The Partner SD-WAN Gateway provides resiliency by detecting failures and failing over to an alternate Partner SD-WAN Gateway. This includes the ability of a Partner SD-WAN Gateway to detect failure conditions and for the surrounding infrastructure to detect failures of the SD-WAN Gateway itself.

Consider the following SD-WAN Gateway topology:

This figure shows three distinct failure zones:
Failure Zone Component Description
1 Provider Edge The Provider Edge is one instance in which failure can be detected either from the Provider Edge router pinging the SD-WAN Gateway, or from the SD-WAN Gateway to the Provider Edge router.
2 Call Controller The SD-WAN Gateway should be able to ping the Provider Edge router or Call Controller to verify connectivity.
3 WAN The SD-WAN Gateway should have a stateful ping responder that responds only if the WAN zone is available.
The following figure shows a typical failure scenario that occurs between the SD-WAN Gateway and Provider Edge router and describes the activity that occurs.

The Partner SD-WAN Gateway also supports configurable route costs to allow for more flexible failure scenarios. Finally, there is an additional hand-off type required where neither NAT nor VLAN tags are applied to the packets and they are simply passed through to the Provider Edge router.