What happen next in switch after boot up?

[nadeeemk]

When switch boots up what switch does the first thing? 

Please help me to understand this.

[Martin Carr]

Essentially there are 5 steps:

1. A 'POST' which is an acronym for 'Power on Self Test' is performed. Most computers do this (including a PC) this as the name suggests and performs hardware tests.

2. The switch loads the boot loader software.

3. The boot loader performs CPU initialization.

4. The boot loader initializes the flash file system.

5. The boot loader locates (and loads) the image into memory and control of the switch is then under IOS.

Martin

[omz]

The following details the router boot process:
1. The router is powered on.
2. The router first runs Power-On Self Test (POST)
3. The bootstrap checks the Configuration Register value to specify where to load the IOS. By default (the default value of Configuration Register is 2102, in hexadecimal), the router first looks for “boot system” commands in startup-config file. If it finds these commands, it will run boot system commands in order they appear in startup-config to locate the IOS. If not, the IOS image is loaded from Flash. If the IOS is not found in Flash, the bootstrap can try to load the IOS from TFTP server or from ROM (mini-IOS).
4. After the IOS is found, it is loaded into RAM.
5. The IOS attempts to load the configuration file (startup-config) from NVRAM to RAM. If the startup-config is not found in NVRAM, the IOS attempts to load a configuration file from TFTP. If no TFTP server responds, the router enters Setup Mode (Initial Configuration Mode).