wg-mtu-auto

Automatically detect the optimal WireGuard MTU by analyzing your local egress interface and optionally probing the Path MTU (PMTU) to one or more remote hosts.
The tool ensures stable and efficient VPN connections by preventing fragmentation and latency caused by mismatched MTU settings.

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✨ Features

• Automatic Egress Detection — Finds your primary internet interface automatically.
• WireGuard MTU Calculation — Computes wg0 MTU based on egress MTU minus overhead (default 80 bytes).
• Optional Path MTU Probing — Uses ICMP “Don’t Fragment” (ping -M do) to find the real usable MTU across network paths.
• Multi-Target PMTU Support — Test multiple remote hosts and choose an effective value via policy (min, median, max).
• Dry-Run Mode — Simulate changes without applying them.
• Safe for Automation — Integrates well with WireGuard systemd services or Ansible setups.

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🚀 Installation

Option 1 — Using pkgmgr

If you use Kevin Veen-Birkenbach’s package manager (pkgmgr):

pkgmgr install automtu

This will automatically fetch and install wg-mtu-auto system-wide.

Option 2 — Run directly from source

Clone this repository and execute the script manually:

git clone https://github.com/kevinveenbirkenbach/wg-mtu-auto.git
cd wg-mtu-auto
sudo python3 main.py --help

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🧩 Usage Examples

Basic detection (no PMTU)

sudo automtu

Specify egress interface and force MTU

sudo automtu --egress-if eth0 --force-egress-mtu 1452

Probe multiple PMTU targets (safe policy: min)

sudo automtu --pmtu-target 46.4.224.77 --pmtu-target 2a01:4f8:2201:4695::2

Choose median or max policy

sudo automtu --pmtu-target 46.4.224.77,1.1.1.1 --pmtu-policy median
sudo automtu --pmtu-target 46.4.224.77,1.1.1.1 --pmtu-policy max

Dry-run (no system changes)

automtu --dry-run

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🧪 Development

Run unit tests using:

make test

To see installation guidance (does not install anything):

make install

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👤 Author

Kevin Veen-Birkenbach https://www.veen.world