MTU Lookup

Script to check network MTU, detect blackhole, and check system PMTUD cache using standard Python libraries. Icecream output is optional.

Required system utilities:

• ping utility
• ip utility on Linux
• netsh utility on Windows

Install

git clone https://github.com/ChieftainGreen/mtu_lookup

Or Copy-paste mtu_lookup.py to a local .py file

For icecream debug output, install icecream:

pip install icecream  # (or pip3...)

And comment out the HAVE_IC = False line

Usage

python3 mtu_probe.py <ip or hostname>  # - Linux
python mtu_probe.py <ip or hostname>    # - Windows

Notes on using system "ping"

PROS

• Available without root/admin privileges
• Available without other Python modules or external programs (e.g., scapy requires Npcap on Windows)

CONS

• Different output for Linux or Windows
• No reliable error code
• Windows version may be localized
• Linux version has no clear 'timeout' message

TODO (Checkboxes)

• Jumbo Frames
• Resolve problem with hostname containing "ttl" substring
• Colored Rich version
• Better no-icecream fallback (no manual commenting)

Author

Igor Perfilov (GitHub). AI also deserves a cookie. 🍪

LICENSE

MIT