Router Boot Sequence is something I studied for my CCNA exam back in August, but I've forgotten the details of the process with time. I had a discussion with my supervisor today about what exactly is the startup process of a computer and it made me realize that I need to brush up on the topic. So I consulted the Todd Lammle book that I used for my CCNA. Here is the summary of the default boot sequence:
- Power-on self-test checks the hardware to verify if all components of the device are operational and if necessary components are present. Stored in and run from ROM.
- Bootstrap, located in ROM, then looks for Cisco IOS. It checks in this particular order- the Flash memory, TFTP Server and the ROM. The operating system, once found, is loaded in the RAM.
- Next step is to find the startup-config file. It's in NVRAM by default. If found, it is copied over to the RAM and loaded there. The router is ready to be used at this point. But in case that the router is missing startup-config file, it is searched for at a TFTP server. If that fails too, the router starts in the setup mode (which I've personally never bothered to look at by the way. I just skip it).
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| Default Router Boot Sequence |
So there you have it, the default boot sequence of Cisco routers. My next post will be on EIGRP.
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