Port 69 — TFTP

Q: How do I check if port 69 is open?

Locally, sudo lsof -i :69 on macOS or Linux, or netstat -ano | findstr :69 on Windows. From outside, nc -zv host 69 tells you whether anything answers.

UDP well-known

What runs on port 69

Trivial FTP, used for network boot and switch firmware.

Trivial FTP has no authentication whatsoever by design and runs over UDP. It exists because it is small enough to fit in the boot ROM of a device that has no operating system yet, which is why it is still used for PXE network boot and for pushing firmware to switches and phones. It should exist only on an isolated provisioning network and should never be reachable from anywhere else.

Security considerations

No authentication at all by design. Confine it to an isolated provisioning network.

Checking whether something is listening

# Linux / macOS — what is bound to the port
sudo lsof -i :69
sudo ss -lntp | grep :69

# Windows
netstat -ano | findstr :69
Get-NetTCPConnection -LocalPort 69

# is it reachable from outside?
nc -zv example.com 69
curl -v telnet://example.com:69

Freeing the port

# find the process, then stop it
sudo lsof -ti :69 | xargs kill        # Linux / macOS
netstat -ano | findstr :69            # note the PID, then:
taskkill /PID <pid> /F                    # Windows

Should this port be open to the internet?

Usually not. Expose it only if a specific external client needs it, and restrict by source address where you can.

Opening or blocking port 69

Finding the port is usually the first half of the job. Start narrow — the second rule is there for services that genuinely serve the public, and most do not:

# ufw — Debian, Ubuntu
sudo ufw allow from 10.0.0.0/8 to any port 69 proto udp
sudo ufw allow 69/udp                   # only if it genuinely serves the public

# firewalld — RHEL, Fedora, CentOS
sudo firewall-cmd --permanent --add-rich-rule='rule family=ipv4 source address=10.0.0.0/8 port port=69 protocol=udp accept'
sudo firewall-cmd --reload

# iptables, if you are still there
sudo iptables -A INPUT -p udp --dport 69 -s 10.0.0.0/8 -j ACCEPT
sudo iptables -A INPUT -p udp --dport 69 -j DROP

# Windows
New-NetFirewallRule -DisplayName "TFTP 69" -Direction Inbound -Protocol UDP -LocalPort 69 -RemoteAddress 10.0.0.0/8 -Action Allow

10.0.0.0/8 stands in for a private range — substitute your own. Note that a firewall rule does not undo a service bound to 0.0.0.0; it only stops packets reaching it, and a misconfigured or disabled firewall then exposes it immediately.

Quick reference

Port	69
Protocol	UDP
Service	TFTP
Range	Well-known (0–1023) — binding requires root on Unix

Frequently asked questions

What is port 69 used for?

Trivial FTP, used for network boot and switch firmware.

Is it safe to open port 69?

No authentication at all by design. Confine it to an isolated provisioning network.

How do I check if port 69 is open?

Locally, sudo lsof -i :69 on macOS or Linux, or netstat -ano | findstr :69 on Windows. From outside, nc -zv host 69 tells you whether anything answers.

Why do I get "address already in use" on port 69?

Another process is bound to it — often a previous run of your own program that did not exit cleanly. Find it with lsof -ti :69 and stop it, or configure your application to use a different port.

Can I change the port this service uses?

Almost always yes, in the service's configuration. Moving off a default port reduces automated scan noise, but it is obfuscation rather than security — a real attacker scans all 65,535.

Other common ports

All port numbers