Port forwarding for a Arma 3 server
Starting at the game port, Arma 3 claims four UDP ports in sequence. In order they carry gameplay, the Steam query, registration with the master server, and in-game voice.
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 2302. 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.
- 2302-2305 UDP
2302UDPGame trafficThe port players type.2303UDPSteam queryArma places its query port at game port + 1.2304UDPSteam masterRegistration with the master server list.2305UDPVONVoice-over-network. Skip it and in-game voice fails while everything else works.
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 Arma 3 2302-2305 2302-2305 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
Arma 3 — port forwarding rules ------------------------------ 2302-2305 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.
Advertisement
The usual mistake
Port four is voice over network, and leaving it shut produces a baffling symptom: the game works, everyone plays together, and nobody can hear a thing. Since voice problems are so easily put down to settings or headsets, this can go unnoticed for ages. Forward the full block.
Advertisement
Skipping port forwarding
Arma leans unusually hard on single-core speed, so the machine counts for more than the connection. A full modded Altis server is not a job for a spare laptop.