Purpose

You should consider using this procedure under the following condition:

• You want to force a specific device group member to initiate a ConfigSync operation. For example, this procedure might be useful when you want to force a device group member with an older configuration to synchronize its configuration to one or more devices with a newer configuration.

Prerequisites

You must meet the following prerequisites to use this procedure:

• You have access to the Traffic Management Shell (tmsh)
• You have one or more device groups configured

Description

The BIG-IP system uses timestamps as recorded by the mcpd process to determine which device group member has the latest configuration and is eligible to initiate a ConfigSync operation. Device group functionality is designed so that you can initiate a ConfigSync operation from the device group member with the newest configuration change. This behavior is intended to prevent a device with an older configuration from overwriting the configuration of one or more devices with a newer configuration.

For example, if the device group contains four members (BIGIP-1, BIGIP-2, BIGIP-3, and BIGIP-4) and you make a configuration change on BIGIP-1, you can initiate a ConfigSync operation from member BIGIP-1. In BIG-IP 11.1.0 through 11.2.0, ConfigSync functionality does not permit you to initiate a ConfigSync operation from devices BIGIP-2, BIGIP-3, or BIGIP-4. 

However, in some cases you might need to initiate a synchronization from a device with an older configuration to a device or devices with a newer configuration. For example, if you made a configuration change to BIGIP-1 and want to overwrite the change by initiating a ConfigSync from another device group member with an older configuration, such as BIGIP-2, you can temporarily set BIGIP-2 as the sync-leader and initiate a ConfigSync operation from that device. The set-sync-leader command temporarily designates a specific device group member as the synchronization leader and forces the device to initiate a one-time ConfigSync operation. To use the set-sync-leader command option, perform the following procedure.

Note: Starting in BIG-IP 11.2.1 you can force a synchronization from a device with an older configuration to a device or devices with a newer configuration using the Configuration utility. For more information, refer to SOL13920: Performing a ConfigSync using the Configuration utility.

Note: The set-sync-leader command may cause packet filter exemptions to be deleted. For information, refer to SOL14160: The set-sync-leader tmsh command option will delete configured packet filter exemptions.

Procedures

Forcing a specific device group member to initiate a one-time ConfigSync operation

To temporarily designate a specific device group member as the synchronization leader and force the device to initiate a ConfigSync operation, perform the following procedure:

Impact of procedure: The set-sync-leader command option forces the device to initiate a one-time ConfigSync operation. The command is not persistent and must be re-run upon every attempt to initiate the ConfigSync process from a device with an older configuration.

1. Log in to the Traffic Management Shell (tmsh) by entering the following command:

   tmsh

   Note: If you are currently logged in to the tmsh shell, you can skip this step.

2. Set the device as the synchronization leader of the device group and force the device to initiate the ConfigSync process by using the following command syntax:

   modify cm device-group <dg name> devices modify { <device name> {set-sync-leader}}

   For example, to set the ltm.example.com device as the synchronization leader for the MyDeviceGroup device group and initiate a ConfigSync process, enter the following command:

   modify cm device-group MyDeviceGroup devices modify { ltm.example.com { set-sync-leader } }

Supplemental Information

• SOL13590: Change in Behavior: The BIG-IP system only allows initiation of the ConfigSync process from the device with configuration changes
• SOL13649: Creating a device group using the Configuration utility
• SOL13639: Creating a device group using the Traffic Management Shell