Cisco Secure Firewall Threat Defense Virtual (FTDv) appliances support High Availability (HA) configurations in specific virtual environments. The supported environments for HA setups include: * ESXi: VMware's ESXi is a widely supported platform for deploying FTDv appliances in HA configurations. * AWS: Amazon Web Services (AWS) supports FTDv appliances and allows for HA configurations to ensure redundancy and reliability in cloud deployments. These environments provide the necessary infrastructure and capabilities to support the high availability requirements for FTDv appliances. References:Cisco Secure Firewall Threat Defense Virtual Configuration Guide, Chapter on High Availability and Supported Platforms.