Direct answer

Use a dual-WAN firewall or router with application-aware health checks. Define failover thresholds, session behaviour, DNS, VPN, inbound services and return-to-primary rules, then test them.

Common business internet failover failures

  • Cable is up but internet is unreachable
  • DNS fails while ping still works
  • VPN blocks traffic from a new public IP
  • Voice calls drop and do not re-register
  • Backup is online but saturated by updates or CCTV
  • Router reverts too early and flaps between paths

Create and test an internet failover runbook

Name the owner, monitoring channel, test frequency, escalation contacts, backup-data limits and the action if both paths fail. A tested manual fallback can be better than poorly understood automation.

Sources

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Page reviewed 1 September 2026