Quick TFTP Recovery Setup

Sometimes you need to recover a bricked device via TFTP, but you probably don’t have a TFTP server available. So here’s how to quickly set one on your local PC.

I recently had to recover a broken GXP1625 IP-Phone, but the recovery guide assumed a Windows installation. Here’s how to quickly replicate that setup on linux, without having to make any permanent changes to your system.

Disable Firewall

Let’s disable the firewall for now so that it does not interfere:

sudo systemctl stop firewalld

Run DHCP Server

Open your network configuration UI and assign the static IP address 192.168.7.1 to the network interface you want to use for debugging. If your bricked device supports recovering from a specific static address (usually home network routers), use that one of course.

Now let’s run a DHCP server:

# dnsmasq is usually installed. If not, use podman like for the tftp server
sudo dnsmasq --interface=enp1s0 --port 0 --no-daemon --dhcp-range=192.168.7.50,192.168.7.100,12h --dhcp-option=66,192.168.7.1

In this command, we disable the DNS server (--port 0), start a DHCP server on interface enp1s0. We also set DHCP option 66 to tell our IP-Phone there’s a TFTP server for provisioning at 192.168.7.1.

sudo pkill dnsmasq

Run TFTP Server

To finally run the TFTP server:

sudo podman run --rm --net host -v .:/var/tftpboot docker.io/pghalliday/tftp

This command will serve files from your current working directory via TFTP. In addition, you can use Wireshark to monitor that interface to actually see what’s happening.