Based on the requirements, one of the factors that should be considered in the physical design when implementing the virtual machine replication between sites is to ensure that the proper firewall ports are open between the proxies at each site. This is because Veeam Backup & Replication uses network ports to communicate with backup infrastructure components and transfer data during replication. You need to make sure that the required ports are not blocked by firewalls or other network devices. For a list of ports used by Veeam Backup & Replication, see this article2