Preferred network rules – specify IP ranges other than automatic DNS resolution receives

In the preferred network rules, you need to specify IP ranges for Microsoft Hyper-V server or Off-host backup proxy other than ranges received by automatic DNS resolution.

In the configuration database Veeam B&R stores only those IP addresses which are resolved by DNS names of hosts that you add in Backup Infrastructure.

If you want to apply preferred network rules using another IP range than the range received by automatic DNS resolution, you must collect information about all IP interfaces on Microsoft Hyper-V server or Off-host backup proxy using this registry value on the backup server:
To specify IP ranges other than ranges received by automatic DNS resolution, you must collect information about all IP interfaces on Microsoft Hyper-V server or Off-host backup proxy. 

For this, specify the following registry value on the backup server:

HKEY_LOCAL_MACHINE\SOFTWARE\Veeam\Veeam Backup and Replication\
Value: HvCollectAllHostAddresses
Enabled state: 1
Type: DWORD