Cisco router power-on/startup sequence

Cisco router power-on/startup sequence 1. Power-on self-check (POST) www.2cto.com 2. Load and run the boot guide microcode (stored in read-only memory ROM) 3. Search for IOS image files (stored in Flash) (1), Check Configuration registers (2), and parse configuration files in NVRAM (3) the default is to use the first file in Flash (4), try to start from the Network (5), RXBOOT (6), ROMMON4, loading IOS image files 5, looking for configuration files (stored in NVRAM) 6. Loading configuration files if there is no configuration file in NVRAM, enter Setup mode 7. The ROM function is running normally: stores the basic functions of the micro-code Bootstrap | POST ----> show versionMini IOS | ROM monitor (if the configuration file is corrupted, it can be started to the ROM monitor mode, similar to the Windows security mode, check the system) show running-config to view the RAM content co Nfigshow startup-config view NVRAM content config when the vro starts, execute a series of steps, called boot sequence (boot sequence), to test the hardware and load the required software. The startup sequence includes the following steps: 1. the router executes POST (POST upon startup ). POST checks the hardware to verify that all components of the device are currently operational. POST is stored in the ROM and runs from the ROM. 2. bootstrap finds and loads Cisco IOS software. Bootstrap is a program located in ROM used to execute the program. The bootstrap program is responsible for finding the location of each IOS program and then loading the file. By default, all Cisco routers load IOS software from flash memory. 3. Search for valid configuration files in NVRAM for IOS software. The following file is called startup-config. This file is generated only when the Administrator copies the running-config file to NVRAM. 4. If there is a startup-config file in NVRAM, The vro will load and run this file. Vro currently can operate. If no startup-config file exists in NVRAM, The vro starts setup mode to configure the preceding startup operations. ---------------------------------------------- To discuss the router startup sequence, Let's first look at the router's hardware composition: www.2cto.com 1. The router will POST after power-on first. Power On Self Test (the process of Self-check On the hardware) 2. After the POST is complete, read the BootStrap program in the ROM for preliminary guidance. 3. After the initial boot is complete, try to locate and read the complete IOS image file. Here, the router will first find the IOS file in FLASH. If the IOS file is found, read the IOS file and guide the router. 4. If the IOS file is not found in FLASH, the vro enters the BOOT mode and the IOS file on TFTP can be used in the BOOT mode. Or use TFTP/X-MODEM to send an IOS file to the FLASH drive of the vro (this process is generally called IOS filling ). After the transmission is complete, restart the vro to enable the CLI mode. 5. When the router initialization completes the IOS file, it starts to look up the STARTUP-CONFIG file in NVRAM, The STARTUP-CONFIG is called the startup configuration file. This file stores all the configurations and modifications we have made to the vro. After the vro finds the file, the vro loads all the configurations in the file and learns, generates, and maintains the route table according to the configuration, load all the configurations to RAM (the memory of the router), enter the user mode, and finally complete the startup process. Www.2cto.com 6. if there is no STARTUP-CONFIG file in NVRAM, the router will enter the query configuration mode, also known as the Q & A configuration mode, in this mode, all vro configurations can be configured in the form of Q &. However, we generally do not need this mode. We usually enter the CLI (Comman Line Interface) command Line mode, and then configure the router. OK. I believe that, as described above, you should have a new understanding of the router startup process?
We know that there is a software in the router called IOS, and IOS is called the Internet Operating System. It can be equivalent to the operating system of the router, just like XP, which we usually use. The router uses IOS to generate and maintain the route table. Similarly, as a router, there is also a part that functions the same as BIOS in our PC system, called MiniIOS. MiniIOS can make us in the FLASH Router does not exist in IOS, first boot up, enter the recovery mode, to use TFPF or X-MODEM to import IOS files to FLASH. Therefore, the router startup process should be as follows: