The following details the router boot process:
The router powers on. 3. The bootstrap checks the value of the configuration register to indicate where to load the IOS . By default (the configuration register’s default value is 2102 in hexadecimal), the router first looks for “boot system” commands in the startup-config.
The initial software that runs on a Cisco router is called bootstrap software and is usually stored in ROM. The bootstrap software is invoked when the router boots up. Flash – Flash memory resides on a processor board SIMM but can be expanded with (removable) PCMCIA cards.
The Power-On Self Test (POST) is a process that takes place on almost every computer during startup. This process is used to test the router hardware. When the router is powered on, the software on the ROM chip runs tests on multiple hardware components such as the CPU, RAM, and NVRAM.
The configuration file is missing from NVRAM. A router starts up and goes into setup mode. What is the reason for that? The IOS image is corrupt.
Start the router and interrupt the startup sequence by pressing Ctrl + Interrupt.
After an IP phone is powered, the following occurs: Power On Self-Test (POST): The phone performs a series of tests to ensure basic functionality. The phone will begin the boot process. The phone uses the Cisco Discovery Protocol to learn the voice VLAN. The phone initializes a simple IP stack.
Press pause on the terminal’s keyboard within 1 minute of powering it on to make the router switch to ROMmon. In confreg, type 0x2142 at rommon 1> Prompt to boot from Flash. type reset at rommon 2> prompt. Type no after each setup question or press Ctrl+C to bypass all questions.
The specific code in ROM that executes immediately after the power on step is part of a basic set of routines that form the framework for the Power On Self Test (POST) , which is the second defined step in the Computer startup sequence.
By default, all Cisco routers load IOS software from flash memory. Another possible location of the IOS image is a TFTP (Trivial File Transfer Protocol) server configured in a computer).