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

Consider the following Gateway topology:

partner-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 VeloCloud Gateway, or from the VeloCloud Gateway to the Provider Edge router.
2 Call Controller The VeloCloud Gateway should be able to ping the Provider Edge router or Call Controller to verify connectivity.
3 WAN The VeloCloud 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 VeloCloud Gateway and Provider Edge router and describes the activity that occurs.

partner-gateway-failover

The Partner 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.