Configuring Tracking And Failure Detection For A Host Or Gateway - Cisco ACE-4710-K9 Administration Manual

Chapter 7 Configuring Redundant ACE Appliances
Note

Configuring Tracking and Failure Detection for a Host or Gateway

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You must configure preemption for tracking switchover to work. For details on
preemption, see the "Configuring Preemption"
For example, suppose that on ACE 1 you configure the active FT group member
with a priority of 100 and on ACE 2 you configure the standby FT group member
with a priority of 70. Assume that you configure the FT group to track three
critical interfaces, each with a unit priority of 15. To trigger a switchover, all three
interfaces must fail so that the priority of the active member is less than the
priority of the standby member (100 – 45 = 55).
To illustrate the "any" scenario, assume the FT group members have the same
individual priorities as in the previous example (100 and 70, respectively).
However, this time you configure the three tracked interfaces, each with a unit
priority of 40. If any one of the interfaces associated with the active member goes
down, then the priority of the active member falls below the priority of the standby
member and a switchover occurs. If that failed interface later returns to service,
the ACE increments the associated group member priority by 40, and a switchover
would occur back to the original active member. To guarantee a switchover if any
tracked item goes down, configure the unit priority on each tracked item equal to
the group member's priority. In this case, you could configure the unit priority to
be 100.
This section describes how to configure tracking and failure detection for a
gateway or a host. It contains the following topics:
Creating a Tracking and Failure Detection Process for a Host or Gateway
•
Configuring the Gateway or Host IP Address Tracked by the Active Member
•
Configuring a Probe on the Active Member for Host Tracking
•
Configuring a Priority on the Active Member for Multiple Probes
•
• Configuring the Gateway or Host IP Address Tracked by the Standby Member
Configuring a Probe on the Standby Member for Host Tracking
•
Configuring a Priority on the Standby Member for Multiple Probes
•
Example of a Tracking Configuration for a Gateway
•
Cisco 4700 Series Application Control Engine Appliance Administration Guide
Configuring Tracking and Failure Detection
section.
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