• High Availability
  • About High Availability
    • High Availability Terminology
    • High Availability Modes
    • High Availability Encryption
    • Crash Detection
    • Virtual MAC Address
    • Dynamic WAN Interfaces with PPPoE HA
    • Stateful Synchronization with DHCP
    • Stateful Synchronization with DNS Proxy
    • About HA Monitoring
  • About Active/Standby HA
    • Benefits of Active/Standby HA
    • Working of Active/Standby HA
  • About Stateful Synchronization
    • Benefits of Stateful Synchronization
    • How Does Stateful Synchronization Work?
    • Example of Stateful Synchronization
  • Active/Standby and Active/Active DPI Prerequisites
    • Supported Platforms and Licensing for HA
    • Physically Connecting Your Security Appliances
    • Connecting the Active/Active DPI Interfaces for Active/Active DPI
  • Maintenance
    • Removing an HA Association
    • Replacing a SonicWall Security Appliance
      • Replacing an HA Primary Unit
      • Replacing an HA Secondary Unit
• High Availability Status
  • Active/Standby High Availability Status
    • High Availability Status
    • High Availability Config
    • High Availability Licenses
• Configuring High Availability
  • Configuring Active/Standby High Availability Settings
  • Configuring HA with Dynamic WAN Interfaces
  • Configuring Network DHCP and Interface Settings
    • Disabling the SonicOS DHCP Server
    • Configuring Virtual IP Addresses
    • Configuring Redundant Ports
• Fine Tuning High Availability
  • Advanced Settings
  • Configuring Advanced High Availability Settings
• Monitoring High Availability
  • Configuring Active/Standby High Availability Monitoring
  • IPv6 High Availability Monitoring
  • IPv6 HA Monitoring Considerations
• SonicWall Support
  • About This Document

Working of Active/Standby HA

HA requires one SonicWall Security Appliance configured as the Primary SonicWall, and an identical Security Appliance configured as the Secondary SonicWall. During normal operation, the Primary SonicWall is in an Active state and the Secondary SonicWall in an Standby state. If the Primary device loses connectivity, the Secondary SonicWall transitions to Active mode and assumes the configuration and role of Primary, including the interface IP addresses of the configured interfaces.

Basic Active/Standby HA provides stateless high availability. After a failover to the Secondary Security Appliance, all the pre-existing network connections must be re-established, including the VPN tunnels that must be re-negotiated. Stateful Synchronization can be licensed and enabled separately. For more information, see About Stateful Synchronization.

The failover applies to loss of functionality or network-layer connectivity on the Primary SonicWall. The failover to the Secondary SonicWall occurs when critical services are affected, physical (or logical) link failure is detected on monitored interfaces, or when the Primary SonicWall loses power. The Primary and Secondary SonicWall devices are currently only capable of performing Active/Standby High Availability or Active/Active DPI – complete Active/Active high availability is not supported at present.

There are two types of synchronization for all configuration settings:

• Incremental – If the timestamps are in sync and a change is made on the Active unit, an incremental synchronization is pushed to the Standby unit.
• Complete –If the timestamps are out of sync and the Standby unit is available, a complete synchronization is pushed to the Standby unit. When incremental synchronization fails, a complete synchronization is automatically attempted.