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Working with Link Controllers in a 3-DNS Sync Group
Overview of a sync group
A sync group is a group of 3-DNS Controllers and Link Controllers that share configuration information. In a sync group, the principal controller is the 3-DNS Controller that initiates metrics collection by the big3d agents, auto-discovers objects in the network, and is the preferred system on which to make configuration changes for the sync group. Both the principal 3-DNS Controller and the receiver controllers in the sync group receive broadcasts of metrics data from the big3d agents. All members of the sync group also receive broadcasts of updated configuration settings from the 3-DNS Controller that has the latest configuration changes.
Understanding how a sync group works
The sync group feature synchronizes individual configuration files, such as wideip.conf, and other files that store system settings. The 3-DNS Controllers and Link Controllers in a sync group operate as peer servers. At set intervals, the synchronization process compares the time stamps of the configuration files earmarked for synchronization on all of the sync group members. If the time stamp on a specific file differs between the members, the member with the latest file broadcasts the file to all of the other members in the sync group.
Planning a sync group
When you define the sync group, you select the sync group members from the list of 3-DNS Controllers and Link Controllers you have already defined in the 3-DNS configuration. In the Configuration utility, the sync group lists the controllers in the order in which you selected them. The first 3-DNS Controller in the list becomes the principal 3-DNS Controller. The remaining 3-DNS Controllers and Link Controllers in the list become receivers. If the principal 3-DNS Controller becomes disabled, the next 3-DNS Controller in the list becomes the principal 3-DNS Controller until the original principal 3-DNS Controller comes back online.
In a sync group, Link Controllers can be only receiver members, and you cannot create a sync group that contains only Link Controllers. You must have at least one 3-DNS Controller in a sync group.
Configuring a sync group
The following sections describe the procedures you follow to add a Link Controller into a sync group that already has at least one 3-DNS Controller configured and working properly. You may also want to review the information in the 3-DNS Administrator Guide, Chapter 10, Adding a 3-DNS Controller to an Existing Network.
Preparing to add a Link Controller to a sync group
Before you can add a Link Controller to a sync group, you should complete the following tasks:
- Physically install the Link Controller in its data center. (For more information on hardware installation, refer to the Platform Guide that shipped with the unit.)
- Run the Setup utility on the Link Controller. (For more information on the Setup utility, see the BIG-IP Reference Guide, Chapter 2, Using the Setup Utility .)
When you have finished this part of the setup for the Link Controller, do not make any other changes to the configuration.
Adding a Link Controller to a 3-DNS sync group
Once you have installed the Link Controller and run the Setup utility, you are ready to add the Link Controller to the sync group. There are three tasks to adding a Link Controller to a 3-DNS sync group:
- Run the merge_configs script on the sync group's principal 3-DNS Controller.
- Add the Link Controller to the sync group using the principal 3-DNS Controller's Configuration utility.
- Run the 3dns_add script on the Link Controller.
The following sections explain the specific steps for each of the previous tasks. You must perform these tasks in the order they are listed.
Before you add the Link Controller to the 3-DNS sync group, we recommend that you back up both the 3-DNS Controller configuration and the Link Controller configuration.
To run the merge_configs script
From the command line on the principal 3-DNS Controller, run the merge_configs script by typing the following command, where <ip_address> is the IP address of the Link Controller that you want to add to the sync group.
/usr/local/bin/merge_configs -peer <ip_address>
To make the sync group aware of the Link Controller
Using the Configuration utility on the principal 3-DNS Controller, add the Link Controller to the sync group.
- In the navigation pane, click 3-DNS Sync.
The Synchronization screen opens.
- On the toolbar, click Add to Group.
The Add a 3-DNS to a Sync Group screen opens.
- Check the box next to the Link Controller that you want to add to the sync group, and click Add.
To add the Link Controller to the sync group and start synchronization
The final step in adding the Link Controller to a 3-DNS sync group is to run the 3dns_add script on the Link Controller. The script moves the synchronized configuration to the Link Controller, and finalizes the sync group setup. You can run the 3dns_add script on the Link Controller either by using a remote secure shell session, or by using a monitor and keyboard connected directly to the controller.
- At the login prompt on the new controller, type root.
- At the password prompt, type the password you configured when you ran the Setup utility.
- To run the script, type 3dns_add at the command line.
The script performs the following tasks:
- Copies the existing controller's configuration to the new controller
- Sets up SSH communications between the new controller and existing F5 devices in the network
- Copies the existing controller's iQuery key to the new controller so communications between the controller and the big3d agents are secure
Verifying the configuration
Once the script finishes, we recommend that you verify the configuration from the principal controller in the sync group. For details on verifying the configuration, see Verifying the configuration, in the 3-DNS Administrator Guide, Chapter 10, Adding a 3-DNS Controller to an Existing Network.