Please go through the following steps to understand the router boot sequence:
- The POST is performed; it will test the hardware to verify that all the components of the device are working and present. The POST checks for the different interfaces that exist. As we know already, POST exists in ROM:
Main phases of the router boot sequence
- Bootstrap will then search for and load the Cisco IOS. Bootstrap is a program in ROM that is used to execute programs. It is responsible for finding where each IOS program is located and then loading the file. As said previously, the IOS by default is stored in flash in all Cisco routers, but only after the configuration register is read and NVRAM is checked for the boot sequence.
- After the IOS is decompressed into RAM, the IOS looks for a valid configuration file in NVRAM.
- If a startup configuration file is...
