FAQFirewall High Availability HA Pro – Questions & Answers for Zyxel ZLD Firewalls

In today’s always-on business environment, network reliability is critical. Zyxel’s Device HA Pro, available on Zyxel ZLD firewalls, ensures minimal downtime and seamless recovery. It provides a robust and easy-to-manage high availability (HA) solution with built-in synchronisation and monitoring features — explicitly designed for ZLD-based devices (not to be confused with HA options on Zyxel Firewall H-Series).

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Streamlined Deployment with a Dedicated Link

Traditional active/active HA setups often required complex routing knowledge and extra system resources. Device HA Pro simplifies deployment with an active/passive architecture.

• The active firewall handles all production traffic.

• The passive firewall stays in standby mode, continuously synchronizing configuration, session tables, and routing information through a dedicated HA link.

• This approach minimizes setup complexity and guarantees that the backup unit is always ready to take over.

Instant Failover Response

Device HA Pro is engineered for rapid, near-invisible failover.

• In case of hardware failure, link loss, or heartbeat signal interruption, the passive unit automatically takes control.

• The switchover typically completes within five seconds, preserving active sessions and minimizing user disruption.

• Failover occurs only when necessary, ensuring stable continuity without unnecessary role changes.

With Device HA Pro, organizations gain a resilient, automated, and easily managed HA setup for uninterrupted operations.

License Synchronization Best Practices

• In the Device HA Pro settings, make sure to configure the primary device’s serial number under “Serial number of the licensed device for license synchronization”.

• This ensures license transfer during failover.

• After synchronization, the passive device will display only a trial license, but inherits the full license set when it becomes active.

• License status can be verified anytime via myZyxel.com.

Frequently asked questions

Q: Do I need two licenses (e.g., UTM licenses) for Device HA Pro?
A: No. Only one license is required. The active device’s licenses are automatically inherited by the passive unit during failover.

Q: Is HA Pro supported in Nebula mode on USG FLEX (ZLD) or ATP (ZLD) series devices?

A: No, HA Pro is not supported in Nebula-managed mode on USG FLEX or ATP devices. However, you can still use HA Pro by switching the device to standalone (on-premise) mode.