Very low throughput on WireGuard via Gluetun Docker (9 MB/s vs 80 MB/s without VPN)

[xxnovosxx 0]

Hello,

I’m having trouble with very low download speeds when using AirVPN (WireGuard) through the Gluetun Docker container, and I’m hoping for some guidance or pointers on what to check next.

### Setup

- Host OS: Linux (Docker host)
- VPN client: qmcgaw/gluetun Docker image
- VPN_TYPE: wireguard
- VPN_SERVICE_PROVIDER: airvpn
- Gluetun is used as a “VPN gateway” container for my download stack.
- Applications:
  - qBittorrent (behind Gluetun)
  - SABnzbd (was also behind Gluetun, now temporarily bypassed for testing)
- Location: Germany
- ISP speed (real, without VPN): ~80 MB/s down on the same machine

In Gluetun I pass the WireGuard parameters from the AirVPN config:

- WIREGUARD_PRIVATE_KEY = <PrivateKey from [Interface]>
- WIREGUARD_PRESHARED_KEY = <PresharedKey from [Peer]>
- WIREGUARD_ADDRESSES = <Address from [Interface], e.g. 10.x.x.x/32>
- WIREGUARD_ENDPOINT_PORT = 1637
- SERVER_HOSTNAMES or SERVER_REGIONS used to select servers (mainly DE/NL)

### What works

The connection itself comes up fine:

- Gluetun logs show:
  - WireGuard setup is complete
  - Public IP address is an AirVPN IP (usually NL/DE)
- DNS is working, healthcheck is green.
- Traffic from containers behind Gluetun does go through the VPN (confirmed by IP checks).

### The actual problem: speed

When my download applications (especially SABnzbd) are routed through Gluetun/AirVPN via WireGuard, I only get about **8–10 MB/s** download speed.

However:

- Without AirVPN / without Gluetun (direct connection), using the same host, same Usenet provider and same test downloads, I get around **80 MB/s**.
- If I take SABnzbd out of the VPN (normal Docker network, SSL directly to my Usenet provider), I’m immediately back at ~80 MB/s.

So the bottleneck appears to be specifically the AirVPN WireGuard tunnel / routing, not my hardware, not Docker, and not my Usenet provider.

### What I have already tried

1. **MTU tuning**

   - I tested path MTU and ended up setting:
     - `WIREGUARD_MTU=1380` in Gluetun.
   - Before MTU tuning I was down in kB/s.
   - After setting MTU to 1380, speeds improved to ~9 MB/s, but that’s still far from the ~80 MB/s I get without VPN.

2. **Different servers / regions**

   - I first used `SERVER_REGIONS=Europe` / `SERVER_COUNTRIES=Germany`.
   - I then switched to **specific servers** with `SERVER_HOSTNAMES=<server>.airvpn.org` (mainly DE/NL servers with low load according to the AirVPN status page).
   - In all cases, the WireGuard tunnel works, but the throughput is stuck around 8–10 MB/s.

3. **Local checks**

   - Host CPU/RAM/IO are fine.
   - No container resource limits that would explain the cap.
   - The same host and same downloads without VPN consistently hit ~80 MB/s.

### What I would like to know

- Is there any **known routing or peering issue** between German ISPs and certain AirVPN DE/NL servers when using WireGuard?
- Are there **recommended optimal settings** (MTU, ports, specific servers or protocols) for high-throughput WireGuard usage with Docker / Gluetun?
- Would you recommend trying **OpenVPN UDP** instead of WireGuard in my situation, and is it expected that WireGuard might perform worse in some routes?
- Are there any additional **debug logs or tests** you would like me to run from my side (e.g. mtr from inside the tunnel to certain locations, specific AirVPN servers to test, etc.)?

I fully understand that there is overhead and that I won’t necessarily get 100% of my line speed through a VPN, but dropping from ~80 MB/s without VPN to ~9 MB/s with AirVPN WireGuard is quite drastic. I’d be very grateful for any suggestions on how to troubleshoot or improve this.

If needed, I can provide:
- anonymized Gluetun logs,
- specific server names I tested,
- and speedtest outputs from inside the VPN tunnel.

Thank you in advance for any help or hints!

Yes i got help from AI english is not my first language

[Staff 10383]

13 hours ago, xxnovosxx said:

After setting MTU to 1380, speeds improved to ~9 MB/s

Hello!

Please set MTU to 1280 bytes and test again. If the problem persists please test from the host, without containers, to determine whether it's a GlueTun specific problem or not. Keep MTU to 1280 bytes and increase at small steps.

Kind regards