|  | 5.1 | Router Boot Sequence and Setup Mode
| 5.1.1 | Router startup routine
A router initializes by loading the bootstrap, the operating system, and a configuration file. If the router cannot find a configuration file, then it enters setup mode. The router stores, in NVRAM, a backup copy of the new configuration from setup mode. The goal of the startup routines for Cisco IOS software is to start the router operations. The router must deliver reliable performance in its job of connecting the user networks it was configured to serve. To do this, the startup routines must: Make sure that the router comes up with all its hardware tested. Find and load the Cisco IOS software that the router uses for its operating system. Find and apply the configuration statements about the router, including protocol functions and interface addresses. When a Cisco router powers up, it performs a power-on self test (POST). During this self test, the router executes diagnostics from ROM on all hardware modules. These diagnostics verify the basic operation of the CPU, memory, and network interface ports. After verifying the hardware functions, the router proceeds with software initialization.