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Catalyst 6500 Series Switch Cisco IOS Software Configuration Guide—Release 12.1 E
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Chapter 4 Configuring EHSA Supervisor Engine Redundancy
Supervisor Engine Redundant Operation
EHSA standby mode provides the following features:
• Auto-startup and bootvar synchronization between active and redundant supervisor engines
• Hardware signals that detect and decide the active or redundant status of supervisor engines
• Clock synchronization every 60 seconds from the active to the redundant supervisor engine
• A redundant supervisor engine that is booted but not all subsystems are up: if the active supervisor
engine fails, the redundant supervisor engine becomes fully operational
• An operational supervisor engine present in place of the failed unit becomes the redundant
supervisor engine
Note The two Gigabit Ethernet interfaces on the redundant supervisor engine are always active.
When the switch is powered on, EHSA runs between the two supervisor engines. The supervisor engine
that boots first, either in slot 1 or 2, becomes the EHSA active supervisor engine. The Multilayer Switch
Feature Card (MSFC or MSFC2) and Policy Feature Card (PFC or PFC2) become fully operational. The
MSFC and PFC on the redundant supervisor engine come out of reset but are not operational.
The following events cause an EHSA switchover:
• Clock synchronization failure between supervisor engines
• MSFC or PFC failure on the active supervisor engine
In a switchover, the redundant supervisor engine becomes fully operational and the following occurs:
• All switching modules power up again
• Remaining subsystems on the MSFC (including Layer 2 and Layer 3 protocols) are brought up
• Access control lists (ACLs) are reprogrammed into supervisor engine hardware
Note In a switchover, there is a disruption of traffic because some address states are lost and then restored after
they are dynamically redetermined.
Supervisor Engine Redundancy Requirements
For redundant operation, the following requirements must be met:
• The active and redundant supervisor engines must be in slots 1 and 2.
• Each supervisor engine must have the resources to run the switch on its own, which means all
supervisor engine resources are duplicated. In other words, each supervisor engine has its own Flash
device and console port connections.
Note Make a separate console connection to each supervisor engine. Do not connect a “Y” cable
to the console ports.
• Both supervisor engines must have the same system image (see the “Copying Files to the Redundant
Supervisor Engine” section on page 4-4).