Bizarrely asymmetric performance of RTL8812AE

Installing and Using OpenWrt
1

I have put together an experimental setup, where OpenWrt 24.10.4 runs in a virtual machine on top of Proxmox with two processor cores and 2 GB or memory given to it. There is a Realtek RTL8812AE wireless card on the host device, passed through to the OpenWrt VM via IOMMU:

root@ProxMoxOW:~# lspci -nn
[Redacted for brevity]
00:10.0 Network controller [0280]: 
        Realtek Semiconductor Co., Ltd. 
        RTL8812AE 802.11ac 
        PCIe Wireless Network Adapter 
        [10ec:8812] (rev 01)
[Redacted for brevity]

The driver information is as follows:

root@ProxMoxOW:~# opkg list-installed *8821*
kmod-rtl8821ae - 6.6.110.6.12.52-r1
rtl8821ae-firmware - 20241110-r2

Speedtest++ run on the VM reports connection speeds of 709.49 Mbps down and 537.01 Mbps up (on a contractually 500 Mbps connection), so the wired subsystem appears to operate adequately. Where it goes off the rails is browser-based tests (speedtest.net, fast.com, etc.) over the wireless connection. Upload speed would be in triple digits, while the download speed would be measured at 3-4 Mbps.

Here’s my wireless configuration (right now, channel is set to 44, but I also tried 36, 40, and 48 with similar results):

root@ProxMoxOW:~# cat /etc/config/wireless

config wifi-device 'radio0'
        option type 'mac80211'
        option path 'pci0000:00/0000:00:10.0'
        option band '5g'
        option channel '44'
        option htmode 'VHT80'
        option country 'US'
        option cell_density '0'
        option disabled '0'

config wifi-iface 'default_radio0'
        option device 'radio0'
        option network 'lan'
        option mode 'ap'
        option ssid 'MyWiFi'
        option encryption 'psk2'
        option key 'VeryVerySecret'

So, what gives and can I fix it? :zany_face:

2

Nothinh bizare, reproduce the problem on bare hardware, 99% it will fail and you go fix proxmox

3

Problem successfully reproduced on bare metal. Download speed still in the 3-4 Mbps range.

4

I ended up replacing the offending Realtek card with an MT7921. That one works as expected. So I am going to close this thread and ascribe the issue to the individual device being faulty.

1 Like
5

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