Is the configuration automatically synchronized between cluster members?

Short answer

Yes. While Clustering Enabled is on and Manual Sync Mode is off (default), the configuration is transferred automatically to the other device regardless of which of the two devices the change is made on; synchronization is bidirectional. The Load Balancer, network, firewall and management access, users, GTM, authentication servers, NTP, notification, log and file transport settings are synchronized. The Device DNS settings and the device-specific cluster settings (Clustering Enabled, Cluster ID, Manual Sync Mode, Sync Interface) are not synchronized. The status is monitored from the Sync. Summary row on the HA Clustering & Sync screen; if Manual Sync Mode is on, or for changes made while the connection is down, the changes are sent manually with Synchronize.

What Is Synchronized?

Synchronized	Not synchronized
Traffic manager (Load Balancer), Network, Host FW & access, Global Traffic Manager, Users, IP intelligence	Device DNS settings
IP Intelligence Management, LDAP, Radius, TACACS, User management, NTP, Localization, Update, Disk management	Clustering Enabled, Cluster ID, Manual Sync Mode
Notification settings, E-mail settings, SNMP settings, Contact groups, Notifications, Log transports, File transports, Backup settings	Sync Interface (Hardware Management)

The full list of fields is seen in the Sync. Summary table (Sync Summary).

How Is the Status Monitored?

1. The Settings → Device Management → HA Clustering & Sync screen is opened.
2. Synced is expected in the Sync. Summary row. Other values: Syncing, Pending, Error, Cluster Disconnected (the cluster connection is down) and Cluster out of sync (the configurations of the two devices differ).
3. The field table is opened with the eye icon to the left of the row label; a field whose Pending value is greater than zero, or a field that is not synchronized, is looked for. While synchronization is in progress, the Active Operations panel appears.

Manual Synchronization

• Turning automatic synchronization off or on: On the HA Clustering & Sync screen, Edit → Manual Sync Mode → Submit; the setting is made separately on each device. While it is on, it is shown with an orange hand icon in the Cluster Status row, and the changes remain local.
• Synchronize: On the device where the configuration is correct, the Synchronize button is pressed and confirmed; the entire configuration of this device is sent to the other device. While a field is being synchronized, or before 30 seconds have passed since the last run, it cannot be run again.
• While the connection is down: A change is applied only on the device where it is made; when the connection returns, the status appears as Cluster out of sync (behavior in cluster mode). The difference is resolved with Synchronize on the device where the correct configuration is.

Common Misconceptions

• "Synchronize merges the two devices." Synchronize writes the configuration of this device over the other device; if it is run on the wrong device, the recent changes are lost.
• "When the cluster settings are made on one device, they also pass to the other." Clustering Enabled, Cluster ID, Manual Sync Mode and Sync Interface are configured separately on each device.
• "The DNS settings are also synchronized." The Device DNS settings are deliberately not synchronized.
• "For synchronization, the same change must be made on both devices." The change is made on a single device; while auto sync is on, it is transferred to the other device on its own.

How it is done in the documentation

• HA Clustering & Sync · Manual Sync Mode
• HA Clustering & Sync · Sync Summary
• HA Clustering & Sync · Synchronize

Related questions

• How does a cluster work?
• What should I watch out for when taking a device in the cluster into maintenance?
• Is TR7 itself a single point of failure; how do I set up Load Balancer redundantly?