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Manual Chapter: Failsafe
Manual Chapter
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About system fail-safe

When you configure system fail-safe, the BIG-IP system monitors various hardware components, as well as the heartbeat of various system services, and can take action if the system detects a heartbeat failure.

You can configure the BIG-IP system to monitor the switch board component and then take some action if the BIG-IP system detects a failure. Using the Configuration utility, you can specify the action that you want the BIG-IP system to take when the component fails. Possible actions that the BIG-IP system can take are:

  • Reboot the BIG-IP system.
  • Restart all system services.
  • Go offline.
  • Go offline and cancel the TMM service.
  • Fail over and restart TMM.

You configure system fail-safe from the System > High Availability screen.

About VLAN fail-safe

For maximum reliability, the BIG-IP system supports failure detection on all VLANs. When you configure the fail-safe option for a VLAN, the BIG-IP system monitors network traffic going through that VLAN. If the BIG-IP system detects a loss of traffic on the VLAN and the fail-safe timeout period has elapsed, the BIG-IP system attempts to generate traffic by issuing ARP requests to nodes accessible through the VLAN. The BIG-IP system also generates an ARP request for the default route, if the default router is accessible from the VLAN. Failover is averted if the BIG-IP system is able to send and receive any traffic on the VLAN, including a response to its ARP request.

For a redundant system configuration, if the BIG-IP system does not receive traffic on the VLAN before the timeout period expires, the system can initiate failover to another device group member, reboot, or restart all system services. For a single device configuration, the system can either reboot or restart all system services. The default action for both configurations is Reboot.

Warning: You should configure the fail-safe option on a VLAN only after the BIG-IP system is in a stable production environment. Otherwise, routine network changes might cause failover unnecessarily.

Each interface card installed on the BIG-IP system is typically mapped to a different VLAN. Thus, when you set the fail-safe option on a particular VLAN, you need to know the interface to which the VLAN is mapped. You can use the BIG-IP Configuration utility to view VLAN names and their associated interfaces.

There are two ways to configure VLAN fail-safe in the BIG-IP Configuration utility: from the System > High Availability > VLANs > Add VLAN screen or from the Network > VLANs > New VLAN screen.

About gateway fail-safe

One type of network failure detection is known as gateway fail-safe, which applies to redundant system configurations only. Gateway fail-safe monitors traffic between an active BIG-IP system in a device group and a pool containing a gateway router. You configure the gateway fail-safe feature if you want the BIG-IP system to take an action, such as failover, whenever some number of gateway routers in a pool of routers becomes unreachable.

You can configure gateway fail-safe using the BIG-IP Configuration utility. Configuring gateway fail-safe means designating a pool of routers as a gateway fail-safe pool. When you designate a pool as a gateway fail-safe pool, you provide the following information:

  • The name of the pool
  • The name of a BIG-IP device in a device group (either the local device or any other device group member)
  • The minimum number of gateway pool members that must be available to avoid the designated action
  • The action that the BIG-IP system should take when the number of available gateway pool members drops below the designated threshold. The default value is Failover.

After you configure gateway fail-safe, specifying an action of Failover, the named BIG-IP device (and only that device) fails over to another device group member whenever the number of available pool members falls below the specified threshold. Although all device group members share their pool configurations, each device ignores any gateway fail-safe configuration that does not specify itself as the device associated with the specified gateway pool.

You configure gateway fail-safe from the System > High Availability > Fail-safe > Gateway screen.

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