Wired internet not working, but Wi-Fi is: a full breakdown of the reasons

It's quite common for a wireless network to distribute traffic to smartphones and tablets, but a desktop computer connected via cable can't see the network. This can be confusing: router The cable is functioning and there's access to the global network, but why is one of the LAN ports not working? The problem could lie in the physical integrity of the cable or in software conflicts within the operating system.

Diagnosis must begin with an understanding that Wi-Fi and a wired connection use different physical interfaces and are often handled independently by the network stack. While the wireless module automatically obtains an address and authenticates successfully, Ethernet adapter It may be in an error state, have incorrect settings, or have a physical line break. It's important not to panic and to check each connection level sequentially, from the cable connector to the TCP/IP protocol settings.

In most cases, the problem is resolved by rebooting the equipment or simply replacing the patch cord, but there are more complex scenarios that require adjusting the network card settings. Below, we'll detail the main reasons why wired Internet may be unavailable when Wi-Fi is active, and we will offer step-by-step troubleshooting instructions.

⚠️ Attention: Before running a deep diagnostic, be sure to perform a full reboot of your router and computer. Unplug the router for 10-15 seconds, then plug it back in. This will clear any temporary errors in the ARP table and DHCP server.

Physical problems with cables and ports

The most common, but often ignored, reason is damage to the cable itself. UTP or oxidation of the contacts. Unlike a wireless signal, which is either present or absent (with varying speeds), a wired connection requires the physical integrity of all eight strands of the twisted pair to fully operate at gigabit speeds. If the cable is pinched, frayed, or has microcracks in the insulation, the connection may not be established at all.

Check the LED indicators next to the RJ-45 connector on your computer's network card and on the router port. If the lights don't light or blink when you connect the cable, there's no electrical contact. Try connecting the cable to a different port. LAN port on the router, since a specific port could have burned out or failed.

• 🔌 Check that the connector fits tightly into the socket - the connector should click when inserted.
• 🔍 Inspect the cable along its entire length for any strong kinks or marks from furniture.
• 🔁 Try using a different patch cord to rule out its malfunction.

In addition, connectors can oxidize, especially if the equipment is located in a damp room or near a window. Metal contacts inside RJ-45 Over time, these contacts become dull, increasing resistance and leading to packet loss or a complete loss of the link. In such cases, careful cleaning of the contacts or replacement of the cable can help.

Network card or driver failure

If the cable is fine, the problem may lie in the software that controls the network adapter. Drivers These are the intermediaries between the operating system and the hardware. If they are outdated, damaged after a Windows update, or conflict with other software, the network card stops correctly processing incoming signals, even if it is physically intact.

You can check the device status via device Manager. Press the key combination Win + R, enter the command devmgmt.msc and press Enter. In the window that opens, find the "Network Adapters" section. If you see a yellow triangle with an exclamation point next to the name of your card (for example, Realtek PCIe GBE Family Controller), the system recognizes the device but cannot start it.

In some cases, a complete reset of the adapter's settings helps. In the same Device Manager, right-click the network card and select "Uninstall device." Then, restart the computer. Upon startup, the system will attempt to automatically reinstall the driver, which often fixes software errors. It's also worth checking whether the card is disabled by software: in the window ncpa.cpl (opens in Win + R) Make sure the "Ethernet" adapter is not grayed out.

IP address conflict and DHCP settings

One of the most common logical reasons why wired Internet If the router isn't working, there's a problem obtaining an IP address. The router acts as a DHCP server, distributing addresses to all connected devices. If the address pool is exhausted or a conflict occurs (two devices are trying to use the same IP address), the connection will fail.

Users often manually assign static IP addresses to speed up their networks. When changing routers or moving to a new office, these settings become irrelevant because the new gateway uses a different address range. As a result, the computer searches for the network using the old coordinates, but doesn't find the desired segment.

To fix the situation, you need to return the settings to automatic. Go to Control Panel → Network and Internet → Network and Sharing Center → Change adapter settingsRight-click on "Ethernet" and select "Properties." Find it in the list. Internet Protocol version 4 (TCP/IPv4), select it, and click "Properties." Make sure "Obtain an IP address automatically" and "Obtain DNS server address automatically" are checked.

⚠️ Attention: If your provider requires MAC address binding or uses specific VLAN settings, automatic mode may not work without first registering the equipment in your personal account.

Restrictions from the provider

Keep in mind that your internet service provider may block access from new devices. Many providers use tethering. MAC address The first device connected when signing the contract. If you previously used only a Wi-Fi router and now connect your computer directly via cable (or replace your router), your provider may not assign an IP address to the new device.

In this case, Wi-Fi continues to work because the router is already authorized on the provider's network, and the new cable coming from the PC is ignored. There's only one solution: cloning the MAC address or calling technical support to re-bind it. Your provider may also limit the number of connected devices on your plan, and your PC may simply be the "redundant" one.

How to find out the MAC address of a network card?

To do this, open the command prompt (cmd) and enter ipconfig /all. Find the "Physical Address" line in the section for your Ethernet adapter. This is the MAC address that your ISP sees.

In addition, some operators block the work of their own routers Users in Bridge mode require their own equipment. If you try to connect your PC via cable to a provider's modem that isn't configured as a router, you won't be able to connect to the internet without additionally configuring a PPPoE connection on your computer.

Router settings and network separation

Modern routers allow for flexible port configuration. It's possible that a specific LAN port has been disabled by the administrator or switched to IPTV mode in the device's settings. In this case, even with a working cable, the port won't assign IP addresses or transmit data to the internet, functioning only to receive the video stream from the set-top box.

Check your local network settings in your router's web interface (usually at 192.168.0.1 or 192.168.1.1). The sections may be called LAN Setup, Network or Local NetworkMake sure the DHCP server is enabled and has a free address pool. If the DHCP client limit is set to 1 or 2, and you already have many devices connected via Wi-Fi, your computer will simply run out of room in the queue.

• 📡 Check if the "Guest Network" mode is enabled for Wi-Fi only.
• 🔒 Make sure that Parental Controls that block your PC on a schedule are not activated.
• ⚙️ Reset your router to factory settings if the configuration is too complicated.

The impact of antivirus and firewall

Third-party antivirus suites (Kaspersky, ESET, Avast, etc.) often have built-in firewalls that can block connections to new networks, detecting them as "Public." If the network profile is set incorrectly, the firewall can block all incoming and outgoing traffic, creating the illusion that there is no internet connection.

Try temporarily disabling your antivirus and Windows Firewall to test this hypothesis. If the internet connection returns, you'll need to add your home network to the trusted list in your security software settings. Switching the network type from "Public" to "Private" in Windows settings often helps.

⚠️ Attention: Antivirus and operating system interfaces are constantly updated. The location of network type switches may differ in different versions of Windows 10 and 11. Always consult the software developer's latest help documentation.

DNS and TCP/IP stack failures

Sometimes there is a physical connection (status "Connected"), but websites don't open, but instant messengers work. This is a classic sign of problems with DNSThe computer can't resolve a website name (e.g., google.com) to an IP address. Wi-Fi may work at this point if other DNS servers are specified or the cache is still valid.

To resolve the issue, we recommend clearing the DNS cache and resetting the TCP/IP stack. Open a command prompt as administrator (search for "cmd" in the search bar, right-click, and choose "Run as administrator") and enter the following commands one by one, pressing Enter after each:

ipconfig /flushdns
ipconfig /registerdns
ipconfig /release
ipconfig /renew
netsh winsock reset

After executing the last command netsh winsock reset A computer restart is required. This command restores the Winsock directory, which manages network connections in Windows. Damage to this directory is often the cause of a wired adapter "hanging" in the identification state.

Comparison Analysis: Wi-Fi vs. Cable

Understanding the differences in architecture helps us find the problem faster. Wi-Fi is a half-duplex medium, susceptible to interference but flexible in configuration. Cable is full-duplex and stable, but demanding in terms of its physical properties. When Wi-Fi is present but cable is not, we rule out issues with the ISP (since the link to the router is still active) and focus on the "router-to-PC" connection.

The table below lists key differences that aid in diagnosis:

Why is the yellow triangle "No Internet Access" lit?

A yellow triangle means there's a physical connection to the router (the cable is intact, the ports are working), but the router is blocking the computer from accessing the outside world. This is almost always a problem with IP or DNS settings, or is blocked by your ISP or antivirus software.

Can a network card be damaged by a thunderstorm?

Yes, this is a common cause. If a lightning strike hits a provider's line, the WAN port on the router is usually the first to burn out, but the surge can travel further and damage LAN ports or even the computer's network card. If Wi-Fi is working, then the router's WAN port is intact, but the LAN port could have been damaged separately.

Is it worth buying a USB-LAN adapter?

If the integrated network card is faulty or malfunctioning, an external USB adapter (even a cheap one) is an excellent temporary or permanent solution. It takes the load off the network and is often more stable than the integrated solutions found in older motherboards.

Does cable length affect performance?

The Ethernet standard (twisted pair) guarantees stable operation over distances of up to 100 meters. If your cable is shorter (which is common in apartments), the length isn't a problem, unless it's located near strong sources of electromagnetic interference.