Cisco Catalyst 6500 Series User Manual

15-13
Catalyst 6500 Series Switch and Cisco 7600 Series Router Firewall Services Module Configuration Guide
OL-6392-01
Chapter 15 Using Failover
Understanding Failover
Failover Monitoring
The FWSM monitors each module for overall health and for interface health. See the following sections
for more information about how the FWSM performs tests to determine the state of each module:
• Module Health Monitoring, page 15-13
• Interface Monitoring, page 15-14
Module Health Monitoring
The FWSM determines the health of the other module by monitoring the failover link. When a module
does not receive hello messages on the failover link, then the module sends an ARP request on all
interfaces, including the failover interface. The FWSM retries a user-configurable number of times. The
action the FWSM takes depends on the response from the other module. See the following possible
actions:
• If the FWSM receives a response on any interface, then it does not fail over.
• If the FWSM does not receive a response on any interface, then the standby module switches to
active mode and classifies the other module as failed.
Failover link failed during
operation
No failover Mark failover
interface as failed
Mark failover
interface as failed
You should restore the failover
link as soon as possible because
the module cannot fail over to the
standby module while the failover
link is down.
Failover link failed at startup No failover Mark failover
interface as failed
Become active If the failover link is down at
startup, both modules will become
active.
State link failed No failover No action No action State information will become out
of date, and sessions will be
terminated if a failover occurs.
Interface failure on active
module above threshold
Failover Mark active as
failed
Become active None.
Interface failure on standby
module above threshold
No failover No action Mark standby as
failed
When the standby module is
marked as failed, then the active
module will not attempt to fail over
even if the interface failure
threshold is surpassed.
Trunk failure in inter-switch
setup
No failover No action Become active Both modules become active if all
communication between the
modules is terminated, as in the
case of a trunk failure. Neither
module receives hello messages,
and both modules assume the
active role.
Table 15-1 Failover Behavior (continued)
Failure Event Policy Active Action Standby Action Notes

Cisco Catalyst 6500 Series Specifications

General

Brand	Cisco
Model	Catalyst 6500 Series
Category	Switch
Language	English