If you intensively use virtualization you may noticed that when you restore very old backup of Domain Controller (just copy of VM or just old backup) you may confront with the problem named “USN rollback”. In this case your restored VM for Domain Controller will not replicate with other Domain Controllers.

The simplest and free way to avoid a such problem is to use for backup builtin WSB/Windows Server Backup – enough to backup only System State, or if you have space BMR/bare metal recovery (allegedly only this Microsoft tool is AD aware backup tool and during restoration deletes/fixes some specific registry/AD insides to mitigate USN rollback). After that you can re-backup again this backups by Veeam and other backup tools (usually i create second virt disk for a such WSB backups – DC VM backups itself by WSB to own second vhd/vmdk and Veeam later on makes backup of whole VM. To reduce size of WSB backups use my other post about retention configuration for Windows Server Backup.