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Chapter 4
Assigning the Switch IP Address and Default Gateway
Environment variables store two kinds of data:
•
•
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.
For complete syntax and usage information for the boot loader commands and environment variables,
Note
refer to the command reference for this release.
Table 4-4
Table 4-4
Environment Variables
Variable
Boot Loader Command
BOOT
set BOOT filesystem:/file-url ...
A semicolon-separated list of executable files to
try to load and execute when automatically
booting. If the BOOT environment variable is not
set, the system attempts to load and execute the
first executable image it can find by using a
recursive, depth-first search through the flash file
system. If the BOOT variable is set but the
specified images cannot be loaded, the system
attempts to boot the first bootable file that it can
find in the flash file system.
MANUAL_BOOT
set MANUAL_BOOT yes
Decides whether the switch automatically or
manually boots.
Valid values are 1, yes, 0, and no. If it is set to no
or 0, the boot loader attempts to automatically
boot the system. If it is set to anything else, you
must manually boot the switch from the boot
loader mode.
CONFIG_BUFSIZE
set CONFIG_BUFSIZE size
Changes the buffer size that Cisco IOS uses to
hold a copy of the configuration file in memory.
The configuration file cannot be larger than the
buffer size allocation. The range is from 4096 to
524288 bytes.
78-16180-02
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.
describes the function of the most common environment variables.
Modifying the Startup Configuration
Cisco IOS Global Configuration Command
boot system filesystem:/file-url
Specifies the Cisco IOS image to load during the
next boot cycle. This command changes the
setting of the BOOT environment variable.
boot manual
Enables manually booting the switch during the
next boot cycle and changes the setting of the
MANUAL_BOOT environment variable.
The next time you reboot the system, the switch is
in boot loader mode. To boot the system, use the
boot flash:filesystem:/file-url boot loader
command, and specify the name of the bootable
image.
boot buffersize size
Specifies the size of the file system-simulated
NVRAM in flash memory. The buffer holds a
copy of the configuration file in memory. This
command changes the setting of the
CONFIG_BUFSIZE environment variable.
You must reload the switch by using the reload
privileged EXEC command for this command to
take effect.
Catalyst 3750 Switch Software Configuration Guide
4-15
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Troubleshooting
