Managing Configuration Synchronization

About configuration synchronization

Configuration synchronization (also known as config sync) is the operation that the BIG-IP system performs to propagate BIG-IP configuration changes, including device trust information, to all devices in a device group. BIG-IP devices that contain the same configuration data can work in tandem to more efficiently process application traffic on the network.

If you want to exclude certain devices from config sync, you simply exclude them from membership in that particular device group.

You can sync some types of data on a global level across all BIG-IP devices, while syncing other data in a more granular way, on an individual application level to a subset of devices. For example, you can set up a large device group to sync resource and policy data (such as iRules and profiles) among all BIG-IP devices in a data center, while setting up a smaller device group for syncing application-specific data (such as virtual IP addresses) between the specific devices that are delivering those applications.

Whenever synchronization occurs, either automatically or manually, the BIG-IP system attempts to optimize performance by syncing only the data that changed since the last config sync operation.

Important: To synchronize configuration data among device group members, all members must be running the same version of the BIG-IP system software.

Specifying an IP address for config sync

Before configuring the config sync address, verify that all devices in the device group are running the same version of BIG-IP system software.

You perform this task to specify the IP address on the local device that other devices in the device group will use to synchronize their configuration objects to the local device.

Note: You must perform this task locally on each device in the device group.

1. Confirm that you are logged in to the 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. Near the top of the screen, click ConfigSync.

5. From the Local Address list, retain the displayed IP address or select another address from the list.

   F5 Networks recommends that you use the default value, which is the self IP address for the internal VLAN. This address must be a non-floating (static) self IP address and not a management IP address.

   Important: If the BIG-IP device you are configuring is accessed using Amazon Web Services, then the internal self IP address that you select must be an internal private IP address that you configured for this EC2 instance as the Local Address.

6. Click Update.

After performing this task, the other devices in the device group can synchronize their configurations to the local device whenever a sync operation is initiated.

Viewing config sync status for the local device

You can use the BIG-IP Configuration utility to view the config sync status of the local device relative to the other members of the device group. If you have configured the device group for manual synchronization, you can use the config sync status information to determine whether you need to perform a manual sync operation.

1. Display any BIG-IP Configuration utility screen.

2. In the upper left corner of the screen, view the status of the device group:

   • If the sync status is green (In Sync), the local device is synchronized with all device group members, and you do not need to perform a config sync operation.
   • If the sync status is yellow (Changes Pending), the BIG-IP configuration on the local device is out of sync with one or more device group members, or device trust is not fully established. You must therefore ensure that a config sync operation occurs for the relevant device group. If the Automatic Sync setting is enabled for the device group, the BIG-IP system synchronizes the configuration automatically, and no user action is required.

For more details, you can click the status, which displays the Overview screen. Using this screen, you can view a detailed message about the status, as well as the status of each device group member.

Viewing config sync status for all device groups and members

You can use the BIG-IP Configuration utility to view the config sync status of any device group and each of its members, including the special Sync-Only device group for device trust. If the Automatic Sync setting is disabled for a device group, you can use the config sync status information to determine whether you need to do a manual sync operation.

1. On the Main tab, click Device Management > Overview.

2. In the Device Groups area of the screen, click the arrow next to the name of the relevant device group.

   The screen expands to show a summary and details of the sync status of the selected device group, as well as a list of the individual devices within the device group.

3. In the Devices area of the screen, view the sync status of each device:

   • If all devices show a sync status of green, the configurations of all device members are synchronized, and you do not need to perform a config sync operation. Here is a sample Overview screen showing a status of In Sync:

     

   • If any device shows a sync status of Changes Pending, you must synchronize the configuration on that device to the other members of the device group. Here is a sample Overview screen showing a status of Changes Pending:

     

   A status of Changes Pending for a device indicates that the device contains recent configuration changes that have not yet been synchronized to the other members of the device group.

Manually synchronizing the BIG-IP configuration

Before you perform this task, verify that device trust has been established and that all devices that you want to synchronize are members of a device group.

You perform this task when the automatic sync feature is disabled and you want to manually synchronize BIG-IP configuration data among the devices in the device group. This synchronization ensures that any device in the device group can process application traffic successfully. You can determine the need to perform this task by viewing sync status in the upper left corner of any BIG-IP Configuration utility screen. A status of Changes Pending indicates that you need to perform a config sync within the device group.

Important: You can log into any device in the device group to perform this task.

1. On the Main tab, click Device Management > Overview.

2. In the Device Groups area of the screen, click the arrow next to the name of the relevant device group.

   The screen expands to show a summary and details of the sync status of the selected device group, as well as a list of the individual devices within the device group.

3. In the Devices area of the screen, choose a device.

4. In the Sync Options area of the screen, choose an option:

   Option	Description
   Push the selected device configuration to the group	Select this option when you want to synchronize the configuration of the selected device to the other device group members.
   Pull the most recent configuration to the selected device	Select this option when you want to synchronize the most recent configurations of one or more device group members to the selected device.

5. Click Sync.

After you initiate a manual config sync, the BIG-IP system compares the configuration data on the local device with the data on each device in the device group, and synchronizes the most recently-changed configuration data from one or more source devices to one or more target devices. Note that the system does not synchronize non-floating self IP addresses.

About automatic vs. manual sync

You can configure the BIG-IP system to synchronization configuration data automatically, or you can manually initiate synchronization:

Automatic

Automatic synchronization (also known as auto sync) ensures that the BIG-IP system automatically synchronizes the configuration among device group members whenever you make a change to any one of those devices.

Manual

If you do not enable auto sync, you must manually synchronize the BIG-IP configuration among device group members to ensure that the devices remain in sync. With manual synchronization, the BIG-IP system notifies you whenever configuration data within the group has changed and therefore needs to be synchronized.

Enabling and disabling automatic sync

You can use the BIG-IP Configuration utility to enable or disable automatic synchronization for device groups. When you enable automatic synchronization, a BIG-IP device in the device group automatically synchronizes its configuration data to the other members of the device group whenever its configuration data changes.

By default, the BIG-IP system syncs only the data that changed since the previous sync, rather than the entire set of configuration data.

1. On the Main tab, click Device Management > Device Groups.

2. In the Group Name column, click the name of the relevant device group.

3. For the Automatic Sync setting, select or clear the check box:

After you enable automatic sync, the BIG-IP system automatically syncs future configuration changes to each device group member.

Whenever an automatic sync operation occurs, you must log in to each device group member and use the Traffic Management shell to save the configuration on the device. An alternative is to configure the tmsh save-on-auto-sync option for the device group.

About full vs. incremental sync

You can configure the BIG-IP system to perform either full or incremental synchronization operations whenever a config sync is required:

Full

When you enable full sync, the BIG-IP system syncs the entire set of BIG-IP configuration data whenever a config sync operation occurs. You can only do a full sync operation if you have enabled manual sync; Full sync operations are not available when automatic sync is enabled.

Incremental

When you enable incremental sync, the BIG-IP system syncs only the changes that are more recent than those on the target device. The BIG-IP system accomplishes this by comparing the commit ID and configuration changes, and then applying the delta. F5 networks recommends that you use incremental sync, for optimal performance. The incremental sync feature is a performance improvement feature and is the default value. You can use incremental sync with either automatic or manual sync operations.

You can also configure the cache size for any configuration changes slated for incremental sync. (This applies to incremental sync only.) For example, using the default cache size value of 1024, if you make more than 1024 KB worth of incremental changes, the system performs a full synchronization operation. Using incremental synchronization operations can reduce the per-device sync/load time for configuration changes.

Enabling and disabling full sync

You can enable or disable full synchronization for device groups. When you enable full sync, the BIG-IP system syncs the entire set of configuration data whenever a sync operation occurs. When you disable full synchronization, the BIG-IP system performs incremental synchronization, which causes the system to sync only the changes that are more recent than the changes on the target device. The incremental sync feature is a performance improvement feature.

1. On the Main tab, click Device Management > Device Groups.

2. In the Group Name column, click the name of the relevant device group.

3. For the Full Sync setting, specify whether the system synchronizes the entire configuration during synchronization operations:

   • Select the check box when you want all sync operations to be full syncs. In this case, every time a config sync operation occurs, the BIG-IP system synchronizes all configuration data associated with the device group. This setting has a performance impact and is not recommended for most customers.
   • 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.

4. Click Update.

After you configure this feature, the BIG-IP system performs either a full or an incremental sync whenever a sync operation occurs.

Troubleshooting the config sync process

The BIG-IP® Configuration utility displays a number of different statuses and messages to help you diagnose and correct a config sync problem. These statuses and messages pertain to both device groups and individual device group members.

Sync status for device groups

At all times, the BIG-IP system displays a specific sync status for each device group.

Sync status for device group members

At all times, the BIG-IP system displays a specific sync status for each device within a device group.

Advanced config sync properties for a device

A device in a device group has several advanced properties.