Interpreting the Startup Process of a CISCO Router

On CISCO routers, there are ROM, NVRAM, RAM, and Flash. the four storage media have different functions. IOS is loaded in FLASH. RAM stores the current running configuration file (running-config) of the router, and the current startup configuration file (startup-config) of the router) it is stored in NVRAM, And the mini iOS, BootStrap, and RomMonitor running mode programs are loaded in the ROM.

In fact, the physical architecture of a ROUTER is similar to that of a PC in daily life. The PC motherboard, memory, processor, and so on all exist in the route. a pc is not made into a ROUTER, for example, a large number of foreign ROUTEROS, domestic sea spider, and other soft routing systems are used.

(1) The POST self-check process is performed after the router is powered on and started.

(2) After the POST self-check is passed, it will be guided through the BootStrap program in the ROM inside the router. After completing the initial boot, you will find the complete IOS network operating system in FLASH. If you find the complete Ios file in the Rom, load the boot.

(3) If the complete IOS file is not found in Fash, you can change the hexadecimal value of the Register to another mode, such as the MiniIos or RomMonitor mode. Upload a complete Ios file through the TFTP service, restart the router, and then enter the configuration in the normal mode of the route.

(4) When the Ios file is fully loaded, it will find the existence of the Startup configuration file Startup-config of the vro in NVRAM, this configuration file stores the configuration entry information that has been saved by the vro, but the Running-Config file in the next process. Load all the configurations of the vro, copy the file to Ram, and then start to enter the user configuration mode for related routing configuration. If the start configuration file (startup-config) is not found in NVRAM, it will enter a wizard-type configuration mode for router configuration. You can select N to go To the CLI configuration page.