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Cisco ME 3400 EthernetAccess Switch SoftwareConfiguration Guide
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Chapter3 Assigning the Switch IP Address and Default Gateway Modifying the Startup Configuration
To return to the default setting, use the no boot system global configuration command.
Controlling Environment Variables
With a normally operating switch, you enter the boot loader m ode onl y t hro ugh a sw itch c onso le
connection configured for 9600 bps. Unplug and then reconnect the switch power cord . After the switch
performs POST, the switch begins the autoboot process. The boot loader prompts the user for a break
key character during the boot-up sequence, as shown in t h is e xam ple :
***** The system will autoboot in 5 seconds *****
Send a break key to prevent autobooting.
The break key character is different for each operating system.
•On a SUN work station running UNIX, Ctrl-C is the break key.
•On a PC running Windows 2000, Ctrl-Break is the break key.
Cisco TAC has tabulated break keys for most common operating systems and provided an alternative
break key sequence for terminal emulators that do not support the break keys. To view this table, see:
http://www.cisco.com/warp/public/701/61.html#how-to
When you enter the break key, the boot loader switch: prompt appears.
The switch boot loader software provides support for nonvolatile environment variables, which can be
used to control how the boot loader, or any other software running on the system, behaves. Boot loader
environment variables are similar to environment variables that can be set on UNIX or DOS systems.
Environment variables that have values are stored in flash memory outside of the flash file system.
Each line in these files contains an environment variable name and an equal sign followed by the value
of the variable. A variable has no value if it is not listed in this file; it has a value if it is listed in the file
even if the value is a null string. A variable that is set to a null string (for example, “ ”) is a v a riable wit h
a value. Many environment variables are predefined and have default values.
Environment variables store two kinds of data:
•Data that controls code, which does not read the Cisco IOS configuration file. For exam ple, the name
of a boot loader helper file, which extends or patches the functionality of the boot loader can be
stored as an environment variable.
•Data that controls code, which is responsible for reading the Cisco IOS configuration file. For
example, the name of the Cisco IOS configuration file can be stor ed a s an e nvironment variabl e.
Step3 end Return to privileged EXEC mode.
Step4 show boot Verify your entries.
The boot system global command changes the setting of the BOOT
environment variable.
During the next boot cycle, the switch attempts to automatically boot the
system using information in the BOOT environment variable.
Step5 copy running-config startup-config (Optional) Save your entries in the configuration file.
Command Purpose