Slow LAN Performance Iperf3 RT-AX88u.

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New Around Here
Hi All,

New to this forum, I tried the latest build on my RT-AX88u 386.2.

The update was painless, but I noticed the iPerf3 performance was very low.

I tried Parallel Streams as well as adding a Window Size Parameter, but I wasn't able to go beyond 445Mbps.

Am I missing anything?

Currently am back to Stock Firmware but would love to know if anyone else has done any testing.

Test Setup:

Source: Router Wired.
Destination: Laptop 4 Core/8 Thread

Don't have stats as I fall back to Stock, but 445 is the max it reached.

Thank you.


Senior Member
Just had a go, router as server, windows 10 pc as client, default settings

With Cake (i.e. Runner: Disabled - Flow Cache: Disabled)

iperf3 587 Mbits/s
iperf3 -6 914 Mbits/s

iperf3 -R 947 Mbits/s
iperf3 -R -6 947 Mbits/s

Without Cake (Runner: Enabled - Flow Cache: Enabled)

iperf3 932 Mbits/s (Better)
iperf3 -6 675 Mbits/s (Worse)

iperf3 -R 945 Mbits/s (~same)
iperf3 -R -6 935 Mbits/s (~same)

As for the reasons, no idea!


Asuswrt-Merlin dev
I don`t recommend running iperf3 on the router itself, as the router's CPU will become a bottleneck for iperf itself.

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