Slows down entire home network

[skoop321]

qBittorrent & operating system versions

qBittorrent: 4.5.4 x64 Operating System: Windows 11 Pro 21H2 / build 22000.2176 (10.0.22000)

What is the problem?

qBittorrent is slowing down my entire network to the point that all other devices on the network cannot use the internet at all; its as if its using every single kbps of bandwidth on the network. This happens immediately upon starting a download and does not stop until the qBittorrent app is terminated, persisting even after pausing all active torrents. The issue continued even after reducing the download speed to 100kbps and reducing the number of connections to 10 per torrent and 20 maximum. My internet speed is 70Mbps down so bandwidth is not the issue. Using a VPN did not change the result either. I don't think this is due to my router, as I am able to use other torrent clients like Transmission or Deluge with no issues and qBittorrent has worked fine in the past with the same network configuration I have now. I was initially running an older version of the app, but updated to 4.5.4 when I experienced the issue, with no improvement. Attached is the log of my most recent session.

Steps to reproduce

Unknown

Additional context

No response

Log(s) & preferences file(s)

qbittorrent.log

[Seeker2]

Speedtest your internet connection with nothing else going on. You may not have much upload bandwidth and that's where most of the overloads are occurring.

qBitTorrent's settings file might be helpful to spot issues such as 100's of connections at once causing weak networking to become crippled.

[skoop321]

Speedtest your internet connection with nothing else going on. You may not have much upload bandwidth and that's where most of the overloads are occurring.

qBitTorrent's settings file might be helpful to spot issues such as 100's of connections at once causing weak networking to become crippled.

I have a fiber optic connection with 70mbps down and 40mbps upload, so I doubt bandwidth is the issue. As I mentioned in my original post, other torrent clients work perfectly fine with 500 maximum connections, but qBitTorrent takes down my network when using only 20 max.

[Seeker2]

All the more reason to post your qBitTorrent settings or try extremely low advanced settings values for stuff like outgoing connections per second and Max concurrent HTTP announces.

Another thing to try is disabling DHT and Local Peer Discovery under BitTorrent options, these are often especially hard on marginal networking hardware and software.

[krutoivoker]

Test the max bandwidth on a router first with https://iperf.fr

[akgis32]

Its DHT happens to me aswell.

I think its my router that cant handle the connections happens in WIFI aswell in 1Gbit Ethernet. Disable it and try

[cpe-1704-tks]

Is Qbittorrent using networked drives? If so, the local network may be overwhelmed by the I/O velocity,

[Seeker2]

Especially since this occurs: https://github.com/qbittorrent/qBittorrent/issues/14844

[westhouseit]

It's possible this could be mitigated on your network by putting in limiters to handle buffer bloat (https://www.waveform.com/tools/bufferbloat). In any case I'd highly recommend upgrading to a good router that would allow traffic shaping. I grabbed an N100-based miniPC from AliExpress and installed pfSense. Though you can buy the appliances from Netgate to help support development of software firewalls.

Check out Lawrence Systems on Youtube (https://www.youtube.com/@LAWRENCESYSTEMS) for guides, or his forums: https://forums.lawrencesystems.com/

Here's another really good guide series that includes discussion of network concepts: https://www.youtube.com/watch?v=agieD5uiwYY&t=0s