Why the wired internet connection is gone, but Wi-Fi is working: a complete diagnosis of the problem

You turned on your computer, and the internet via cable suddenly disappeared - and Wi-Fi on your phone or laptop works without any problems.This situation is familiar to many, but not everyone knows how to quickly restore the connection. In 80% of cases, the problem can be resolved within 5-10 minutes if you know where to look for the root cause. In this article, we'll examine all possible causes—from a simple cable break to errors in the router or ISP settings.

It is important to understand: when Wi-Fi is working, and there is no wired internet, this indicates local malfunction — either on your device or between the router and it. Your ISP has nothing to do with it (unless they block MAC addresses). We've compiled a diagnostic checklist to help you identify the culprit, from the simplest to the most complex. We'll start with checking the physical connections and finish with analyzing the network protocols.

Let us warn you right away: if you are not sure about your actions, Do not reset your router to factory settings—this may worsen the problem, especially if your provider binds your internet connection to the device's MAC address.It's best to follow the instructions in order and record your changes after each step.

1. Checking physical connections: cable, ports, indicators

Start with the most obvious - inspection of cables and connectorsEven a microscopic break in a wire or dirty contacts can interrupt the connection, while Wi-Fi will continue to work through the router's antennas. Here's what to do:

• 🔌 Reconnect the cable to the port LAN On the router and PC network card. Sometimes the connection weakens due to vibration or overheating.
• 🔍 Check the indicators On the router: are the port lights on? LAN (usually yellow/green)? If not, the problem is in the cable or port.
• 🔄 Try a different cableIdeally, one that is known to be working (for example, the one that comes with the router).
• 🖥️ Connect the cable to another device (laptop, Smart TV). If the internet works, the problem is with your PC.

Pay special attention RJ-45 connectors (The plastic "plugs" at the ends of the cable). If you see any bent or oxidized contacts, you can carefully straighten them with a thin screwdriver. Also, check that the cable isn't pinched under furniture—broken wires often cause signal interruptions.

⚠️ Attention: If you use extension cord or splitter For a network cable, temporarily connect your PC directly to the router. These devices often become a "weak link" due to poor connections.

2. Diagnostics of the network card on a PC or laptop

If the cable is fine but there is still no internet, the problem may be in network adapter your device. Here's how to check:

• 💻 Open Device Manager (Win + X → Device Manager) and find the section Network adapters.
• 🔄 Update your driver network card: right-click on the adapter (for example, Realtek PCIe GbE Family Controller) and select Update driver.
• 🔧 Disable and enable the adapter: right click → Disconnect the device, then turn it on again.
• 🔄 Reset TCP/IP settings via command line (administrator):

  netsh int ip reset
  netsh winsock reset

It is also worth checking whether the network card is disabled in BIOS/UEFI (relevant for PC). Go to the motherboard settings (usually by pressing Del or F2 at boot) and make sure that the parameter Onboard LAN or Ethernet Controller included (Enabled).

Make sure the cable is connected to the Ethernet port (not USB or another port)

Check the adapter's status in the Device Manager (there is no exclamation mark)

Update driver manually or via Windows Update

Reset TCP/IP stack via command line

Restart your PC after changes-->

⚠️ Attention: If you have recently updated Windows or installed new programs (especially VPNs or antiviruses), they could block the network connection. Try rolling back your system to a previous restore point.

3. Router settings: why the LAN port may be disabled

Sometimes the problem lies in the settings of the router itself. For example, The LAN port can be disabled programmatically., or it has incorrect VLAN settings. Here's what to do:

• 🌐 Log into the router's web interface (usually at the address 192.168.1.1 or 192.168.0.1, login/password — admin/admin or indicated on the sticker).
• 🔧 Check the status of LAN ports in the section Network → LAN or Local Network. Make sure the port is not disabled (Enabled).
• 🔄 Reset MAC binding (if your provider uses it for authorization). Find the section MAC Clone or Bound MAC and remove all bindings.
• 📡 Update your router firmware (chapter Administration → Firmware Upgrade). Outdated software may conflict with modern devices.

If you have dual-band router (For example, ASUS RT-AX88U or TP-Link Archer C6), check if the mode is turned on Bridge or Repeater — in this case, the LAN ports may work differently. Also, some models (for example, Keenetic) allow you to assign ports to IP-TV, which may conflict with the regular Internet.

How to reset a router to factory settings if nothing else works

1. Find the button Reset (usually recessed into the body).

2. Press it with a paper clip and hold for 10-15 seconds until the indicators start flashing.

3. After resetting, configure the router again using the data from your provider (login/password for PPPoE or MAC address).

⚠️ Warning: This will delete all user settings, including your Wi-Fi password!

4. Problems on the provider's side: blocking and restrictions

Even if Wi-Fi is working, it doesn't always mean the ISP isn't the problem. Some operators use separate policies for wired and wireless trafficHere's what might happen:

• 🔒 MAC address blockingYour ISP has bound your internet connection to the router's MAC address, but not to your PC. In this case, your wired connection won't work until you clone the MAC address or add a new address in your account.
• 📉 Port speed limitation: Some tariffs split traffic between Wi-Fi and LAN (for example, Rostelecom or Beeline in business rates).
• 🔄 PPPoE authorization failed: If the router is configured to connect automatically, but a separate PPPoE client is running on the PC, a conflict will occur.
• 🛡️ Parental Control or filtering: In the router settings, you can enable scheduled access restrictions only for wired devices.

To check for MAC blocking, connect the cable directly to your PC (bypassing the router) and try to obtain an IP address automatically. If the internet doesn't appear, but Wi-Fi works through the router, your ISP is most likely using tethering. Solution:

1. Find out the MAC address of the router (on the sticker or in the web interface).
2. Clone it to the PC network card (in the adapter settings or via regedit).
3. Or add the PC's MAC address in your provider's personal account.

⚠️ Attention: Some providers (eg. MGTS or Dom.ru) plans with "separate internet" for TV and PC. In this case, the LAN port can be assigned to IPTV, while only Wi-Fi is used for internet. Check the terms in your contract.

Rostelecom

Beeline

MGTS

Dom.ru

Yota

Other-->

5. IP address conflicts and DHCP errors

If your PC is not receiving IP address automatically From the router, the connection won't be established, even if the cable is working properly. Symptoms:

• A yellow triangle with an exclamation mark is displayed in the tray.
• IN ipconfig /all (command line) address type 169.254.x.x (this means that DHCP did not work).
• Message "Network without internet access".

Solutions:

1. Restart the DHCP service on the router (section DHCP Server → turn it off and on again).
2. Assign IP manually:

   IP address: 192.168.1.100
   Mask: 255.255.255.0
   Gateway: 192.168.1.1 (router address)
   DNS: 8.8.8.8 (Google) or 1.1.1.1 (Cloudflare)

3. Clear your DNS cache:

   ipconfig /flushdns

4. Disable additional network adapters (VPN, virtual machines) that may conflict.

If the problem occurs only on one PC, and other devices via cable work fine, the fault is conflict in Windows settingsTry creating a new network profile:

1. Open Settings → Network & Internet → Ethernet.
2. Click Managing known networks and delete the current profile.
3. Reconnect the cable - Windows will create a new profile.

6. Viruses, firewalls and third-party software

Few people realize that antiviruses, VPN clients, or even Windows updates can block a wired connection without affecting Wi-Fi. Reasons:

• 🛡️ Windows Firewall or third-party firewall (For example, Kaspersky, ESET) blocks traffic over Ethernet.
• 🦠 Mining viruses, which "hide" network activity under Wi-Fi, but block a wired connection.
• 🔄 VPN programs (For example, NordVPN, ProtonVPN) can redirect all traffic through the virtual adapter.
• 🔧 Group Policy Settings (relevant for work PCs in a domain).

How to diagnose:

1. Boot into Safe Mode with Networking (F8 when loading or through msconfig). If the Internet appears, the software is to blame.
2. Disable your antivirus and firewall for 5 minutes and check the connection.
3. View active connections through Resource Monitor (Win + R → resmon), tab Net.
4. Remove suspicious programs from Autoloads (through Task Manager).

If you suspect a virus, check your PC with utilities KVRT (from Kaspersky) or Dr.Web CureIt!. It's also worth checking the file. hosts (path: C:\Windows\System32\drivers\etc\hosts) for the presence of suspicious entries.

7. Hardware malfunctions: when repairs are essential

If all the previous steps did not help, it is possible hardware failureHere are the most common scenarios:

• 🔌 Burned out LAN port on the router (for example, after a thunderstorm or power surge). Symptoms: the port does not light up, the cable does not lock.
• 💻 Faulty network card on a PC (especially if it is built into the motherboard).
• ⚡ Problems with the router power supply - It may not provide enough power to operate all ports.
• 🔧 Oxidation of contacts on the PC motherboard or inside the router (relevant for damp rooms).

How to check:

1. Connect the router to a different power source (if there is a spare unit with suitable parameters).
2. Check the router port with a multimeter (if you have the skills): there should be a resistance of ~100 Ohm on contacts 1–2 and 3–6.
3. Use an external network card (USB-Ethernet adapter) for a PC. If the internet works with it, the integrated card is to blame.

If your router is under warranty, contact a service center. For a PC, you can try reinstalling the network card in a different PCI slot (if it's a discrete one). If the card is integrated, the only option is to repair or replace the motherboard.

⚠️ Attention: If your router gets hotter than usual or smells burnt, unplug it immediately! These are signs of a short circuit, which could cause a fire.

FAQ: Frequently Asked Questions

Can a virus block only wired internet without affecting Wi-Fi?

Yes, some viruses (such as miners or botnets) intentionally block Ethernet connections to hide their activity. They redirect traffic through Wi-Fi or virtual adapters. Check your system with utilities. KVRT or Malwarebytes.

Why did my cable internet disappear after updating Windows?

Updates often reset network adapter settings or install incompatible drivers. Try:

1. Roll back the network card driver (Device Manager → Properties → Roll Back Devices).
2. Delete last update (Settings → Update & Security → View update history).
3. Reset TCP/IP stack (commands) netsh int ip reset And netsh winsock reset).

The router shows the cable is connected, but there's no internet. What's wrong?

This is a typical sign of a problem at the level IP addressing or DHCPFirst, check if your PC receives an IP address:

1. Open command prompt and type ipconfig /all.
2. If the address type is 169.254.x.x — DHCP isn't working. Assign the IP manually (see section 5).
3. If the address 0.0.0.0 — the problem is in the driver or adapter.

Also make sure that it is not enabled in the router settings. Isolate LAN Clients (device isolation).

Can you use Wi-Fi as a bridge for a wired PC?

Yes, if your PC does not have a network card or it is broken, you can share the Internet from your phone/laptop via Wi-Fi, and then connect your PC to this network via USB-ethernet adapter or by Wi-Fi Direct (if your PC supports it). Alternatively, you can buy it. Powerline adapter (transmits internet through electrical wiring).

The provider says everything is fine on their end. What should I do?

If your ISP says the problem is on your end, follow these steps:

1. Connect the cable directly to your PC (bypassing the router). If the internet appears, the router is to blame.
2. Ask your provider re-register you on the network (sometimes the session "freezes").
3. Please check if they are applied MAC address restrictions or port binding.
4. If nothing helps, ask to send a technician to check the line at the physical level (break, interference).