6.3 NSX Edge Services Gateway
The NSX Edge services gateway high availability (HA) feature provides that an NSX Edge services gateway appliance is always available by installing an active pair of NSX Edge services gateways in the virtualized infrastructure. There is the option to enable high availability either when installing the NSX Edge services gateway device or on an already deployed NSX Edge services gateway instance.
The primary NSX Edge services gateway appliance is in the active state and the secondary appliance is in the standby state. The NSX Edge services gateway replicates the configuration of the primary appliance for the standby appliance. VMware recommends that the primary and secondary appliance be created on separate resource pools and datastores. If you create the primary and secondary appliances on the same datastore, the datastore must be shared across all hosts in the cluster. In this way, the high availability appliance pair can be deployed on different ESXi hosts. If the datastore is a local storage, both virtual machines are deployed on the same host.
In the operation of the primary appliance, it maintains a heartbeat with the standby appliance and sends service updates through an internal interface. If a heartbeat is not received from the primary appliance in the specified time, which is configurable, the primary appliance is declared dead. The standby appliance moves to the active state and takes over the interface configuration of the primary appliance. The standby appliance also starts the NSX Edge gateway services that were running on the primary appliance.