How to solve WiFi problem (Cannot connect to WiFi) [english]

By | 08/10/2021

Last Updated on 08/10/2021 by administrator

How to solve WiFi problem (Cannot connect to WiFi) [english]

Warning: The article does not focus on a thing like: “I’ll connect to WiFi, but not to the internet”. The article only solves the problem with WiFi, ie solving problems with the connection of WiFi stations (laptops, mobile phones, tablets, …), or problems with the home WiFi router.

Legend: In the article, the term WiFi station means any device that can be connected to a WiFi network (laptop, mobile phone, tablet, ..). In the article, the term WiFi station means any device that can be connected to a WiFi network (laptop, mobile phone, tablet, ..).

a) Only one WiFi station cannot connect to the WiFi network:

1. Is the WiFi network on the laptop deactivated?

The problem with WiFi can be caused by the button or keyboard shortcut that deactivated the WiFi card. If you cannot see the WiFi network or WiFi networks, it is possible that the WiFi card is deactivated. Usually on some key F2-F12 the icon of the transmitter or airplane is displayed, so the WiFi card can be activated by a combination of a keyboard shortcut such as Fn + F5. Older laptops usually have a special button for activating or deactivating it, and some have it on the side.

Problém s wifi (how to fix wifi)

2. Static IP address

The most of the WiFi stations use an IP address leased from a DHCP server on the WiFi router. It may happen that the IP address on the WiFi interface is “statically” assigned. In this case, follow the picture below:

Problém s wifi (how to fix wifi)

3. Restart the computer, laptop or other WiFi station

The fastest way to solve many problems.

4. Delete the old profile of the original WiFi network.

4.1. WIN10

Open the search by clicking on WIN + R and typing: ms-settings:network-wifisettings:

win+r

manage known networks shortcut

Search for the problematic WiFi network and click to Forget:

Forget network

Reconnect to WiFi (you must re-enter the authentication password if the wireless network is encrypted).

4.2. Android

Similarly, for mobile phones, it sometimes helps to delete WiFi from the list of known networks (Forget or Forget network) and reconnect again.

Forget network

5. Reset TCP/IP stack

See. previous article Problém s připojením do internetu

6. Check the settings in the BIOS / UEFI

When starting the computer, go to the BIOS / UEFI and check if WiFi (Wireless) is enabled. Disabling Secure Boot also solved the WiFi issue.

Note: Different BIOSes / UEFIs have different settings, so some of these two settings may not be findable in the BIOS / UEFI at all.

Secure Boot bios

wireless support bios

7. Network reset

In WIN 10, the keyboard shortcut WIN + X + W opens the Network status window. In the window below, click on Network Reset:

Resetování sítě (Network Reset)

Click Reset now to reinstall all network adapters to their default state:

Resetování sítě (Network Reset)

8. Update WiFi end station drivers

Reinstall the WiFi driver, or download the latest WiFi driver. For mobile devices, download the latest system updates.

b) One or more WiFi stations cannot connect to the WiFi network:

9. Unplug the WiFi router

Just unplug it from the electric outlet, and leave it unplugged for about 30 seconds (let the capacitors fully discharge). Thanks to the restart, the internal memory is completely erased and all running processes are terminated, where the remains of badly terminated programs and services can be found.

10. Wireless Channel change on WiFi router

Another problem with WiFi may be interference on the current channel.

If you cannot connect to the WiFi router and change the channel using wireless, connect via cable.

I recommend to download the application for Android Wifi Analyzer (for iOS there will definitely be an alternative as well) and according to the interference choose a new channel under desired wireless frequency:

  • For 2.4 GHz, choose channels 1, 6 or 11 (these are non-overlapping channels):
    • If there is a lot of interference with the above channels and it is necessary to choose really other than 1, 6 or 11, it is not recommended to choose 12 or 13 channels, as any WiFi network card originating from US will not connect to them (US WiFi network cards are not allowed to connect to 12 and 13 channels)
    • Keep in mind that 2.4 GHz is an unlicensed band and may be interfered with by other devices. I recommend reading the article How to increase WiFi signal in section 3 – “Where not to place WiFi routers”, where potential sources of interference are listed
  • For 5 GHz, select channels 36, 40, 44, 48 for several reasons:
    • There are also WiFi stations that do not support connection to channels other than 36, 40, 44, 48 – list here: https://clients.mikealbano.com/home
    • Channels 52, 56, 60, 64, 100-140 use the DFS function in Europe and can switch to another channel at any time when radar is detected, thus temporarily disconnecting all stations from the WiFi network.
      • In addition, when hiding the SSID of a network (Hide SSID or Disable SSID Broadcast option), it is not possible to connect to these DFS channels
    • Channels 149-165 can transmit in Europe only 1/8 of power (25mW vs 200mW) than the above – that means less WiFi signal coverage
  • Select 20MHz channel width for both bands. A smaller channel width is less likely to interfere with other channels.

Example settings for TP-Link:

Problém s wifi (how to fix wifi)

Note: I have tried the “Auto” channel mode on TP-Link in practice. Despite the interference from the neighboring WiFi channels, there was no channel switch to less disturbed. I do not recommend using.

11. Check the DHCP server

Verify that there is no other DHCP server on the network, which can be any device on the network that can assign other (fake) IP addresses.

11.1. How to test it:

If the WiFi router is managed under the web interface under the IP address 192.168.0.1, then the same IP address should be assigned for the Default Gateway and DHCP server on the Windows station. This can be found in the CMD command:

ipconfig /all

Output from ipconfig /all:

Wireless LAN adapter Wi-Fi:

Connection-specific DNS Suffix . : local
Description . . . . . . . . . . . : Intel(R) Centrino(R) Wireless-N 2230
Physical Address. . . . . . . . . : 60-6C-66-60-F1-53
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
IPv4 Address. . . . . . . . . . . : 192.168.0.247(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Lease Obtained. . . . . . . . . . : pátek 8. května 2020 10:40:21
Lease Expires . . . . . . . . . . : pondělí 11. května 2020 10:40:25
Default Gateway . . . . . . . . . : 192.168.0.1
DHCP Server . . . . . . . . . . . : 192.168.0.1

Or in the WiFi network card settings:

DHCP server na sitove karte

If you receive an IP address from the range 169.254.x.x (which is a Link-local address), I also recommend checking if the DHCP server is enabled on your WiFi router.

DHCP server

12. WiFi router firmware update

It can be downloaded from the WiFi router manufacturer’s website. Make sure the firmware is designed for your model and version of the WiFi router.

Example for TP-Link:

Problém s wifi routerem (how to fix wifi)

The model and version can also be read from below the WiFi router:

wifi problem

As an additional benefit, the firmware can add new features to the WiFi router. Personally, I have not had a bad experience with these updates..

13. Switch the WiFi router to factory settings

Another thing that can help is a restart to the default settings. This is done by holding down the reset button on the WiFi router for at least 20 seconds, sometimes half a minute.

Alternatively, this can be done directly via the web interface, see the image below:

Problém s wifi routerem (how to fix wifi)

14. Demand-side management (DSM) signal

I came across only an exceptional case when entire WiFi router crashed at certain times. It was later discovered that was caused due to the DSM signal (HDO signal in Czech). Simply put, it is the impulse from electrical substations that switches to the so-called higher and lower tariff. It is known to the general public as the switch to “cheap electricity”. I recommend that you find out the relevant switching times of your electricity distributor and monitor the behavior. Alternatively, look at the logs of the WiFi router. If the logs on the WiFi router are overwritten, select a lower Log level – e.g. Warning (value 4).

Example for TP-Link:

 

Problém s wifi routerem (how to fix wifi)

15. Replacing the old with the new one

If nothing really helps, it’s a good idea to consider buying a new WiFi router. Many households pay around 500 CZK a month for an internet connection, but when it comes to choosing a WiFi router, they try to save money. Due to cheap equipment, users are dissatisfied. Better invest a few hundred extra if you know the device has a better rating. Sometimes it’s nice to look at people’s reviews, for example at Amazon webpage.

wifi router

And what parameters to follow when choosing WiFi router?

  • Support for at least 802.11ac (or preferably the latest 802.11ax)
  • Number of antennas Today’s standard is two or more antennas – more antennas, helps the WiFi router to remove noise and increase signal quality
  • Antenna gain
  • Dual band signal – 2.4 and 5 GHz
  • Ports 1000 Mbps

TIP: Where not to place WiFi routers

c) Specific WiFi issues:

1) The WiFi station is still connecting and disconnecting to the Wi-Fi network:

This problem has been reported in practice with the Xiaomi 9 Lite mobile phone with MIUI version 10.3.4.0 (it will probably be all these models with the same MIUI version). It was enough to turn off IPv6 on the WiFi router (in practice, it turned out that the problem is probably caused by the RADVD service on the WiFi router).

2) The WiFi station does not connect to the original Wi-Fi network automatically after the laptop is wake up

If the notebook is connected to some Wi-Fi networks and it is hibernated, it may be disconnected from the original Wi-Fi network when it wakes up (and will not connect automatically). It can help to check Allow the computer to turn off this device to save power. However, this checkbox should be checked by automatically.

Note: The above behavior works the same when the notebook is running on a battery or to electricity.

The problem with a weak WiFi signal is solved in the article below:

How to increase WiFi signal [english]

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