can i use the asus rt-ax86u with a dsl modem? i have at&t u-verse.

Diagnosis

The ASUS RT-AX86U is a standalone wireless router, not a modem. Because AT&T U-verse delivers internet via a DSL (Digital Subscriber Line) or Fiber connection, you cannot plug the phone line or fiber optic cable directly into the RT-AX86U. You must have a gateway or modem that acts as the bridge between the ISP's signal and the router's Ethernet WAN port. The primary conflict occurs because AT&T U-verse gateways (like the Pace 5268AC or BGW210) are "combo" units that act as both a modem and a router. If you simply plug the RT-AX86U into the gateway, you create a "Double NAT" (Network Address Translation) scenario. This happens when two routers are fighting to assign IP addresses to your devices, which leads to high latency in gaming, broken port forwarding, and intermittent connectivity drops. To confirm this is happening, check if your RT-AX86U WAN IP address starts with 192.168.x.x; if it does, you are in a Double NAT state.

How to Fix It

To properly integrate the RT-AX86U with AT&T U-verse, you must put the AT&T gateway into "Passthrough Mode" to disable its routing functions and allow the ASUS router to handle all traffic.

1. Power down both the AT&T gateway and the ASUS RT-AX86U.
2. Connect a high-quality Cat6 Ethernet cable from one of the yellow LAN ports on the AT&T gateway to the blue 2.5G WAN port on the back of the RT-AX86U.
3. Power on the AT&T gateway and wait for the "Broadband" or "Internet" light to turn solid green.
4. Connect a computer to the AT&T gateway via Ethernet or WiFi and navigate to 192.168.1.254 in your browser.
5. Navigate to the Firewall tab, then select Passthrough.
6. Find DHCP Passthrough and change the setting to "On."
7. Look for Packet Filter Passthrough and set it to "On."
8. Save the settings and restart the gateway.
9. Power on the RT-AX86U. Open the ASUS Router app or go to router.asus.com.
10. During the Quick Internet Setup (QIS), select Automatic IP as the connection type. The RT-AX86U should now pull a public IP address directly from AT&T.

If That Didn't Work

• Disable Gateway Wireless: If you still experience interference or "ghost" networks, manually log back into the AT&T gateway (192.168.1.254) and turn off the 2.4GHz and 5GHz wireless radios entirely. This ensures your devices only connect to the RT-AX86U's WiFi 6 signal and prevents signal overlap.
• Static IP Assignment: If the RT-AX86U fails to pull an IP, assign a static IP to the ASUS router within the AT&T gateway's LAN settings. Use an IP like 192.168.1.10 and ensure the subnet mask is 255.255.255.0.
• DMZ Setup: If "Passthrough Mode" is unavailable on your specific gateway model, find the DMZ (Demilitarized Zone) setting in the AT&T interface. Enter the WAN IP address assigned to the RT-AX86U into the DMZ field. This pushes all incoming traffic directly to the ASUS router, bypassing the gateway's firewall.
• Factory Reset Loop: If the RT-AX86U keeps reverting to a "WAN disconnected" state, perform a hard reset by holding the reset button for 10 seconds, then re-run the setup while the AT&T gateway is already fully booted and synced.

Heads Up

• Avoid Port 1: Always use the dedicated blue WAN port for the modem connection; using the LAN ports for internet input requires a complex "LAN-to-WAN" software conversion that degrades performance.
• Cable Quality: Use Cat6 or Cat6a cables. Using old Cat5 cables will bottleneck your U-verse connection to 100Mbps, wasting the RT-AX86U's gigabit capabilities.
• Firmware Sync: Immediately update the ASUS firmware to the latest version via the "Administration" tab to ensure compatibility with the latest AT&T gateway security protocols.
• Gaming Port: If you use the dedicated Gaming Port on the RT-AX86U, remember that this port takes priority over all other traffic; ensure your primary gaming PC is plugged here for the lowest latency.