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sol13887: Forcing a BIG-IP device group member to initiate a ConfigSync operation
How-ToHow-To

Original Publication Date: 09/21/2012
Updated Date: 04/04/2014

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

Purpose

You should consider using this procedure under the following condition:

  • You want to force a specific device group member to initiate a configuration synchronization (ConfigSync). For example, this procedure may be useful to force a device group member with an older configuration to synchronize its configuration to devices with a newer configuration.

Prerequisites

You must meet the following prerequisites to use this procedure:

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

Description

The BIG-IP system uses time stamps 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 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: 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 typing the following command:

    tmsh

  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, type the following command:

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

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