUS’s UI wording implies this setting must be ON for wired setups, which has led to confusion across Reddit, ZenTalk, and SNBForums. In fact, enabling it with mismatched firmware branches prevents discovery completely.

The test setup

• Router: RT-AX86U Pro (3.0.0.6.102_34406)
• Node: RP-AX58 (3.0.0.4.388_24694)
• Connection: direct Ethernet (no switch)
• Setting: AiMesh → System Settings → Ethernet Backhaul Mode = OFF

Observed behaviour

1. Ethernet Backhaul Mode = ON → node never detected.
   
   The router expects the 3.0.0.6-style discovery signature and rejects the RP-AX58’s older 3.0.0.4 response.
2. Ethernet Backhaul Mode = OFF → node discovered immediately via Wi-Fi.
3. Once joined, AiMesh automatically detects the live Ethernet link and switches the uplink to “Ethernet (1 Gbps)”, even though the toggle remains OFF.
4. The RP-AX58’s Network tab confirms:
   
   • Double green line between router and node on Asus UI demonstrating ethernet connection
   • Uplink Type = Ethernet (1 Gbps)
   • Backhaul Information = Ethernet + router MAC
   • LAN speed test (iperf3) ≈ 930 Mbit/s ↔ true wired throughput.
     
   Confirmed outcome

Even with firmware mismatch:

• Leave Ethernet Backhaul Mode = OFF.
• Allow pairing over Wi-Fi.
• Keep the Ethernet cable connected.
• After joining, AiMesh seamlessly promotes the backhaul to wired.

The “Ethernet Backhaul” toggle controls discovery policy, not live-link enforcement.

Once the link is detected, AiMesh uses it automatically, even across branch versions.

Why this isn’t widely known​

Most forum guidance assumes identical firmware branches, where the toggle behaves as intended.

When branches differ (3.0.0.6 ↔ 3.0.0.4), the newer router’s discovery handshake rejects the older node if “Ethernet only” is forced — which looks like a cabling fault.

In reality, it’s just a protocol mismatch.

This nuance isn’t documented by ASUS and doesn’t appear in release notes, so users end up chasing “bad cables” or “defective nodes” when the fix is simply turning the toggle off.

TL;DR​

For mixed-firmware AiMesh (router 3.0.0.6 + node 3.0.0.4/388):

• Leave Ethernet Backhaul Mode OFF.

• Pair via Wi-Fi.

• The node will auto-switch to Ethernet (1 Gbps) once the link is detected.

• Verified on RT-AX86U Pro (3.0.0.6.102) + RP-AX58 (3.0.0.4.388_24694).

 

[bbunge]

Well, we have been recommending the Ethernet Backhaul Mode be left off for quite a while. Even with matched firmware.
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[jplw]

I had the same problem, but hve always had Ethernet backhaul mode off. Is it possible thast adding a 3.0.0.4 node turns it on? I did not check for that.

 

[drabisan]

I may be using AiMesh for too long, but early days it was documented discovery is only done over Wifi.
I build a setup where the 2 devices couldn't seen eachother over wifi. And ethernet cable in between didn't help at all. I had to bring node close.
Older firmware, agree. But even when I rebuild my own on 3.0.0.6 I only turned on Ethernet Backhaul after adding the node and validating the 10G link is good.

 

[jplw]

When my setup failed to work with my brand new RT-BE58U as router and RT-AX82U as node, I called Asus. They said it should work. They did not tell me or ask me about the backhaul. They said to try swapping router and node. I did. That did not work either. I returned the BE device and have resorted to buying used equipment. Loss of sale for Asus. They should get their act together!

 

[muckipup]

Well, we have been recommending the Ethernet Backhaul Mode be left off for quite a while. Even with matched firmware.
Where have you been?

RT-AX88U Pro mesh node not working after scheduled reboot.

Greetings. So I've seen this issue a few times and thought I should post for help. Network: I have 2 RT-AX88U-Pro routers, one as the main unit, and the other as a mesh node. Backhaul is Ethernet. I have a reboot scheduled every Sunday at 5:02am, just because I like to make sure things are...

www.snbforums.com

Asus RT-AX82u AIMesh Issue

Hi All, Got a bit of a weird issue with my Asus RT-AX82U Router. I wanted to extend the WiFi in the house so purchased an RT-AX52 and set it up as a mesh node. It was a bit far from the RT-AX82U so it's got a 1GB Ethernet connection and I configured that as the backhaul. It appears to be...

www.snbforums.com

Ethernet backhaul failing with unmanaged switch

I'm using a system comprised of a RT-AX86U Pro for my router and several RT-AX86S satellites, all wired for Ethernet. Ethernet backhaul works fine when connecting the satellite WAN port to the AX86U Pro LAN port directly, however when I go through my Netgear GS324 unmanaged switch the...

www.snbforums.com

Not on SNBForums as I only joined recently and wanted to share my personal experience and hopefully add a little to the existing 'knowlegebase'. Sorry if that is a problem.

 

[Untried3868]

Background

Many users (myself included) have struggled with AiMesh instability or node detection failures after upgrading their main router to the 3.0.0.6 (“3006”) firmware branch, while their AiMesh nodes are forced to remain on the older 3.0.0.4 / 388 branch.

Typical scenario:

• Router: RT-AX86U Pro or similar, now on 3.0.0.6.102_34406
• Node: RP-AX58 (or similar extender/router) stuck on 3.0.0.4.388_24694
• Connection: direct Cat 6 Ethernet between router LAN → node WAN

The mismatch between the newer AiMesh 3.0 protocol (in 3.0.0.6) and the legacy AiMesh 2.x/3.0 handshake (in 3.0.0.4) causes pairing problems:



ASUS’s UI wording implies this setting must be ON for wired setups, which has led to confusion across Reddit, ZenTalk, and SNBForums. In fact, enabling it with mismatched firmware branches prevents discovery completely.

The test setup

• Router: RT-AX86U Pro (3.0.0.6.102_34406)
• Node: RP-AX58 (3.0.0.4.388_24694)
• Connection: direct Ethernet (no switch)
• Setting: AiMesh → System Settings → Ethernet Backhaul Mode = OFF

Observed behaviour

1. Ethernet Backhaul Mode = ON → node never detected.
   
   The router expects the 3.0.0.6-style discovery signature and rejects the RP-AX58’s older 3.0.0.4 response.
2. Ethernet Backhaul Mode = OFF → node discovered immediately via Wi-Fi.
3. Once joined, AiMesh automatically detects the live Ethernet link and switches the uplink to “Ethernet (1 Gbps)”, even though the toggle remains OFF.
4. The RP-AX58’s Network tab confirms:
   • Double green line between router and node on Asus UI demonstrating ethernet connection
   • Uplink Type = Ethernet (1 Gbps)
   • Backhaul Information = Ethernet + router MAC
   • LAN speed test (iperf3) ≈ 930 Mbit/s ↔ true wired throughput.
   • Confirmed outcome

Even with firmware mismatch:

• Leave Ethernet Backhaul Mode = OFF.
• Allow pairing over Wi-Fi.
• Keep the Ethernet cable connected.
• After joining, AiMesh seamlessly promotes the backhaul to wired.

The “Ethernet Backhaul” toggle controls discovery policy, not live-link enforcement.

Once the link is detected, AiMesh uses it automatically, even across branch versions.

Why this isn’t widely known​

Most forum guidance assumes identical firmware branches, where the toggle behaves as intended.

When branches differ (3.0.0.6 ↔ 3.0.0.4), the newer router’s discovery handshake rejects the older node if “Ethernet only” is forced — which looks like a cabling fault.

In reality, it’s just a protocol mismatch.

This nuance isn’t documented by ASUS and doesn’t appear in release notes, so users end up chasing “bad cables” or “defective nodes” when the fix is simply turning the toggle off.

TL;DR​

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Interesting. Does this apply across the board, or only with specific models? I ask because I have had no issues with ethernet backhaul mode enabled. Have I just been lucky?

Edit: Is this strictly an Asus firmware issue, or does it apply to Merlin as well?

 

[muckipup]

I was thinking it was a firmware mis-match possibly due to some initial 'handshake" rather than a model mis-match. In fairness, I did not roll-back router firmware to 3.0.0.4 to match the node to test it when a simple toggling off of the ethernet backbone still resulted in the ethernet backbone being formed bizarrely.

 

[bbunge]

Interesting. Does this apply across the board, or only with specific models? I ask because I have had no issues with ethernet backhaul mode enabled. Have I just been lucky?

Edit: Is this strictly an Asus firmware issue, or does it apply to Merlin as well?

You probably have been lucky. Applies to ASUS and Merlin firmwares. If it works for you great. There does not seem to be specifics for Ethernet Backhaul working or not working. Could be hardware or firmware specific. Could be related to the backhaul cabling. Or, could be…who knows?
My Ethernet backhaul works just fine connected to 1 GB ports. When I switch to the 2.5 GB ports it works fine till I change some setting in the router then it goes to WI-FI backhaul. My backhaul is CAT 6 cable and patch cords which should work with 2.5 GB.
Still it is safer to leave the AiMesh settings at default. As is with all things computer, make changes at your peril.

 

[Untried3868]

My Ethernet backhaul works just fine connected to 1 GB ports. When I switch to the 2.5 GB ports it works fine till I change some setting in the router then it goes to WI-FI backhaul. My backhaul is CAT 6 cable and patch cords which should work with 2.5 GB.

I probably should have stated that I too am using the 1GB ports with CAT 6 cables. Thank you for responding.