CCNA 5.3 Managing Configuration Register
- All Cisco routers have a 16-bit software register (Configuration) in NVRAM
- Configuration register loads IOS from flash memory and startup-config file from NVRAM
- Default configuration setting on Cisco router is 0x2102
- 0x means that the digits that follow are in hexadecimal
- Software configuration meaning:
- Show version command can be used to check current value of configuration register
- Configuration register value can be changed to modify how the router boots and runs
- Config-register command can be used to change config register value
- To recover a router password, user have to turn on bit 6 (0x2142) of configuration register to ignore the NVRAM contents (start-up config)
- Ctrl +Break key is used to interrupt boot sequence and enter ROM monitor mode
- I command is used to reset the router
- boot system command allows user to tell router which file to boot from flash memory
- Cisco's suggested IOS backup routine: flash, TFTP host, ROM
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