Create the following registry value on the Veeam Backup Server. With this setting enabled, Veeam Backup & Replication will collect the IP addresses of all NICs on the Microsoft Hyper-V server(s) or Off-host backup proxy.
Key Location: HKLM\SOFTWARE\Veeam\Veeam Backup and Replication\
Value Name: HvCollectAllHostAddresses
Value Type: DWORD (32-Bit) Value
Value Data: 1
After the registry value is created on the Veeam Backup Server, rescan the Hyper-V Hosts to update the configuration database.