The primary benefit of configuring replica mapping in Veeam Backup & Replication is C: Reduced WAN traffic. Replica mapping is a feature that allows an administrator to map an existing VM in the disaster recovery site to a replica job. This is particularly useful when the initial replication of a large VM has been performed by other means (such as shipping a hard drive with the VM data to the DR site) or if a replica VM already exists and needs to be re-synced with the source VM. By using replica mapping, Veeam can avoid transferring the entire VM over the WAN again and instead only synchronize the differences between the source VM and the existing replica. This significantly reduces the amount of data that needs to be transferred over the WAN, conserving bandwidth and speeding up the replication process. It's an efficient way to manage replicas, especially for large VMs or in environments with limited bandwidth.

Having at least one backup proxy server in each site when defining a replica job is recommended because the backup proxy servers are responsible for data processing and transfer. Having proxies in both sites enables a stable connection for VM data transfer across sites, as they handle the data compression, deduplication, and transfer processes. This setup ensures that data is efficiently moved from one site to another, thereby making replication more resilient and reliable. Proxies do not automatically restart replication after failure (A), remove the need for VM snapshots during transit (B and F), or enable automatic WAN acceleration (D), although they can work in conjunction with WAN accelerators if configured to do so. They also don't directly deduplicate data during transit across the WAN (C), although they do compress and optimize it for transfer.

https://helpcenter.veeam.com/docs/backup/hyperv/forward_incremental_backup.html?ver=

To ensure that the VM data remains encrypted throughout the backup process, the job should be configured to use the proxies with the NBDSSL (Network Block Device SSL) transport mode. This mode encrypts data transferred over the network, adhering to the company policy that prioritizes data security. While DirectSAN Access is fast, it does not provide encryption of in-flight data.