|  | 5.1 | Router Boot Sequence and Setup Mode
| 5.1.2 | Router startup sequence
After the power-on self test on the router, the following events occur as the router initializes: Step 1 -- The generic bootstrap loader, in ROM, executes on the CPU card. A bootstrap is a simple, preset operation to load instructions that in turn cause other instructions to be loaded into memory, or cause entry into other configuration modes. Step 2 -- The operating system (Cisco IOS) can be found in one of several places. The location is disclosed in the boot field of the configuration register. If the boot field indicates a Flash, or network load, boot system commands in the configuration file indicate the exact location of the image. Step 3 -- The operating system image is loaded. Then, when it is loaded and operational, the operating system locates the hardware and software components and lists the results on the console terminal. Step 4 -- The configuration file saved in NVRAM is loaded into main memory and executed one line at a time. These configuration commands start routing processes, supply addresses for interfaces, set media characteristics, and so on. Step 5 -- If no valid configuration file exists in NVRAM, the operating system executes a question-driven initial configuration routine referred to as the system configuration dialog, also called the setup dialog. Setup is not intended as the mode for entering complex protocol features in the router. You should use setup to bring up a minimal configuration, then use various configuration-mode commands, rather than setup, for most router configuration tasks.