The BIG-IP system initiates failover according to any of several events that you define. These events fall into these categories:

System fail-safe

With system fail-safe, the BIG-IP system monitors various hardware components, as well as the heartbeat of various system services. You can configure the system to initiate failover whenever it detects a heartbeat failure.

Gateway fail-safe

With gateway fail-safe, the BIG-IP system monitors traffic between an active BIG-IP system in a device group and a pool containing a gateway router. You can configure the system to initiate failover whenever some number of gateway routers in a pool of routers becomes unreachable.

VLAN fail-safe

With VLAN fail-safe, the BIG-IP system monitors network traffic going through a specified VLAN. You can configure the system to initiate failover whenever the system detects a loss of traffic on the VLAN and the fail-safe timeout period has elapsed.

HA groups

With an HA group, the BIG-IP system monitors trunk, pool, or cluster health to create an HA health score for a device. You can configure the system to initiate failover whenever the health score falls below configurable levels.

Auto-failback

When you enable auto-failback, a traffic group that has failed over to another device fails back to a preferred device when that device is available. If you do not enable auto-failback for a traffic group, and the traffic group fails over to another device, the traffic group remains active on that device until that device becomes unavailable.

Part of configuring a Sync-Failover device group is configuring failover. Configuring failover requires you to specify certain types of IP addresses on each device. Some of these IP addresses enable continual, high availability (HA) communication among devices in the device group, while other addresses ensure that application traffic processing continues when failover occurs.

The types of IP addresses that you need to specify on each device are:

A local, static self IP address for VLAN HA

This unicast self IP address is the main address that other devices in the device group use to communicate continually with the local device to assess the health of that device. When a device in the device group fails to receive a response from the local device, the BIG-IP system triggers failover.

A local management IP address

This unicast management IP address serves the same purpose as the static self IP address for VLAN HA, but is only used when the local device is unreachable through the HA static self IP address.

One or more floating IP addresses associated with a traffic group

These are the IP addresses that application traffic uses when passing through a BIG-IP system. Each traffic group on a device includes application-specific floating IP addresses as its members. Typical traffic group members are: floating self IP addresses, virtual addresses, NAT or SNAT translation addresses, and IP addresses associated with an iApp application service. When a device with active traffic groups becomes unavailable, each of the active traffic groups becomes active on another device in the device group. This ensures that application traffic processing continues with little to no interruption.

1. Confirm that you are logged in to the actual device you want to configure.
2. On the Main tab, click Device Management > Devices. This displays a list of device objects discovered by the local device.
3. In the Name column, click the name of the device to which you are currently logged in.
4. From the Device Connectivity menu, choose Failover.
5. For the Failover Unicast Configuration settings, click Add for each IP address on this device that other devices in the device group can use to exchange failover messages with this device. The unicast IP addresses you specify depend on the type of device:

   Platform	Action
   Appliance without vCMP	Type a static self IP address associated with an internal VLAN (preferably VLAN HA) and the static management IP address currently assigned to the device.
   Appliance with vCMP	Type a static self IP address associated with an internal VLAN (preferably VLAN HA) and the unique management IP address currently assigned to the guest.
   VIPRION without vCMP	Type a static self IP address associated with an internal VLAN (preferably VLAN HA). If you choose to specify unicast addresses only (and not a multicast address), you must also type the existing, static management IP addresses that you previously configured for all slots in the cluster. If you choose to specify one or more unicast addresses and a multicast address, then you do not need to specify the existing, per-slot static management IP addresses when configuring addresses for failover communication.
   VIPRION with vCMP	Type a self IP address that is defined on the guest and associated with an internal VLAN on the host (preferably VLAN HA). If you choose to specify unicast failover addresses only (and not a a multicast address), you must also type the existing, virtual static management IP addresses that you previously configured for all slots in the guest's virtual cluster. If you choose to specify one or more unicast addresses and a multicast address, you do not need to specify the existing, per-slot static and virtual management IP addresses when configuring addresses for failover communication.

   Important: Failover addresses should always be static, not floating, IP addresses.
6. To enable the use of a failover multicast address on a VIPRION platform (recommended), then for the Use Failover Multicast Address setting, select the Enabled check box.
7. If you enabled Use Failover Multicast Address, either accept the default Address and Port values, or specify values appropriate for the device. If you revise the default Address and Port values, but then decide to revert to the default values, click Reset Defaults.
8. Click Update.

Each device or guest in a DSC device group needs specific failover IP addresses configured on it that other devices in the device group can use for failover communication with that device. The type of failover addresses required on each device varies depending on whether the system is provisioned for vCMP.

Each device or guest in a DSC device group needs specific failover IP addresses configured on it that other devices in the device group can use for failover communication with that device. The type of failover addresses required on each device varies depending on whether the system is provisioned for vCMP and whether a multicast failover address is being used.

Any traffic group that you explicitly create on the BIG-IP system is a floating traffic group. The types of configuration objects that you can associate with a floating traffic group are:

• Virtual IP addresses
• NATs
• SNAT translation addresses
• Self IP addresses
• Folders (such as an iApps folder)

You can associate configuration objects with a traffic group in these ways:

• You can rely on the folders in which the objects reside to inherit the traffic group that you assign to the root folder.
• You can use the BIG-IP Configuration utility to directly associate a traffic group with an iApp application service, a virtual IP address, a NAT or SNAT translation address, or a floating self IP address.
• You can use the BIG-IP Configuration utility to directly associate a traffic group with a folder.

Each BIG-IP device contains two pre-configured traffic groups:

• A floating traffic group named traffic-group-1 initially contains the floating self IP addresses that you configured for VLANs internal and external, as well as any iApps application services, virtual IP addresses, NATs, or SNAT translation addresses that you have configured on the device.
• A non-floating traffic group named traffic-group-local-only contains the static self IP addresses that you configured for VLANs internal and external. This traffic group never fails over to another device.

The following considerations apply to traffic groups:

• On each device in a Sync-Failover device group, the BIG-IP system automatically assigns the default floating traffic group name to the root and /Common folders.
• The BIG-IP system creates all traffic groups in the /Common folder, regardless of the partition to which the system is currently set.
• Any traffic group named other than traffic-group-local-only is a floating traffic group.
• You can specify a floating traffic group on a folder only when the device group that is set on the folder is a Sync-Failover type of device-group.
• You can set a floating traffic group on only those objects that reside in a folder with a device group of type Sync-Failover.
• Setting the traffic group on a failover object to traffic-group-local-only prevents the system from synchronizing that object to other devices in the device group.

1. On the Main tab, click Device Management > Traffic Groups.
2. On the Traffic Group List screen, click Create.
3. In the Name field, type a name for the new traffic group.
4. In the Description field, type a description for the new traffic group.
5. In the MAC Masquerade Address field, type a MAC masquerade address. When you specify a MAC masquerade address, you reduce the risk of dropped connections when failover occurs. This setting is optional.
6. From the Failover Methods list, select a failover method:
   • Select Load Aware when the device group contains heterogeneous platforms and you want to ensure that a traffic group fails over to the device with the most capacity at the moment that failover occurs.
   • Select HA Order to cause the traffic group to fail over to the first available device in the Failover Order list.
   • Select HA Group to cause the BIG-IP system to trigger failover based on an HA health score for the device.
7. If you configured the Failover Methods setting with a value of Load Aware, then in the HA Load Factor field, specify a value that represents the application load for this traffic group relative to other active traffic groups on the local device. Otherwise, skip this step.
   Important: If you configure this setting, you must configure the setting on every traffic group in the device group.
8. If you configured the Failover Methods setting with a value of HA Order, then configure the following settings. Otherwise, skip this step.
   1. Select or clear the check box for the Auto Failback option.
   2. If Auto Failback is selected, then in the Auto Failback Timeout field, type the number of seconds that you want the system to wait before failing back to the specified device. The range in seconds is from 0 to 300. The default is 60. A value of 40 to 60 seconds allows for state mirroring information to be re-mirrored for traffic groups.
   3. For the Failover Order setting, in the Available box, select a device name and using the Move button, move the device name to the Enabled box. Repeat for each device that you want to include in the ordered list. This setting is optional. Only devices that are members of the relevant Sync-Failover device group are available for inclusion in the ordered list. If you have enabled the auto-failback feature on the traffic group, ensure that the first device in the ordered list is the device to which you want this traffic group to fail back to when that first device becomes available. If auto-failback is enabled and the first device in the Failover Order list is unavailable, no auto-failback occurs and the traffic group continues to run on the current device. Also, if none of the devices in the list is currently available when failover occurs, the BIG-IP system ignores the Failover Order setting and performs load-aware failover instead, using the HA Load Factor setting.
9. If you configured the Failover Methods setting with a value of HA Group, then from the HA Groups list, select the HA group that you want to associate with this traffic group.
10. Confirm that the displayed traffic group settings are correct.
11. Click Finished.

1. From the Main tab, display the properties page for an existing BIG-IP object, such as a self IP address or a virtual address. For example, from the Main tab, click Network > Self IPs, and then from the Self IPs list, click a self IP address.
2. From the Traffic Group list, select the floating traffic group that you want the BIG-IP object to join.
3. Click Update.

1. On the Main tab, click Device Management > Traffic Groups.
2. In the Name column, view the names of the traffic groups on the local device.

1. On the Main tab, click Device Management > Traffic Groups.
2. In the Name column, click the name of the traffic group for which you want to view the associated objects. This displays a list of all failover objects for the traffic group.

This table lists and describes the properties of a traffic group.

1. Display any screen of the BIG-IP Configuration utility.
2. In the upper left corner of the screen, view the failover state of the device.

1. On the Main tab, click Device Management > Traffic Groups.
2. In the Failover Status area of the screen, view the state of all traffic groups on the device.

1. Log in to the device on which the traffic group is currently active.
2. On the Main tab, click Device Management > Traffic Groups.
3. In the Name column, locate the name of the traffic group that you want to run on the peer device.
4. Select the check box to the left of the traffic group name. If the check box is unavailable, the traffic group is not active on the device to which you are currently logged in. Perform this task on the device on which the traffic group is active.
5. Click Force to Standby. This displays target device options.
6. Choose one of these actions:
   • If the device group has two members only, click Force to Standby. This displays the list of traffic groups for the device group and causes the local device to appear in the Next Active Device column.
   • If the device group has more than two members, then from the Target Device list, select a value and click Force to Standby.

Load-aware failover is a BIG-IP feature designed for use in a Sync-Failover device group. Configuring load-aware failover ensures that the traffic load on all devices in a device group is as equivalent as possible, factoring in any differences in device capacity and the amount of application traffic that traffic groups process on a device. The load-aware configuration option is most useful for device groups with heterogeneous hardware platforms or varying application traffic loads (or both).

For example, suppose you have a heterogeneous three-member device group in which one device (Bigip_C) has twice the hardware capacity of the other two devices (Bigip_A and Bigip_B).

If the device group has four active traffic groups that each process the same amount of application traffic, then the load on all devices is equivalent when devices Bigip_A and Bigip_B each contain one active traffic group, while device Bigip_C contains two active traffic groups.

The BIG-IP system implements load-aware failover by calculating a numeric, current utilization score for each device, based on numeric values that you specify for each device and traffic group relative to the other devices and traffic groups in the device group. The system then uses this current utilization score to determine which device is the best device in the group to become the next-active device when failover occurs for a traffic group.

The overall result is that the traffic load on each device is as equivalent as possible in a relative way, that is, factoring in individual device capacity and application traffic load per traffic group.

If you do not want to use the load-aware feature to determine the next-active device for a traffic group, you can configure a traffic group to use a static, ordered list of devices instead. This list of devices specifies the order in which you want those devices to become active for the traffic group if the traffic group must fail over.

If failover occurs and the first device in the list is unavailable, the BIG-IP system tries to make the traffic group active on the second device in the list. If the second device is also unavailable, the BIG-IP system tries to make the traffic group active on the third device, and so on.

If you do not specify an ordered list or if none of the devices in the list is available, the BIG-IP system attempts to use load-aware failover to choose the next-active device.

An HA group is a BIG-IP configuration object that specifies a set of trunks, pools, and/or VIPRION clusters for a device. When you associate an HA group with an instance of a traffic group on a specific device, the BIG-IP system calculates an overall health score on that device for the associated traffic group, based on trunk, pool, or cluster availability. This HA health score determines the device that the associated traffic group should be active on at any given time and then triggers failover to that device if necessary. Trunk configurations are not synchronized between devices, which means that the number of trunk members on each device in the device group can vary whenever a trunk loses or gains members, thereby affecting the health score.

The ability of an HA group to choose a next-active device and trigger failover for a traffic group distinguishes the HA groups feature from the other failover methods (load-aware failover and HA order). Although the load-aware and HA order failover methods also identify the next-active device for a traffic group, these methods do not trigger failover; instead, failover is triggered by standard system, gateway, or VLAN fail-safe configuration.

The most common reason for configuring HA groups is to ensure that a traffic group fails over to another device when trunk availability for a specific device falls below a certain level. Also, failover triggered by an HA group is noticeably faster than failover triggered by system, gateway, or VLAN failure.

As an example, suppose that Bigip_A and Bigip_B each has the traffic group traffic-group-1. If you want traffic-group-1 to always be active on the device with the highest HA score, you can create a unique HA group for that traffic group, on each device, that defines a minimum value for acceptable link availability. You can then associate the local HA group with traffic-group-1 on each device. More specifically, on Bigip_A, you can create an HA group named HA_GroupA and associate it with traffic-group-1. On Bigip_B, you can create a different HA group, HA_GroupB, and also associate it with traffic-group-1. This ensures that traffic-group-1 is always active on the device with the best link availability at any given time.