What is the first step a router takes to find a bootable IOS?

The first step a router takes to find a bootable IOS is to check the configuration register setting. The configuration register is a critical setting stored in the router's non-volatile RAM (NVRAM) that defines how the router behaves during the boot process. It determines the source from which the router will attempt to load its operating system.

If the configuration register is set to a value that specifies loading the IOS from flash memory, the router will subsequently look for the IOS image in flash or follow any other directives specified by the configuration register. This process is essential because it establishes the boot mode and allows the router to recognize where to search for the operating system, ensuring that it attempts to load the correct file based on the settings defined within the configuration register.

Understanding this step is crucial for effective troubleshooting and configuration of Cisco routers, as it lays the groundwork for how subsequent loading actions will occur based on the set parameters.