All NSX Edge configurations (distributed logical router control VMs and edge gateways) are backed up as part of NSX Manager backup. If NSX Manager configuration is intact, VMs on an inaccessible or failed NSX Edge appliance can be redeployed anytime from the vSphere Web Client by selecting Networking and Security > NSX Edges > Actions > Redeploy.

If you want to get the configuration of a standalone NSX Edge gateway, you can use REST API calls. These calls are useful if you want to preserve the configuration of a standalone NSX Edge gateway for future use or reference. This configuration might be useful in the event that you want to recreate a single NSX Edge gateway with an existing NSX Manager.

Details on how to use the REST API to manage VMware NSX can be found in the VMware NSX for vSphere API Guide and VMware NSX API Guide.