Cisco router Startup Process

Cisco router Startup Process
The Startup Process of a Cisco router is divided into four main stages: 1. execute POST 2. load the bootstrap program 3. search for and load Cisco IOS software 4. find and load the startup configuration file, or enter the setup Mode 1. executing POST power-on self-check (POST) is a process that is essential for starting each computer. The POST process is used to detect the router hardware. When the router is powered on, the software on the ROM chip will execute POST. In this self-check process, the router executes Diagnostics through ROM, mainly for several hardware components including CPU, RAM, and NVRAM. After the POST is complete, the router runs the bootstrap program. 2. After the bootstrap program POST is loaded, the bootstrap program will be copied from ROM to RAM. After entering RAM, the CPU executes the commands in the bootstrap program. The main task of the bootstrap program is to find Cisco IOS and load it to RAM. Note: If you connect to the vro console, the output content is displayed on the screen. 3. Search for and load Cisco IOS to search for Cisco IOS software. IOS is usually stored in flash memory, but may also be stored in other locations, such as TFTP (simple File Transfer Protocol) servers. If the complete IOS image cannot be found, the lite version of IOS will be copied from ROM to RAM. This version of IOS is generally used to help diagnose problems, or to load the full version of IOS to RAM. Note: The TFTP server is usually used as the backup server for IOS, but can also serve as the central point for storing and loading IOS. Some earlier Cisco routers can run IOS directly from flash memory, but today's routers will copy IOS to RAM for CPU execution. Note: Once IOS starts loading, you may see a string of BITs (#) during image decompression (#). 4. Search for and load the configuration file to find the startup configuration file. After IOS is loaded, the bootstrap program searches for the startup configuration file (also known as startup-config) in NVRAM ). This file contains the previously saved configuration commands and parameters, including: 1. interface address 2. route information 3. password 4. if the startup configuration file startup-config is in NVRAM, other configurations saved by the network administrator will be copied to RAM as the running configuration file running-config. Note: If the startup configuration file does not exist in NVRAM, The vro may search for the TFTP server. If the vro detects that an active link is connected to the configured vro, a broadcast is sent through the active link to search for the configuration file. This will cause the router to pause, but you will eventually see the following console message: <routerpauses here while it broadcasts for a configuration file within SS an activelink> % Erroropening t ftp://255.255.255.255/network-confg (Timed out) % Erroropening t ftp://255.255.255.255/cisconet.cfg (Timed out) executes the configuration file. If the startup configuration file is found in NVRAM, IOS loads it to RAM as running-config and executes the commands in the file in one row. The running-config file contains the interface address, and can start the routing process and configure the vro password and other features. Enter the Setting Mode (optional ). If the startup configuration file cannot be found, the router will prompt you to enter the setup mode. The setting mode contains a series of problems, prompting you to enter some basic configuration information. The setting mode is not suitable for complex router configurations. network administrators generally do not use this mode. When you start a router that does not contain the startup configuration file, you will see the following problem after loading the IOS: Wouldyou like to enter the initial configuration dialog? [Yes/no]: no this course does not use the configuration mode to configure the router. When prompted to enter the set mode, always answer no. If you answer yes and enter the setting mode, you can press Ctrl-C to terminate the setting process at any time. If the setting mode is not used, IOS creates the default running-config. The default running-config is the basic configuration file, including the router interface, management interface, and specific default information. The default running-config does not contain any interface address, route information, password, or other specific configuration information. The command line interface may ask the following question before a prompt is displayed based on the platform and IOS: Wouldyou like to terminate autoinstall? [Yes]: <Enter> Pressthe Enter key to accept the default answer. router> Note: If the startup configuration file is found, running-config may also contain the host name. The prompt displays the Host Name of the Router. Once the prompt is displayed, the router starts to run IOS with the current running configuration file. The network administrator can also start to use the IOS command on the vro.