AT&T BGW320 Port Forwarding for Game Servers (NAT/Gaming)

On an AT&T Fiber BGW320 (and the older BGW210) you open game server ports at http://192.168.1.254: go to Firewall, then NAT/Gaming, enter the Device Access Code printed on the gateway's label, create the ports under Custom Services, then assign them to your server PC under Hosted Applications and click Save. The two step setup is where most people go wrong: making the service is not enough, you have to attach it to a device too.

How AT&T's setup differs

Most routers have one "port forwarding" form. AT&T splits it in two:

• A Custom Service is a named list of ports and a protocol, for example "Valheim, 2456 to 2457, UDP". It is not tied to any device.
• A Hosted Application is that service pointed at one device on your network. This is the part that actually forwards traffic.

You can only host a given service on one device at a time, and AT&T will refuse a second service that overlaps ports already in use.

Step 1: Sign in to the gateway

1. Connect to the gateway's Wi-Fi or plug in with Ethernet.
2. Open http://192.168.1.254 in a browser.
3. Click Firewall in the top menu, then NAT/Gaming.
4. Enter the Device Access Code when asked. It is the code printed on the side label of the gateway, not your Wi-Fi password.

The Smart Home Manager app and website can also forward ports on many accounts, but the local page shows every option and works even if you are not signed in to an AT&T account.

Step 2: Create the Custom Service

1. On the NAT/Gaming page click Custom Services.
2. Service Name: something you will recognize, like Rust server.
3. Global Port Range: the first and last port. For a single port put the same number in both boxes.
4. Base Host Port: the port the server listens on inside your network. For game servers this is the same as the first global port.
5. Protocol: TCP, UDP or TCP/UDP.
6. Click Add, then Return to NAT/Gaming.

A few common examples:

If a game uses ports with gaps between them, create a separate service for each, then host each one on the same PC.

Step 3: Host it on your server PC

1. Back on NAT/Gaming, choose your new service in the Service drop down.
2. In Needed by Device, choose the server PC by name or IP address.
3. Click Add. The rule appears in the Hosted Applications list.
4. Click Save if your firmware shows a save button.

Do this for every service you created.

Step 4: Keep the PC on the same address

The hosted application follows the device, but it helps to give the PC a fixed address so nothing moves around. On the BGW320 go to Home Network, then IP Allocation, find the server PC and choose Allocate with a fixed address from the list. Then confirm the hosted application still points at it.

Step 5: Turn off the things that get in the way

The BGW320 has a few security features that can quietly drop game traffic.

• Firewall Advanced (under Firewall): options such as Drop Fragmented Packets and flood detection exist here. Large UDP game packets can arrive fragmented, so if players connect and then time out, try turning off fragment dropping as a test.
• Packet Filter: if someone set filters before, they apply before NAT/Gaming rules. Make sure nothing blocks your game ports.
• UPnP: found under Firewall, then Firewall Advanced. It can stay on for consoles, but a manual hosted application is more reliable for a server.

Using your own router: IP Passthrough

Many people put a mesh system or gaming router behind the AT&T gateway. AT&T Fiber does not offer a pure bridge mode, but IP Passthrough does the job:

1. Go to Firewall, then IP Passthrough.
2. Set Allocation Mode to Passthrough.
3. Set Passthrough Mode to DHCPS-fixed.
4. Choose your own router's MAC address under Passthrough Fixed MAC Address.
5. Save and restart your own router.

Your router now gets the public IP directly, and you forward ports only on your router. Do not also create hosted applications on the gateway. Turn off the gateway's Wi-Fi so devices do not end up on two networks. If you skip passthrough you are in double NAT territory; our double NAT guide explains why that breaks game servers.

Testing

Start the server, then test from outside your network. A friend joining is the best test. A phone with Wi-Fi off works for TCP ports through a port checking website. Most game ports are UDP, which online checkers cannot read reliably; see how to test if a UDP port is open.

The public address to give friends is on the gateway's Broadband, then Status page under IPv4 address. AT&T Fiber gives each home a public IPv4, but it is dynamic. Pair it with a DDNS hostname so friends do not need a new IP each time it changes.

Common AT&T problems

• "Service conflicts with an existing service": another custom service or a preset already uses one of those ports. Delete the old one or remove its hosted application first.
• Server PC missing from Needed by Device: it is not connected right now, or it is behind your own router. Connect it directly or use IP Passthrough.
• Works for a few minutes, then drops: check the Firewall Advanced settings above and your PC's power settings.
• Friends get timeouts, you join fine on LAN: Windows Firewall on the server PC. Follow Windows Firewall rules for a game server.

The no router option

If clicking through Custom Services and Hosted Applications every time you try a new game sounds tiring, a hosted server avoids it. Your server gets its own address with its ports open, your home IP never reaches other players, and the world stays online when your PC is off. On GamezServers you can switch to a different game from the panel later, so one plan covers whatever your group plays next. Start with rent a game server.

FAQ

Where is the Device Access Code on a BGW320?

On the label on the side of the gateway, next to the Wi-Fi name and password. It is a separate code from both.

Does AT&T Fiber use CGNAT?

AT&T Fiber gives homes a public IPv4 address, so forwarding works. AT&T Internet Air (the fixed wireless service) is different and is often behind carrier NAT; see how to tell if you are behind CGNAT.

Can I use DMZ instead of port forwarding?

You can point IP Passthrough at a PC instead of a router, which acts like a DMZ, but it exposes every port on that PC to the internet and takes the PC off normal NAT protection. Opening only the game's ports is safer.

Does the BGW210 work the same way?

Yes. The menus, Device Access Code and Custom Services flow are the same on the BGW210 and BGW320.