On an example I will use ASUS RT-G32 Rev.C1 router with firmware version 220.127.116.11.
First of all, let’s see if there is a firmware on the official website
In my case, the new version was 18.104.22.168.
Download the archive with the new firmware and unpack it.
Open the web-interface of the router by typing in the browser address http://192.168.0.1 and enter login – admin, password – admin, and look at the version of the firmware that is installed, usually it is written at the very top, for example “Firmware version: 22.214.171.124”.
Next you need to open the menu “Administration“, select a tab “Firmware Upgrade“, press “Browse” and select previously downloaded and unpacked from the archive firmware file, click “Send” and wait for the update process to complete.
The configuration of the router remains unchanged.
If there is a failure during the upgrade, the router can be restored using a utility that can be downloaded from the official site by clicking the link above.