Explanation
To enable stateful active-active SNAT on a Tier-0 or Tier-1 gateway, you must configure an Interface Group for the NSX Edge uplinks. An Interface Group is a logical grouping of NSX Edge interfaces that belong to the same failure domain. A failure domain is a set of NSX Edge nodes that share the same physical network infrastructure and are subject to the same network failures. By configuring an Interface Group, you can ensure that the stateful services are distributed across different failure domains and can recover from network failures1