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Manual Chapter: Ensuring Correct Synchronization When Adding GTM to a Network
Manual Chapter
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Overview: Ensuring correct synchronization when adding GTM to a network

You can configure BIG-IP Global Traffic Manager (GTM) systems in collections called synchronization groups. All BIG-IP GTM systems in the same synchronization group have the same rank, exchange heartbeat messages, and share probing responsibility.

BIG-IP GTM systems in a synchronization group

What is configuration synchronization?

Configuration synchronization ensures the rapid distribution of BIG-IP Global Traffic Manager (GTM) settings to other BIG-IP systems that belong to the same synchronization group. A synchronization group might contain both BIG-IP GTM and BIG-IP Link Controller systems.

Configuration synchronization occurs in the following manner:

  • When a change is made to a BIG-IP GTM configuration, the system broadcasts the change to the other systems in the configuration synchronization group.
  • When a configuration synchronization is in progress, the process must either complete or timeout, before another configuration synchronization can occur.

About adding an additional BIG-IP GTM to your network

BIG-IP GTM systems exchange heartbeat messages when different software versions are installed on the systems. However, configuration synchronization cannot occur when different software versions are installed on the systems. Therefore, when you upgrade BIG-IP GTM, the configuration of the upgraded system does not automatically synchronize with the configuration of the systems in the synchronization group that have an older software version.

Task summary

When adding an additional BIG-IP GTM system to your network, perform the following tasks.

Defining an NTP server on the existing GTM

Define a Network Time Protocol (NTP) server on the existing BIG-IP GTM to ensure that each system in the synchronization group is referencing the same time when verifying configuration file timestamps.
  1. On the Main tab, click System > Configuration > Device > NTP. The NTP screen opens.
  2. Type an address for the NTP server in the Address field.
  3. Click Add.
  4. Click Update.
The NTP server is defined.

Enabling synchronization on the existing GTM

To ensure that this system can share configuration changes with other systems that you add to the configuration synchronization group, enable synchronization on the existing BIG-IP GTM.
  1. On the Main tab, click System > Configuration > Global Traffic > General. The General configuration screen opens.
  2. Select the Synchronization check box.
  3. In the Synchronization Time Tolerance field, type the maximum number of seconds allowed between the time settings on this system and the other systems in the synchronization group. The lower the value, the more often this system makes a log entry indicating that there is a difference.
    Tip: If you are using NTP, leave this setting at the default value of 10. In the event that NTP fails, the system uses the time_tolerance variable to maintain synchronization.
  4. In the Synchronization Group Name field, type the name of the synchronization group to which you want this system to belong.
  5. Click Update.
Synchronization is enabled on the existing BIG-IP GTM.

Creating a data center on the existing GTM

Create a data center on the existing BIG-IP GTM system to represent the location where the new BIG-IP GTM system resides.
  1. On the Main tab, click Global Traffic > Data Centers. The Data Center List screen opens.
  2. Click Create. The New Data Center screen opens.
  3. Type a name for the data center. Names must begin with a letter, and can contain only letters, numbers, and the underscore (_)character.
    Important: The data center name is limited to 63 characters.
  4. In the Location field, type the geographic location of the data center.
  5. In the Contact field, type the name of either the administrator or the department that manages the data center.
  6. Click Finished.

Defining a server on the existing GTM

Ensure that a data center where the new BIG-IP GTM system resides exists in the configuration of the existing BIG-IP GTM system.
Define a new server, on the existing BIG-IP GTM, to represent the new BIG-IP GTM system.
  1. On the Main tab, click Global Traffic > Servers. The Server List screen opens.
  2. Click Create. The New Server screen opens.
  3. In the Name field, type a name for the server. Names must begin with a letter, and can contain only letters, numbers, and the underscore (_) character.
    Important: Server names are limited to 63 characters.
  4. From the Product list, select BIG-IP System (Single). The server type determines the metrics that the system can collect from the server.
  5. In the Address List area, add the IP address of the server.
    Important: You must use a self IP address for a BIG-IP system; you cannot use the management IP address.
  6. From the Data Center list, select the data center where the server resides.
  7. From the Virtual Server Discovery list, select how you want virtual servers to be added to the system.
    Option Description
    Disabled The system does not use the discovery feature to automatically add virtual servers. This is the default value. Use this option for a standalone BIG-IP GTM or for a BIG-IP GTM/LTM combo system when you plan to manually add virtual servers to the system.
    Enabled The system uses the discovery feature to automatically add virtual servers. Use this option for a BIG-IP GTM/LTM combo system when you want BIG-IP GTM to discover BIG-IP LTM virtual servers.
    Enabled (No Delete) The system uses the discovery feature to automatically add virtual servers and does not delete any virtual servers that already exist. Use this option for a BIG-IP GTM/LTM combo system when you want BIG-IP GTM to discover BIG-IP LTM virtual servers.
  8. Click Create. The Server List screen opens displaying the new server in the list.
The status of the newly defined BIG-IP GTM system is blue, because you have not yet run the gtm_add script.

Running the gtm_add script on the new GTM

Determine the self IP address of the existing BIG-IP GTM.
Run the gtm_add script on the new BIG-IP GTM to acquire the configuration settings on the existing BIG-IP GTM.
Note: You must perform this task from the command-line interface.
  1. On the new BIG-IP GTM, log on to the command-line interface.
  2. At the BASH prompt, type tmsh, and press Enter.
  3. At the tmsh prompt, type run gtm gtm_add, and press Enter.
  4. Press the y key to start the gtm_add script.
  5. Type the IP address of the existing BIG-IP GTM, and press Enter.
  6. If prompted, type the root password, and then press Enter.

Implementation results

The new BIG-IP GTM that you added to the network is a part of a synchronization group. Changes you make to any system in the synchronization group are automatically propagated to all other systems in the group.

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