Port forwarding for a Factorio server
A single UDP port. No game on this site is simpler to network than Factorio: no query port, no second socket, no split between protocols to get wrong.
Your setup
Choose the firmware family rather than your exact model — every router in a family shares the same menus.
Out of the box it is 34197. If you changed that, use whatever you set in --port.
The local address of the computer that runs the server. Find it with ipconfig on Windows or ip addr on Linux; it will begin with 192.168, 10. or 172.
Open these
Your firmware takes ranges, so each line here is one rule.
- 34197 UDP
34197UDPGame trafficOne UDP port, nothing else. Factorio is the simplest forward on this list.
Do not open these
Good news: this game has no remote-admin port that could be exposed by mistake. Forward the ports on the left and stop there.
Step by step: your router
- 1
Give the server a fixed local IP
A forwarding rule targets a single local address. If the server comes back from a reboot with a new one, the rule quietly points at an empty address — which is how forwards seem to "break by themselves".
On this router:look for DHCP Reservation, Address Reservation, Static Lease or Manually Assigned IP
- 2
Open the router admin page
From a device on the same network, open one of these in a browser:
- 192.168.0.1
- 192.168.1.1
- 192.168.2.1
- 10.0.0.1
Almost always printed on a sticker on the router itself.
- 3
Find the port forwarding page
Port Forwarding, Virtual Server, NAT, Applications & Gaming, or Port Mapping
Vendors use at least six names for the same feature. Whatever it is called, the page you want is the one asking for a port, a protocol and a device on your network. If the external and internal port fields both exist, set them to the same number.
- 4
Create one rule per line
a description field, if there is one External / WAN / Public / Service port Internal / LAN / Private port Protocol Internal IP / Device / Server IP Factorio 34197 34197 UDP your server’s local IP Use the same number for the external and internal port. You can make the external one different, but then every player has to connect on that new number, so keep them identical unless you have a specific reason not to.
- 5
Let the server through its own firewall
The router is now sending traffic to the right computer, but that computer can still turn it away. Windows Defender Firewall is the usual offender: it blocks a newly installed dedicated server by default, and from outside that is indistinguishable from a broken forward.
Take it with you
Factorio — port forwarding rules -------------------------------- 34197 UDP -> <server local IP>
Check whether it worked
Always test from outside your network. A connection from another device in the house proves nothing: that traffic stays on your LAN and never passes through the rule you just created.
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The usual mistake
Many groups never touch their router, because Factorio's matchmaking is usually able to negotiate a path through both ends by itself. When friends can already join a game you host from the client, adding a forward buys neither speed nor reliability. It only becomes a requirement with a headless server, which skips matchmaking entirely.
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Skipping port forwarding
A headless server keeps the factory producing overnight, and for Factorio that is much of the attraction. That is also where the port stops being optional.