Yes. The RT-AX86U is compatible with DSL modems. The setup requires specific steps.
- Unplug the power cable from your DSL modem. If it has a battery backup, remove the battery.
- Connect the bundled network cable from your modem's Ethernet/LAN port to the blue WAN (Internet) port on the RT-AX86U.
- Power on your DSL modem. Check its LED lights to ensure the connection is active.
- Power on your RT-AX86U router.
IF THAT DIDN'T WORK: You will need your DSL username and password from AT&T (your ISP) to properly configure the router during the web setup at http://router.asus.com. The router cannot authenticate with AT&T without these credentials.