Download speed brutally reduced

Amstellodamois

New Member
Apr 11, 2026
1
0
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Hey all, please be patient: I'm an absolute noob, I don't know what I'm doing :)

Since yesterday, the download speed of my Proxmox VE 8.4.18 node ('cause I still have 900 Mb/s on my other equipments, including on the switch where the node is plugged in) has brutally dropped from 900 Mb/s to...under 10.

This is my Home Assistant History (one of the two VMs of the node) showing it's a fairly recent issue:


1775926864680.png

ping and upload speed (it's capped at only 60 Mb/s, though) are unaffected.

Running a speed test on the other VM confirms the internet bandwidth issue:

1775925306910.png

I didn't test the node itself with a speedtest client but the download speed during an apt install are very bad as well

ethtools looks ok to me:

Code:
root@proxmox:/var/log/apt# ethtool enp1s0
Settings for enp1s0:
        Supported ports: [ TP    MII ]
        Supported link modes:   10baseT/Half 10baseT/Full
                                100baseT/Half 100baseT/Full
                                1000baseT/Full
        Supported pause frame use: Symmetric Receive-only
        Supports auto-negotiation: Yes
        Supported FEC modes: Not reported
        Advertised link modes:  10baseT/Half 10baseT/Full
                                100baseT/Half 100baseT/Full
                                1000baseT/Full
        Advertised pause frame use: Symmetric Receive-only
        Advertised auto-negotiation: Yes
        Advertised FEC modes: Not reported
        Link partner advertised link modes:  10baseT/Half 10baseT/Full
                                             100baseT/Half 100baseT/Full
                                             1000baseT/Full
        Link partner advertised pause frame use: Symmetric Receive-only
        Link partner advertised auto-negotiation: Yes
        Link partner advertised FEC modes: Not reported
        Speed: 1000Mb/s
        Duplex: Full
        Auto-negotiation: on
        master-slave cfg: preferred slave
        master-slave status: slave
        Port: Twisted Pair
        PHYAD: 0
        Transceiver: external
        MDI-X: Unknown
        Supports Wake-on: pumbg
        Wake-on: d
        Link detected: yes

iperf from the node to a VM is excellent:

Code:
root@proxmox:~# iperf3 -c 192.168.0.46
Connecting to host 192.168.0.46, port 5201
[  5] local 192.168.0.42 port 41978 connected to 192.168.0.46 port 5201
[ ID] Interval           Transfer     Bitrate         Retr  Cwnd
[  5]   0.00-1.00   sec  1.94 GBytes  16.6 Gbits/sec    0   1.72 MBytes   
[  5]   1.00-2.00   sec  1.93 GBytes  16.5 Gbits/sec    0   1.72 MBytes   
[  5]   2.00-3.00   sec  1.93 GBytes  16.5 Gbits/sec    0   1.72 MBytes   
[  5]   3.00-4.00   sec  1.91 GBytes  16.4 Gbits/sec    0   2.03 MBytes   
[  5]   4.00-5.00   sec  2.34 GBytes  20.1 Gbits/sec    0   3.09 MBytes   
[  5]   5.00-6.00   sec  2.61 GBytes  22.4 Gbits/sec    0   3.09 MBytes   
[  5]   6.00-7.00   sec  2.48 GBytes  21.3 Gbits/sec    0   3.09 MBytes   
[  5]   7.00-8.00   sec  2.76 GBytes  23.7 Gbits/sec   86   3.09 MBytes   
[  5]   8.00-9.00   sec  2.57 GBytes  22.1 Gbits/sec    0   3.09 MBytes   
[  5]   9.00-10.00  sec  2.26 GBytes  19.4 Gbits/sec    0   3.09 MBytes   
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-10.00  sec  22.7 GBytes  19.5 Gbits/sec   86             sender
[  5]   0.00-10.00  sec  22.7 GBytes  19.5 Gbits/sec                  receiver

iperf Done.

iperf from the node to my desktop (upstairs, using Wifi) is pretty good too (500 Mb/s).


It started yesterday but I don't think (I'm sometimes wary of my memory) I've done anything to the Proxmox. The logs in /var/log/apt/ show some upgrade activity on 2026-03-26 and 2026-04-11 (so, today but not yesterday).

What I've tried: I saw there had been issues between Realtek RTL8111 and r8169 and blindly rushed to install the r8168 that seems to solve the problems for some people. It was a mess: r8168, along with dkms and pve-headers had not installed properly and I rebooted the node in that state. Anyway, I fixed that, my node is back on r8169 and connected but the download problem persists.


What can I do?
(Keep in mind I'm pretty useless)
 
Last edited:
Hi!
check if the nic throws some errors:
Code:
ip -s link show enp1s0
dmesg | grep -E "r8169|enp1s0" | tail -30
You could also try to rule out the cable or switch port:
- Swap the ethernet cable
- Plug into a different switch port
- Check the switch's port stats for errors