Tomato firmware enhances the capabilities of consumer rated routers. And unlike software applications that are installed onto your computers operating system, firmware is installed directly onto the flash memory chip. Tomato firmware can be uploaded directly through the admin interface or transferred using a TFTP software utility.
When you flash Tomato firmware to your router, some of the settings from the old firmware may remain. These old settings can cause conflicts and even make the router appear broken, when in fact, the router is perfectly fine. That is why it is so important to clear the flash memory before and after flashing Tomato firmware to your router.
Before you update your router with Tomato firmware, I recommend updating the factory firmware first. Factory firmware updates can take advantage of additional memory by updating the CFE. And depending on your router, you can upload 64k versions of Tomato firmware to routers (like the ASUS RT-N66U) that previously used only 32k of memory.