TFTP for Cisco Recovery Mode

A Cisco Firepower hardware appliance requires a full reset, including a 1.2 GB boot image downloaded from the vendor portal. The challenge is making this image accessible to a device (e.g., a Cisco FTD appliance) in recovery mode.

The solution? TFTP – a simple, outdated but useful protocol that is suitable for such one-off tasks.

Why Use TFTP Today? ​

Setting up a TFTP server for image or netboot purposes can be frustrating, especially with modern OS limitations (e.g., macOS 12 offering minimal support out of the box).

This guide shows how to quickly perform a firmware restore without unnecessary complications. This process is intended for one-time use — the kind of task you'd hope not to repeat but might come in handy for others facing a similar challenge.

Step-by-Step: Deploying a Temporary TFTP Server ​

1. Prepare the Environment ​

Ensure Python 3 is installed (e.g., via Xcode Command Line Tools) and navigate to a preferred folder (e.g., /tmp/trash-me-soon for a disposable workspace).

2. Set Up a Python Environment ​

Run the following commands to create and activate a virtual environment, then install the tftpy library:

virtualenv venv
source venv/bin/activate
pip install tftpy

3. Create the TFTP Server Script ​

Create a file named server.py with the following content:

import tftpy

server = tftpy.TftpServer('tftp-data')
server.listen('0.0.0.0', 69)

4. Set Up the Data Folder ​

Create a folder to serve or receive data:

mkdir tftp-data

5. Start the TFTP Server ​

Run the script to launch the TFTP server:

python3 server.py

6. Test the TFTP Server ​

Upload a test file to verify functionality:

curl -T test.data tftp://127.0.0.1
# Example: curl -T cisco-ftd-fp1k.6.6.1-91.SPA tftp://127.0.0.1

7. Use the TFTP Server ​

Note the local IP and port (default: 69) to supply when restoring a Cisco FTD appliance. Detailed steps for this process are available in the Cisco reimaging guide.

Conclusion ​

This quick guide demonstrates how to deploy a temporary TFTP server using Python 3 and tftpy to restore a hardware appliance. For recurring tasks, consider setting up a Raspberry Pi 4 as a dedicated FTP/TFTP server. However, for one-off tasks like restoring a Cisco FTD appliance, this method is both efficient and effective.