© 2005 Cisco Systems, Inc. All rights reserved.INTRO v Managing Your Network Environment Managing Router Startup and Configuration

© 2005 Cisco Systems, Inc. All rights reserved.INTRO v Outline Overview Stages of the Router Power-On/Boot Sequence Internal Router Components How a Cisco Device Locates and Loads Cisco IOS Image and Configuration Files Configuration Register Summary

© 2005 Cisco Systems, Inc. All rights reserved.INTRO v Router Power-On Boot Sequence 1. Perform power-on self test (POST). 2. Load and run bootstrap code. 3. Find the Cisco IOS software. 4. Load the Cisco IOS software. 5. Find the configuration. 6. Load the configuration. 7. Run the configured Cisco IOS software.

© 2005 Cisco Systems, Inc. All rights reserved.INTRO v Router Internal Components

© 2005 Cisco Systems, Inc. All rights reserved.INTRO v ROM Functions Contains microcode for basic functions

© 2005 Cisco Systems, Inc. All rights reserved.INTRO v Finding the Cisco IOS Image

© 2005 Cisco Systems, Inc. All rights reserved.INTRO v Loading the Cisco IOS Image from Flash Memory The flash memory file is decompressed into RAM.

© 2005 Cisco Systems, Inc. All rights reserved.INTRO v Loading the Configuration Load and execute the configuration from NVRAM. If no configuration is present in NVRAM, enter setup mode.

© 2005 Cisco Systems, Inc. All rights reserved.INTRO v Determining the Current Configuration Register Value Configuration register value in show version command

© 2005 Cisco Systems, Inc. All rights reserved.INTRO v Configuration register bits 3, 2, 1, and 0 set boot option. Check the configuration register value with the show version command. Configuration Register Values

© 2005 Cisco Systems, Inc. All rights reserved.INTRO v show version Command

© 2005 Cisco Systems, Inc. All rights reserved.INTRO v show flash Command

© 2005 Cisco Systems, Inc. All rights reserved.INTRO v Displays the current and saved configuration show running-config and show startup-config Commands

© 2005 Cisco Systems, Inc. All rights reserved.INTRO v Summary When a router boots, it performs tests, finds and loads software, finds and loads configurations, and finally runs the software. The major internal components of a router include RAM, ROM, flash memory, NVRAM, and the configuration register. When a router boots, it searches for the Cisco IOS software image in a specific sequence: location specified in the configuration register, flash memory, a TFTP server, and ROM. The configuration register includes boot information specifying where to locate the Cisco IOS software image. The register can be examined with a show command and change the register value with the config-register global configuration command.

© 2005 Cisco Systems, Inc. All rights reserved.INTRO v