• SonicOS 7.1
• About SonicOS
  • Working with SonicOS
  • SonicOS Workflow
  • How to Use the SonicOS Administration Guides
  • Guide Conventions
• 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
  • Understanding High Availability
    • Understanding SonicWall High Availability Operation Modes
    • 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 Prerequisites
  • Supported Platforms and Licensing for HA
    • Physically Connecting Your Security Appliances
    • 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
• Configuration of HA Active/Standby
  • 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
  • Configuring Active/Standby High Availability Monitoring
  • IPv6 High Availability Monitoring
  • IPv6 HA Monitoring Considerations
• Azure Use Cases
  • Use Case 1: Manage Azure HA Firewall
  • Use Case 2: Forward LAN traffic to the External Network through the Gateway after HA Failover
  • Use Case 3: Configure DNAT on Azure HA Firewall
  • Use Case 4: Configure DNAT on Azure HA Firewall (Need to move multiple floating IPs support)
• SonicWall Support
  • About This Document

Example of Stateful Synchronization

In case of a failover, the following sequence of events occurs:

1. A PC user connects to the network, and the Active Security Appliance creates a session for the user.
2. The Active Security Appliance synchronizes with the Standby Security Appliance. The Standby now has all of the user’s session information.
3. The administrator restarts the Active unit.
4. The Standby unit detects the restart of the Active unit and switches from Standby to Active.
5. Now Active Security Appliance begins to send gratuitous ARP messages to the connected switches using the same Virtual MAC address and IP address as the Active Security Appliance. No routing updates are necessary for downstream or upstream network devices.
6. When the PC user attempts to access a Web page, now Active Security Appliance has all of the user’s session information and is able to continue the user’s session without interruption.