What does "Spare Mode" do?

What does "Spare Mode" do?

Traffic carried via Big Network SD-WAN is transported via all available WAN links (except those marked in "Spare Mode") by using a balanced flow based allocation scheme. Quality of Service (QoS) probes are launched via each path every 250ms to evaluate path availability. Active flows directed to dead paths are automatically re-allocated to live paths.

A WAN port may be marked into "Spare Mode". When in Spare Mode, the WAN port will not be used for SD-WAN traffic unless all other non-Spare Mode WAN ports become unavailable based upon WAN monitoring probes to Cloudflare's DNS Network ( and Google's DNS Network (

For more information on SD-WAN and high availability networks, please see our Product Guide.

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