Resetting to factory defaults will clear your Router's custom settings and bring them to a new condition. This is an important step in resolving some network problems. Resetting to factory settings is relatively easy, but every router is slightly different.
What is a factory reset and when should you do it?
Resetting is not the same as restarting, sometimes mistakenly referenced Similar to a PC, a reboot shuts down your router and restarts it. This is a good troubleshooting step if your router reacts strangely.
Resetting to factory defaults clears all your data from the router. This includes all passwords, Wi-Fi network details (such as your network name (SSID) and passphrase) and any other settings that you have changed.
Basically, you bought the router only from the factory, hence the name. And that's the point. If your router behaves strangely and did not help restart ̵
Resetting to factory settings is a good idea if you sell or dispose of your router. This will allow anyone who next receives your router to reboot without seeing your personal information (such as your Wi-Fi passphrase).
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How to Reset a Router to Factory Defaults with a Button
Warning : As explained above deletes all your router's custom settings, including the Wi-Fi network passphrase! You have to set it up again.
Virtually every router uses a different administration interface, but that's fine. You may be able to completely bypass it. First, have a look at the router – most of them have a reset button on the back or the bottom. You may need an unfolded paperclip to press on.
If you press and hold the button for 10 seconds on many routers, the router will be reset at the factory. If this does not work, try the 30-30-30 method:
- Press and hold for 30 seconds.
- Disconnect the power plug for 30 seconds.
- Reconnect the router.
- Hold down the reset button for another 30 seconds.
How to Reset a Router to Factory Default Settings via the Web Interface
If your router does not have a reset button, you must reset it using an option in the configuration interface.  We recommend that you consult the manual of your router. You can search the Internet for the model name of your router and enter "manual" to find an online version. The guide will help you connect to the web interface of your router and also tell you where the reset option is.
Unless you have a mesh Wi-Fi system (in which case, you must use the device's app to reset). Usually, you first determine the IP address that you need to log in to the administrator interface of your router.
For Windows 10, see this information under Settings> Network and Internet. Then click on "Show Network Properties" for the entry "Default Gateway" – this is the IP address. How to find the IP address of your router on each platform.
Type this IP address in the address bar of your favorite web browser and press Enter. You should see the administrator interface of your router and a prompt to enter the username and password. If you have never changed the credentials of your router, the username and password is probably "admin" (without quotation marks). If you are not sure, look for your model on a website like routerpasswords.com. You will also find this information in the manual of your router.
Here you can search for options to reset to factory settings. They are different for each router manufacturer (and may vary from model to model). Review the Restore, System, or Settings tabs.
On the Asus router, the Factory Default option is called Administration> Restore / Save / Upload. 
You may also be able to save the settings of your router to a file via its web interface. After resetting the router to factory settings, import this file again. However, if these settings cause a problem, restoring the saved settings file may also recover the error.
Resetting the router erases everything you've done to customize, from Wi-Fi passphrases to your custom DNS server. Essentially, they have a fresh-out-of-the-box router again.