Switch Boot Sequence- A Switch with Intial Settings
Switches interconnect devices. Unlike a router, which must be initially configured to be operational in a network, switches can be deployed out of the box without initially being configured. However, for
management and security reasons, switches should always be manually configured to better meet the needs of the network.
Here you will learn how to configure initial settings on a Cisco switch.
Switch Boot Sequence:
Before you can configure a switch, you need to turn it on and allow it to go through the five-step boot sequence. After a Cisco switch is powered on, it goes through the following five-step boot sequence:
Step 1.
The switch loads a power-on self-test (POST) program stored in read-only memory (ROM).
POST checks the central processing unit (CPU) subsystem. It tests the CPU, dynamic random-
access memory (DRAM), and the portion of the flash device that makes up the flash file system.
Step 2.
The switch loads the boot loader software. The boot loader is a small program stored in ROM
that is run immediately after POST successfully completes.
Step 3.
The boot loader performs low-level CPU initialization. It initializes the CPU registers, which control where physical memory is mapped, the quantity of memory, and its speed.
Step 4.
The boot loader initializes the flash file system on the system board.
Step 5.
Finally, the boot loader locates and loads a default IOS operating system software image into
memory and gives control of the switch over to the IOS.
The boot system Command:
The switch attempts to automatically boot by using information in the BOOT environment variable. If this variable is not set, the switch attempts to load and execute the first executable file it can find. On Catalyst 2960 Series switches, the image file is normally contained in a directory that has the same name as the image file (excluding the .bin file extension). The IOS operating system then initializes the interfaces using the Cisco IOS commands found in the startup- config file. The startup-config file is called config.text and is located in flash.
The BOOT environment variable is set using the boot system global configuration mode command.
Notice that the IOS is located in a distinct folder and the folder path is specified. Use the command
show boot to see what the current IOS boot file is set to.
Command:
SW-A(config)# boot system flash. /c2960-lanbasek9-mz.150-2.SE/ c2960-lanbasek9-mz.150-2.SE.bin
Command Break-down:
boot system >>>>>>>>>>>>>>>>>>>>The main command
flash. >>>>>>>>>>>>>>>>>>>>>>>>>The storage device
c2960-lanbasek9-mz.150-2.SE/ >>>>>The path to the file system
c2960-lanbasek9-mz.150- 2.SE.bin >>The IOS file name
Source: CCNAv7: Switching, Routing, and Wireless Essentials Companion Guide:
