Cisco boot process simple router is divided into three parts
1. Check the hardware
2. Run IOS
3. import the configuration file.
To understand Cisco start-up process of the router must first look at Cisco's main storage hardware routers and their role.
ROM read-only memory is used to maintain a hardware router which stores the bootstrap program and the POST program Mini IOS. Flash which is used to store the router IOS image complete hardware. Cisco router IOS is equivalent to the operating system is not damaged IOS IOS image or the router will not work.
NVRAM startup configuration file is used to store the Startup-config router hardware. The last time before the router starts saved configuration is stored here.
When RAM stores the router starts from IOS after Running-config-extracting file copy operation by the configuration and startup configuration file to learn Routing-table routing table and packet queue.
Then learn more about the boot process of Cisco routers
a run after the first router powered POST program in the ROM Power On Self Test to detect the router hardware commonly known as POST.
Two, followed by the detection of the start mode is determined, and the register value register boot program executed in the bootstrap ROM. Format register value for the state column 0x21YZ Y
0x210Z loading a configuration file from nvram
0x214Z not load the configuration file from nvram
Z state from start column 0x21Y0 CtrlBreak0x21Y1 rommon press when the prompt is started from mini ios router starts the prompt is Routerboot0x21Y, starting two register values, we often use the prompt is Router from flash 0x2102 0x2142 not properly read the saved configuration.
Third, if the normal boot program to start the press find Flash IOS image. Start properly if found IOS image is read. If you do not find the IOS image into the boot mode that is Mini IOS start. boot mode under IOS may be used on a TFTP or TFTP / X-modem as a router Reprime IOS. If the Mini IOS also failed to start then enter the rom monitor mode. Fourth, after reading the IOS and boot program will be more successful initialization register value determines the load or do not load the startup configuration file. If you choose to load the startup configuration file in NVRAM find and loaded into RAM to become the running configuration file. If you choose not to load or no startup configuration file, the router will be asked to enter configuration mode in question-and basic configuration of the router. Fifth, enter user mode process is completed. Cisco Router Overview The router startup process is special purpose computer. Because it is also a computer so the boot process. When you start the router will have some information and sent from the console port. If you have to connect the PC to the console port will then display all the information in the Super start a terminal window. Information includes the size of a loaded version of the IOS IOStm1721 softwareXXX-X-XVersionXXXXX XX2 ports quantity 2 Ethernet / IEEE 802.3 interfaces and three types of interfaces 4NVRAM size of 125K bytes of non-volatile configuration memory5 flash. 32768K bytes of processor board system flash through the router backplane LED lampSome indication can be obtained.
Note:
IOS is stored in flash memory
Boot program stored in the ROM
Startup configuration file stored in NVRAM.