Understanding How Supervisor Engine Redundancy Works - Cisco WS-X6066-SLB-APC - Content Switching Module Software Manual

Understanding How Supervisor Engine Redundancy Works

Understanding How Supervisor Engine Redundancy Works
Redundant supervisor engines must be of the same type with the same model feature card.
Note
When you install two supervisor engines, the first supervisor engine to come online becomes the active
module; the second supervisor engine goes into standby mode. All administrative and network
management functions, such as SNMP, command-line interface (CLI) console, Telnet, Spanning Tree
Protocol (STP), Cisco Discovery Protocol (CDP), and VLAN Trunk Protocol (VTP) are processed on
the active supervisor engine.
On the standby supervisor engine, the console port is inactive, the module status shows as "standby," and
the status for the uplink ports is shown normally.
You must install redundant supervisor engines in slots 1 and 2 of the chassis. Redundant supervisor
engines are hot swappable. The system continues to operate with the same configuration after switching
over to the redundant supervisor engine.
To allow you to control the booting of each supervisor engine separately, the configuration registers
Note
are not synchronized between the supervisor engines.
The switchover time from the active to the standby supervisor engine does not include spanning tree
Note
convergence time.
At power-up, both supervisor engines run initial module-level diagnostics. Assuming both supervisor
engines pass this level of diagnostics, the two supervisor engines communicate over the backplane,
allowing them to cooperate during switching-bus diagnostics. The supervisor engine in slot 1 becomes
active, and the supervisor engine in slot 2 enters standby mode. If the software versions of the two
supervisor engines are different, or if the NVRAM configuration of the two supervisor engines is
different, the active supervisor engine automatically downloads its software image and configuration to
the standby supervisor engine.
If the background diagnostics on the active supervisor engine detect a major problem or an exception
occurs, the active supervisor engine resets. The standby supervisor engine detects that the active
supervisor engine is no longer running and becomes active. The standby supervisor engine can detect if
the active supervisor engine is not functioning and can force a reset, if necessary. If the reset supervisor
engine comes online again, it enters standby mode.
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 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 runtime image. The boot image
filename is specified in the BOOT environment variable, which is stored in NVRAM. The runtime image
is the boot image that the ROM monitor uses to boot the supervisor engine. After the system boots, the
runtime image resides in dynamic RAM (DRAM).
When you power up or reset a switch with redundant supervisor engines, synchronization occurs to
ensure that the runtime and boot images on the standby supervisor engine are the same as the images on
the active supervisor engine.
Catalyst 6000 Family Software Configuration Guide—Releases 6.3 and 6.4
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Chapter 22 Configuring Redundancy
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