• SonicOS 8
• About SonicOS
  • Working with SonicOS
  • SonicOS Workflow
  • How to Use the SonicOS Administration Guides
  • Guide Conventions
• About Network
  • DNS Introduction
• Configuring DNS Settings
  • Configuring DNS for IPv4
    • Specifying which DNS Servers are Used
    • Enabling Proxy of Split DNS Servers
    • DNS Rebinding Attack Prevention
    • DNS Rebinding and Cache Lookup
  • Configuring DNS for IPv6
    • Specifying which DNS Servers are Used
    • Enabling DNS Host Name Lookup over TCP for FQDN
  • Configuring Domain-Specific DNS Servers for Split DNS
    • About Split DNS
      • About Per-Partition DNS Servers and Split DNS
    • Adding a Split DNS Server
    • Editing Split DNS Entries
    • Deleting Split DNS Entries
• Configuring Dynamic DNS
  • About Dynamic DNS
    • Supported DDNS Providers
  • Dynamic DNS Profiles
    • Configuring Dynamic DNS Profiles
    • Editing Dynamic DNS Profiles
    • Deleting Dynamic DNS Profiles
• Configuring DNS Proxy Settings
  • About DNS Proxy
    • Supported Interfaces
    • DNS Server Liveness Detection and Failover
    • DNS Cache
    • High Availability Stateful Synchronization of DNS Cache
    • DHCP Server
  • Enabling Log Settings
  • Monitoring Packets
  • Configuring DNS Proxy Settings
    • Configuring DNS Proxy Settings
    • Deleting Static DNS Cache Entries
    • Viewing DNS Proxy Cache Objects
    • Flushing Dynamic DNS Cache Entries
• SonicWall Support
  • About This Document

DNS Server Liveness Detection and Failover

When multiple DNS servers are configured, to determine the “best” server, SonicOS considers these factors:

• DNS server priority
• DNS server status (up, down, unknown)
• Time duration after failover