Cisco WS-C6506 Software Manual page 695

Chapter 23 Configuring Redundancy
If you hot insert a second supervisor engine, the second module communicates with the active supervisor
engine after completing its initial module-level diagnostics. Because the active supervisor engine is
already switching traffic on the backplane, no switching-bus diagnostics are run for the second
supervisor engine because running diagnostics can disrupt the normal traffic. The second supervisor
engine immediately enters standby mode. The active supervisor engine downloads the software image
and configuration to the standby supervisor engine, if necessary.
The supervisor engines use two flash images: the boot image and the run-time image. The boot image
filename, which is specified in the BOOT environment variable, is stored in NVRAM. The run-time
image is the boot image that the ROM monitor uses to boot the supervisor engine. After the system boots,
the run-time image resides in dynamic RAM (DRAM).
When you power up or reset a switch with the redundant supervisor engines, synchronization occurs to
ensure that the run-time and boot images on the standby supervisor engine are the same as the images
on the active supervisor engine.
The supervisor engines can have different run-time and boot images. If the boot image and the run-time
image are the same, and you change the BOOT environment variable or overwrite or destroy the current
boot image on the flash device that was used to boot the system, the run-time and boot images will differ.
Whenever you reconfigure the boot image, the active supervisor engine synchronizes its current boot
image with the standby supervisor engine.
The boot image is read directly into the flash file system. You can perform operations (such as copy,
delete, undelete, and so on) on the files that are stored on flash memory devices, and you can store the
boot image of the active supervisor engine in the standby supervisor engine bootflash. For more
information about using the flash file system, see
Supervisor Engine 1 and Supervisor Engine 2 have a Flash PC card (PCMCIA) slot (slot0) in addition
to the onboard flash memory; this slot can hold a Flash PC card that can store additional boot images.
The keywords for the slot are slot0: for linear flash devices and disk0: for ATA flash devices.
The term Flash PC card is used throughout this publication in place of the term PCMCIA card.
Note
Supervisor Engine 720 has two CompactFlash Type II slots. The CompactFlash Type II slots support the
CompactFlash Type II Flash PC cards. The keywords for the slots on the active Supervisor Engine 720
are disk0: and disk1:. The keywords for the slots on a redundant Supervisor Engine 720 are slavedisk0:
and slavedisk1:. Supervisor Engine 32 has one CompactFlash Type II slot. The CompactFlash Type II
slot supports the CompactFlash Type II Flash PC cards. The keyword for the slot on the active Supervisor
Engine 32 is disk0:. The keyword for the slot on a redundant Supervisor Engine 32 is slavedisk0:.
Because you can store multiple boot images, you must specify the name of the boot file image and the
location of the image file in the flash file system to boot and synchronize properly. For information about
how to specify the name and location of the boot image, see
Configuration."
In the synchronization process, the active supervisor engine checks the standby supervisor engine
run-time image to make sure that it matches its own run-time image. The active supervisor engine checks
three conditions:
If it needs to copy its boot image to the standby supervisor engine
•
If the standby supervisor engine bootstring needs to be changed
•
If the standby supervisor engine needs to be reset
•
The following section describes the conditions that can initiate the flash synchronization. For examples
of how the system synchronizes the supervisor engine flash images with various configurations, see the
"Supervisor Engine Synchronization Examples" section on page
OL-8978-04
Understanding How Supervisor Engine Redundancy Works
Chapter 26, "Working With the Flash File System."
Catalyst 6500 Series Switch Software Configuration Guide—Release 8.7
Chapter 25, "Modifying the Switch Boot
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