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Catalyst 6500 Series Switch Software Configuration Guide—Release 8.7
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Chapter 23 Configuring Redundancy
Understanding How Supervisor Engine Redundancy Works
Understanding How Supervisor Engine Redundancy Works
Note
The redundant supervisor engines must be of the same type with the same model feature card. The
WS-X6K-SUP1-2GE and the WS-X6K-SUP1A-2GE (both without PFCs) are compatible for redundancy.
For supervisor engines with PFCs, the PFCs must be identical for redundancy (two PFCs, two PFC2s, two
PFC3As, two PFC3Bs, or two PFC3BXLs).
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 Trunking 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.
For Supervisor Engine 1 and Supervisor Engine 2, you must install the redundant supervisor engines in
slots 1 and 2 of the chassis. The Supervisor Engine 720 and Supervisor Engine 32 slot requirements are
as follows: With a 3-slot chassis, install Supervisor Engine 720 and Supervisor Engine 32 in either slot 1
or 2. With a 6-slot or a 9-slot chassis, install Supervisor Engine 720 and Supervisor Engine 32 in either
slot 5 or 6. With a 13-slot chassis, install Supervisor Engine 720 and Supervisor Engine 32 in either slot 7
or 8. You must install redundant supervisor engines in both slots.
The redundant supervisor engines are hot swappable. The system continues to operate with the same
configuration after switching over to the redundant supervisor engine.
Note
To allow you to control the booting of each supervisor engine separately, the configuration registers are
not synchronized between the supervisor engines.
Note
The switchover time from the active supervisor engine to the standby supervisor engine does not include
the spanning-tree convergence time.
At power-up, both supervisor engines run initial module-level diagnostics. Assuming that both
supervisor engines pass this level of diagnostics, the two supervisor engines communicate over the
backplane, allowing them to cooperate during the 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.
Note
The terms
slot 1
and
slot 2
refer to the redundant supervisor engines. As noted earlier, Supervisor
Engine 720 and Supervisor Engine 32 have different slot requirements.
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.
