SROS BOOT UP PROCESS

Similar to other networking system examinations, the Nokia IP Networking Fundamentals Exam thoroughly examines the boot-up process. This process is a frequent subject of questions. Understanding the boot-up process is vital as it assists in recovering devices stuck in a cyclic loop or when they are bricked, among other issues. I have had to recover numerous devices myself, which often become bricked due to human or configuration errors. This is typically the same process for any device running the SROS platform. SROS stands for Service Router Operating system.

BOBO-tim-co

BOBO-TIM-CO

The topic is not a typo; it's an acronym I devised to memorize the boot process of the Nokia 7750 and other devices running SROS. Here's what the acronym represents:

1) BO - Boot.ldr

2) BO - Bof.cfg

3) TIM - TiMOS file

4) CO - Config.cfg

Boot.ldr

This is the initial file that is called upon during the boot-up process. It contains the system's bootstrap image. Once this has loaded successfully, it initiates the next file, the bof.cfg.

Bof.cfg

The bof.cfg file holds instructions for the locations of configuration files, image files, and the management IP. BOF stands for Boot Option File. It also encompasses auto-discovery instructions, among other directives. Key points to remember for the exam include:

1) The image file location is detailed within the bof.cfg and is the first item to load. Locations for backup images, if configured, are also specified here. Without inclusion in the bof.cfg, an image file will not load. The naming convention for image files is TiMOS-xR.y, where 'x' represents the version and 'y' the release number. For instance, TiMOS-3.4R2 denotes version 3.4, release 2.

2) Following the image files, the bof.cfg loads the configuration files. You can specify primary, secondary, and even tertiary configuration files. Additionally, console parameters are set within the bof, and CLI lines are available for configuring management, often used for out-of-band management systems.

7750 storage SySTEm

CF1, CF2, CF3

The 7750 features three storage systems: CF1, CF2, and CF3, all of which can house files and configurations. CF3, a removable compact flash memory card, is often essential for booting the device as it searches for boot.ldr, bof.cfg, and timos on CF3. It is advisable to save the bof file to CF3, as well as CF1 and CF2. If feasible, include copies of the timos and cfg files in the other storage areas. This ensures that, in the event of recovery, the bof file can be altered to point to an alternate storage zone, allowing the system to load. Additionally, CF3 can be transferred to another 7750 unit—similar to its original position—and the system will boot from the new unit, mirroring the original setup. This method offers a swift solution for replacing faulty units, particularly if the issue originates from the backplane.