To establish a from-the-cloud connection, Cloud Proxy sends a request to the vSphere Replication Appliance on premises, using the vCloud Tunneling Agent control connection.
In response the vCloud Tunneling Agent initiates a from-the-cloud connection back to the Cloud Proxy. There is only one control connection per tenant (source site), so only one instance of Cloud Proxy can send requests to a particular vCloud Tunneling Agent. Since the load balancer can forward connections to any instance of the Cloud Proxy, the particular instance serving the client request may not have access to the control connection corresponding to the (source site). Furthermore, once from-the-cloud connection is established, there is no guarantee that this connection will be forwarded to the same instance of Cloud Proxy serving the tenant (source site).
The recommended solution consists of the following two elements.
Using an internal message bus to request from-the-cloud connection
Configure L4 or L7 load balancing mechanism (Service Providers are expected to configure the load balancer mechanism accordingly)