Normally, you can update a router's firmware through the console by accessing the router like you would a website, like through a URL such as http://192.168.1.1. However, that doesn't always work.
If the console doesn't load because your router is bricked or is failing in some other way, the alternate method is to use a TFTP utility like the one provided by Linksys.
While it's true that there are TFTP command-line utilities built-in to most operating systems, the client Linksys provides might be easier to use since it provides a graphical interface (i.e. there are buttons and text boxes).
The Linksys TFTP client offers similar functionality to the command line. Through their utility, you specify the location of the firmware BIN file, the router's administrative password, and its IP address. The client displays status and error messages as would appear on the command line, and the client even works with other TFTP capable routers apart from Linksys ones.
How to Upgrade a Linksys Router Using TFTP
The download page where Linksys used to provide their TFTP client has been reported down for a long time, but you can still grab the download from Archive.org's Wayback Machine.
Visit the above link and then download the utility mentioned on that page. The file will download as Tftp.exe.
Open the file to see an Upgrade Firmware screen with a few text boxes.
In the first box, enter the router's IP address.
Make sure to find what IP address the router is using.
In the Password field, write whatever it is that you chose as your router's password.
If you have never changed the router's password, then you can use the default password that was shipped with your Linksys router.
In the final box, click the three little dots to browse for the firmware file.
Click or tap Upgrade to apply the firmware.
It's of utmost importance to not shut down your computer or unplug the router during this process. Any disturbance might further damage the software and make it even harder to gain access to the router's administrative console.
If the firmware is applied successfully, you should be able to log in using the web-based method mentioned above.
If you run into errors that prevent the firmware from applying, shut down the router, unplug it for 30 seconds, and then repeat the process from Step 1.
If the upgrade process isn't producing the desired result for you, it might be time to look at purchasing a new router.The 10 Best Linksys Routers of 2021