Definition - What does Router Firmware mean?
Router firmware is the preinstalled, embedded software that manages the control of routing protocols, administrative features and the router's security mechanism. Firmware is the most essential software in a router's read-only memory (ROM).
Techopedia explains Router Firmware
Firmware is primarily used to operate the router and works as an operating system by providing an interface, protocol configuration and security settings. It allows the router to be configured and customized according to the network operating environments.
Firmware cannot be deleted by a user; it can only be replaced by a newer version provided by the vendor.