For an on-premises Nutanix cluster to establish a connection and replicate data to a Nutanix Cloud AZ, it must be able to communicate with the public endpoints of the cloud service over the internet. This requires the on-premises cluster's Controller VMs (CVMs) to have a configured external IP address or be behind a Network Address Translation (NAT) gateway that provides outbound internet access. Without this external connectivity, the initial pairing and subsequent replication traffic from the on-prem AZ to the cloud AZ cannot be established, leading to an immediate failure.

A. Nutanix DR supports cross-hypervisor replication (e.g., ESXi on-prem to AHV in the cloud), so identical hypervisors are not a prerequisite.

C. Data efficiency settings like deduplication are generally compatible with replication and would not cause a fundamental connection failure.

D. Synchronous replication is not supported for DR to a geographically distant cloud AZ due to its strict low-latency requirements. Asynchronous replication is used instead.

- Nutanix Disaster Recovery Guide v6.0, Chapter: "Availability Zone and Network Connection Setup", Section: "Setting Up a Nutanix Cloud AZ as a Recovery AZ". The guide explicitly lists as a prerequisite: "Configure an external IP address for the on-prem cluster."

- Nutanix Cloud Services - Disaster Recovery Onboarding and User Guide, Section: "Prerequisites". This document outlines the networking requirements, including the need for the on-prem cluster to have internet access to communicate with the Nutanix Cloud control plane.