5.5 Device Maintenance
ROM Monitor (ROMMON)
The ROM monitor area includes a low-level operating system that is normally used for manufacturing, testing, troubleshooting, and password recovery In ROM monitor mode, the router has no routing or IP capabilities.
Bootstrap Code
The bootstrap code is used to bring up the router during initialization It reads the configuration register to determine how to boot then, if instructed to do so, loads Cisco IOS Software
Boot Field Values
0x0 - Boot in ROM monitor 0x1 - Boot 1st flash image 0x2 - 0xF - Get image loading instruction from config in NVRAM
Password recovery
0x2146
Router Boot-up Process
1 - Run POST 2 - Run Bootstrap Code 3 - Locate CISCO IOS 4 - Load CISCO IOS 5 - Locate configuration (usually in NVRAM) 6 - Load configuration (put in running-config/RAM) 7 - Execute configuration
Configuration Register
16 bit value in hex, 0x2102(default) Force the router to boot into the ROM monitor Select a boot source and default boot filename Control broadcast addresses Recover a lost password Change the console line speed
CISCO IOS Recovery options
Can store backup files in: SCP, FTP, TFTP, and MD5 verify
POST
Power On Self-Test
Boot Options
ROMMON 1st IOS image in flash Get image loading instructions from config in NVRAM Controlled by routers configuration register.