R.E.P.O. Friends Can't Join? NAT & Firewall Guide
If your R.E.P.O. lobby will not connect, first work out whether the problem is your network or the game session itself. Common symptoms include friends being unable to join, hosting failing, players disconnecting after joining, loading getting stuck, or Steam invites opening without a real connection.
Do not start by forwarding random ports. R.E.P.O. does not publish a traditional dedicated-server port table, so broad router changes are a poor first fix. Check NAT type first, then move through firewall, Steam, VPN, version, and mod checks.
First decide where the failure is
R.E.P.O. connection failures are not all router problems. First separate the symptom: the host cannot create a session, friends cannot join this host, one friend fails while others can join, or everyone joins but disconnects after loading.
- Only one host fails: check that host network, firewall, Steam state, VPN, and virtual adapters.
- Only one friend fails to join: check that friend client, version, mods, VPN, and local firewall.
- Everyone fails with this host: test NAT on the host PC and consider letting another player host.
- Players join and then disconnect: check version, mods, game stability, and security software before changing router rules.
If outside connections fail, check NAT and public reachability
Run the test on the same device and network you use for R.E.P.O.. The result helps separate ISP/router reachability from game, firewall, and platform problems.
| Result | Meaning for hosting or co-op | Next step |
|---|---|---|
| Full Cone / Open | Usually suitable for inbound connections or direct sessions. | Check firewall, ports, server config, and game version. |
| Restricted / Port Restricted | May work, but success can vary by game and peer. | Try UPnP or manual forwarding, then retest. |
| Symmetric NAT | Often unreliable for peer-to-peer or home-hosted sessions. | Disable VPN/proxy tools, change networks, or use hosting/relay. |
| CGNAT / no public IPv4 | The public internet usually cannot reach your home router. | Ask for public IPv4, or use a VPS, hosted server, or relay. |
If outside players can reach the host, apply the game-specific fix
R.E.P.O. does not publish a traditional dedicated-server port table, so the next step is not to open random ranges. If the NAT result is good enough for hosting, focus on the host PC and Steam session path.
- Allow R.E.P.O. through Windows Defender Firewall on the active network profile.
- Turn off VPNs, proxies, gaming accelerators, campus network clients, and unused virtual adapters.
- Make sure every player uses the same game version.
- Disable mods for one clean test if the group normally plays modded.
If direct joining works but the symptom remains, check the next layer
At this point the basic network path is less likely to be the only blocker. Treat Steam invites, lobby state, version mismatch, and mod mismatch as the next layer.
- Restart Steam and the game on both host and joining players.
- Try a fresh lobby instead of reusing a failed invite.
- Try a different host. If the problem follows one host, that host network or firewall is the likely layer.
- If only modded sessions fail, treat the mod set as the main suspect.
When router changes will not fix it
This is the stop condition for router work. If the game has no official fixed port requirement for your setup, repeating port-forwarding changes can add risk without proving the cause.
- The host is behind CGNAT or has no public IPv4.
- The host has Symmetric NAT and another player has a better NAT result.
- The issue only happens with one client, one mod set, or one Steam invite path.
- You are considering broad port ranges or DMZ only to test one co-op game.