Cisco Catalyst 2960 Series, Configuration Manual

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The switch broadcasts TFTP server requests if the TFTP server is not obtained from the DHCP replies,
if all attempts to read the configuration file through unicast transmissions fail, or if the TFTP server name
cannot be resolved to an IP address. Note
How to Control Environment Variables
With a normally operating switch, you enter the boot loader mode only through the console connection. Unplug
the switch power cord, then reconnect the power cord. Hold down the
MODE
button until you see the boot
loader switch prompt
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, functions. 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 present; it has a value if it is listed even if the value is a null string.
A variable that is set to a null string (for example,
“ ”
) is a variable with 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 example, 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 stored as an environment variable.
You can change the settings of the environment variables by accessing the boot loader or by using Cisco IOS
commands. Under normal circumstances, it is not necessary to alter the setting of the environment variables.
Common Environment Variables
This table describes the function of the most common environment variables.
Consolidated Platform Configuration Guide, Cisco IOS Release 15.2(4)E (Catalyst 2960-X Switches)
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Information About Performing Switch Setup Configuration