1 © 2002, Cisco Systems, Inc. All rights reserved. Router boot procedure

222 © 2002, Cisco Systems, Inc. All rights reserved. Understanding the router memory Router contains  RAM  ROM  NVRAM  FLASH (EEPROM) Data also stored on TFTP server

333 © 2002, Cisco Systems, Inc. All rights reserved. Graphic from CISCO notes

444 © 2002, Cisco Systems, Inc. All rights reserved. Router start-up RAM BOOTSTRAP BASIC IOS ROM Start up configuration NVRAMFLASH Current IOS Configuration register IOS & Configuration TFTP Server IOS and running-configuration needed in RAM for working router

555 © 2002, Cisco Systems, Inc. All rights reserved. Router start-up Router# show flash  looks at IOS image in flash Router# show startup-config  looks at configuration file in NVRAM Router# show version  looks at IOS image RAM and configuration register  o? from ROM monitor mode

666 © 2002, Cisco Systems, Inc. All rights reserved. Router Bootstrap BOOTSTRAP looks at configuration register depending on value of least significant 4 bits 0 uses ROM monitor mode RAM BOOTSTRAP BASIC IOS ROM Start up configuration NVRAMFLASH Current IOS Configuration register IOS & Configuration TFTP Server 1 uses Basic IOS from ROM 2- F look in NVRAM for boot system settings IOS

777 © 2002, Cisco Systems, Inc. All rights reserved. Router default sequence Router# configure terminal Router(config)# boot system flash Router(config)# boot system tftp Router(config)# boot system ROM order of entry specifies order of fall-back sequence Router # show running-config or show startup- config (if saved) shows the boot sequence NOTE This requires a pre-emptive look into the startup configuration file

888 © 2002, Cisco Systems, Inc. All rights reserved. Router default sequence RAM BOOTSTRAP BASIC IOS ROM Start up configuration NVRAMFLASH Current IOS Configuration register IOS & Configuration TFTP Server What happens if boot system commands fail ? Default search sequence is used FLASH, TFTP, ROM

999 © 2002, Cisco Systems, Inc. All rights reserved. Router default sequence RAM BOOTSTRAP BASIC IOS ROM Start up configuration NVRAMFLASH Current IOS Configuration register IOS & Configuration TFTP Server Default sequence FLASH - TFTP - ROM IOS

10 © 2002, Cisco Systems, Inc. All rights reserved. Configuration file next RAM BOOTSTRAP BASIC IOS ROM Start up configuration NVRAMFLASH Current IOS Configuration register IOS & Configuration TFTP Server IOS has been loaded - Configuration File Next IOS IOS looks at configuration register Is ‘Ignore Configuration’ disabled ? YES - load configuration file from NVRAM Running configuration

11 © 2002, Cisco Systems, Inc. All rights reserved. Configuration file next RAM BOOTSTRAP BASIC IOS ROM Start up configuration NVRAMFLASH Current IOS Configuration register IOS & Configuration TFTP Server IOS has been loaded - Configuration File Next IOS IOS looks at configuration register Is ‘Ignore Configuration’ enabled ? YES - enter set-up mode

12 © 2002, Cisco Systems, Inc. All rights reserved. Setup mode Guided set of questions with defaults for basic router configuration Can be invoked with the setup command Can be bypassed (select [n] at first option or CTRL -C)  Router then enters un-configured state Several options then exist to configure the router  Manually using configure terminal  Use a file from tftp server  Use a file from PC running hyper-terminal Text configuration file are generated by  copy running-config tftp  show running-config (then start hyper-terminal capture mode)

13 © 2002, Cisco Systems, Inc. All rights reserved. Configuration file loaded RAM BOOTSTRAP BASIC IOS ROM Start up configuration NVRAMFLASH Current IOS Configuration register IOS & Configuration TFTP Server IOS Running configuration Manual Configuration Text file from PC with hyperterminal