You can use a Sync-Failover device group in a variety of ways. This sample configuration shows two separate Sync-Failover device groups in the local trust domain. Device group A is a standard active-standby configuration. Prior to failover, only Bigip1 processes traffic for application A. This means that Bigip1 and Bigip2 synchronize their configurations, and Bigip1 fails over to Bigip2 if Bigip1 becomes unavailable. Bigip1 cannot fail over to Bigip3 or Bigip4 because those devices are in a separate device group.

Device group B is also a standard active-standby configuration, in which Bigip3 normally processes traffic for application B. This means that Bigip3 and Bigip4 synchronize their configurations, and Bigip3 fails over to Bigip4 if Bigip3 becomes unavailable. Bigip3 cannot fail over to Bigip1 or Bigip2 because those devices are in a separate device group.

Sample Sync-Failover device groups in a trust domain

The following configuration restrictions apply to Sync-Failover device groups:

• A specific BIG-IP device in a trust domain can belong to one Sync-Failover device group only.
• On each device in a Sync-Failover device group, the BIG-IP system automatically assigns the device group name to the root and /Common folders. This ensures that the system synchronizes any traffic groups for that device to the correct devices in the local trust domain.
• The BIG-IP system creates all device groups and traffic-groups in the /Common folder, regardless of the partition to which the system is currently set.
• If no Sync-Failover device group is defined on a device, then the system sets the device group value that is assigned to the root and /Common folders to None.
• By default, on each device, the BIG-IP system assigns a Sync-Failover device group to any sub-folders of the root or /Common folders that inherit the device group attribute.
• You can configure a maximum of 15 floating traffic groups for a Sync-Failover device group.

1. On the Main tab, click Device Management > Device Groups.
2. On the Device Groups list screen, click Create. The New Device Group screen opens.
3. Type a name for the device group, select the device group type Sync-Failover, and type a description for the device group.
4. From the Configuration list, select Advanced.
5. In the Configuration area of the screen, select a host name from the Available list for each BIG-IP device that you want to include in the device group, including the local device. Use the Move button to move the host name to the Includes list. The Available list shows any devices that are members of the device's local trust domain but not currently members of a Sync-Failover device group. A device can be a member of one Sync-Failover group only.
6. For the Network Failover setting, select or clear the check box:
   • Select the check box if you want device group members to handle failover communications by way of network connectivity. This choice is required for active-active configurations.
   • Clear the check box if you want device group members to handle failover communications by way of serial cable (hard-wired) connectivity.
   For active-active configurations, you must select network failover, as opposed to serial-cable (hard-wired) connectivity.
7. For the Automatic Sync setting, select or clear the check box:
   • Select the check box when you want the BIG-IP system to automatically sync the BIG-IP configuration data whenever a config sync operation is required. In this case, the BIG-IP system syncs the configuration data whenever the data changes on any device in the device group.
   • Clear the check box when you want to manually initiate each config sync operation. In this case, F5 networks recommends that you perform a config sync operation whenever configuration data changes on one of the devices in the device group.
8. For the Full Sync setting, select or clear the check box:
   • Select the check box when you want all sync operations to be full syncs. In this case, the BIG-IP system syncs the entire set of BIG-IP configuration data whenever a config sync operation is required.
   • Clear the check box when you want all sync operations to be incremental (the default setting). In this case, the BIG-IP system syncs only the changes that are more recent than those on the target device. When you select this option, the BIG-IP system compares the configuration data on each target device with the configuration data on the source device and then syncs the delta of each target-source pair.
   If you enable incremental synchronization, the BIG-IP system might occasionally perform a full sync for internal reasons. This is a rare occurrence and no user intervention is required.
9. In the Maximum Incremental Sync Size (KB) field, retain the default value of 1024, or type a different value. This value specifies the total size of configuration changes that can reside in the incremental sync cache. If the total size of the configuration changes in the cache exceeds the specified value, the BIG-IP system performs a full sync whenever the next config sync operation occurs.
10. Click Finished.

The most common reason to use a Sync-Only device group is to synchronize a specific folder containing policy data that you want to share across all BIG-IP devices in a local trust domain, while setting up a Sync-Failover device group to fail over the remaining configuration objects to a subset of devices in the domain. In this configuration, you are using a Sync-Only device group attribute on the policy folder to override the inherited Sync-Failover device group attribute. Note that in this configuration, Bigip1 and Bigip2 are members of both the Sync-Only and the Sync-Failover groups.

Sync-Only Device Group

To implement this configuration, you can follow this process:

1. Create a Sync-Only device group on the local device, adding all devices in the local trust domain as members.
2. Create a Sync-Failover device group on the local device, adding a subset of devices as members.
3. On the folder containing the policy data, use tmsh to set the value of the device group attribute to the name of the Sync-Only device group.
4. On the root folder, retain the default Sync-Failover device group assignment.

1. On the Main tab, click Device Management > Device Groups.
2. On the Device Groups list screen, click Create. The New Device Group screen opens.
3. Type a name for the device group, select the device group type Sync-Only, and type a description for the device group.
4. From the Configuration list, select Advanced.
5. For the Members setting, select an IP address and host name from the Available list for each BIG-IP device that you want to include in the device group. Use the Move button to move the host name to the Includes list. The list shows any devices that are members of the device's local trust domain.
6. For the Automatic Sync setting, select or clear the check box:
   • Select the check box when you want the BIG-IP system to automatically sync the BIG-IP configuration data whenever a config sync operation is required. In this case, the BIG-IP system syncs the configuration data whenever the data changes on any device in the device group.
   • Clear the check box when you want to manually initiate each config sync operation. In this case, F5 networks recommends that you perform a config sync operation whenever configuration data changes on one of the devices in the device group.
7. For the Full Sync setting, select or clear the check box:
   • Select the check box when you want all sync operations to be full syncs. In this case, the BIG-IP system syncs the entire set of BIG-IP configuration data whenever a config sync operation is required.
   • Clear the check box when you want all sync operations to be incremental (the default setting). In this case, the BIG-IP system syncs only the changes that are more recent than those on the target device. When you select this option, the BIG-IP system compares the configuration data on each target device with the configuration data on the source device and then syncs the delta of each target-source pair.
   If you enable incremental synchronization, the BIG-IP system might occasionally perform a full sync for internal reasons. This is a rare occurrence and no user intervention is required.
8. In the Maximum Incremental Sync Size (KB) field, retain the default value of 1024, or type a different value. This value specifies the total size of configuration changes that can reside in the incremental sync cache. If the total size of the configuration changes in the cache exceeds the specified value, the BIG-IP system performs a full sync whenever the next config sync operation occurs.
9. Click Finished.