F5 Cloud Failover

Welcome to the F5 Cloud Failover User Guide. To provide feedback on this documentation, you can file a GitHub Issue.

Introduction

The F5 Cloud Failover Extension (CF) is an iControl LX extension that provides L3 failover functionality in cloud environments, effectively replacing Gratuitous ARP (GARP). Cloud Failover uses a declarative model, meaning you provide a JSON declaration using a single REST API call. The declaration represents the configuration that Cloud Failover is responsible for creating on a BIG-IP system.

How does it work?

In the event of a failover between BIG-IP systems, BIG-IP fails a traffic group over, which runs the /config/failover/tgactive script. The Cloud Failover Extension updates that file during any configuration request to ensure it triggers failover by calling the Cloud Failover /trigger API. During a failover event, CF then moves or updates cloud resources as described below:

  • Failover IP(s): The extension updates IP configurations between NICs, updates EIP/private IP associations, and updates forwarding rule target instances.
  • Failover Routes: The extension updates Azure User-Defined Routes (UDR), AWS route tables, and GCP forwarding rule targets to point to a self IP address of the active BIG-IP device.
  • Failback: The extension reverts to using the designated primary BIG-IP when it becomes active again.

The diagram below shows a typical failover scenario for an active/standby pair of BIG-IPs in an Azure cloud environment. To see how Cloud Failover Extension works in other cloud environments, see the corresponding sections for AWS and Google Cloud.

_images/AzureFailoverExtensionHighLevel.gif

Why use Cloud Failover Extension?

Using Cloud Failover Extension has three main benefits:

  • Standardization: Failover patterns will look similar across all clouds.
  • Portability: You can leverage a variety of methods, including cloud-native templates, Terraform, and Ansible, to install and run CF.
  • Lifecycle and Supportability: You can upgrade BIG-IP without having to call F5 support to fix failover.

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