I wanted to share this here as a handy reminder of how network mapping and Re-IP works.
For Microsoft VMs, Veeam Backup & Replication also automates the reconfiguration of VM IP addresses. If the IP addressing scheme in the production site differs from the DR site scheme, re-IP rules can be created for the replication job. When a failover occurs, Veeam Backup & Replication checks if any of the specified re-IP rules apply to the replica. If a rule applies, Veeam Backup & Replication mounts the VM disks of the replica to the backup server and changes its IP address configuration via the Microsoft Windows registry, all in less than a second. If the failover is undone or if you fail back to the original location, the replica IP address is changed back to its pre-failover state.
The replication process of a VM typically uses the same network configuration as the original VM, but if the DR site has a different network setup, a network mapping table can be created for the replication job. This table maps the source networks to the target networks. During each replication job run, Veeam Backup & Replication checks the original VM’s network configuration against the mapping table. If the original VM network matches a source network in the table, Veeam Backup & Replication updates the replica configuration file to replace the source network with the target one. This ensures that the VM replica always has the correct network settings required by the DR site. In the event of a failover to the VM replica, it will be connected to the appropriate network.
This information has been copied from the Veeam Forums here: https://forums.veeam.com/veeam-backup-replication-f2/dr-site-difference-between-network-mapping-and-re-ip-t45256.html