Switched to Asus RT-AX57, lights show connected but not internet access

Understanding and Troubleshooting Router Connectivity Issues: A Case Study with Asus RT-AX57

Introduction

Upgrading or replacing networking equipment can often introduce unexpected challenges, especially for users new to network configuration. Recently, a user shared their experience with an Asus RT-AX57 router, encountering a common issue: the router’s status lights indicate a successful connection, yet internet access remains unavailable. This article aims to provide a professional overview of such issues, their possible causes, and effective troubleshooting strategies to resolve them.

Scenario Overview

The user replaced their ISP’s modem with a third-party Asus RT-AX57 router to achieve higher internet speeds, as their original modem seldom delivered the full 300 Mbps plan (often only around 100 Mbps or less). Post-installation, several key observations and attempts were made:

The Asus RT-AX57 was connected to the modem.
All router indicator lights showed a blue (connected) status.
Browsing attempts resulted in “Cannot connect to the internet” errors.
Directly connecting to the modem’s Wi-Fi yielded internet access, albeit at reduced speeds.
Configuring the Asus device as an Access Point did not resolve the issue.
Resetting the router and reverting to router mode did not improve connectivity.

Initial Context

The previous router, a TP-Link device, functioned correctly for approximately two hours before malfunctioning—prompting a replacement. The TP-Link was plug-and-play, providing internet access immediately. Conversely, with the Asus, despite apparent connection indicators, internet connectivity was absent.

Common Causes & Troubleshooting Steps

Verify Physical Connections and Setup
Ensure the router’s WAN port is correctly connected to the modem.
Confirm that the Ethernet cable used is functioning properly.
Check that the modem is powered on and functioning correctly.
Check Router Configuration
Confirm if the Asus RT-AX57 is set to obtain IP address and DNS automatically via DHCP.
If static IP or custom settings are used, verify the configurations match your ISP’s requirements.
Ensure that the router mode (Router vs. Access Point) aligns with your network topology.
Review Internet Connection Status
Access the router’s admin interface to check the WAN status.
Look for any error messages or failed connection attempts.
Some routers have logs indicating the reason for failed DNS or IP assignments.
Test Connection at More Fundamental Level
Connect a device directly