How does Fusion switch to the secondary dns server address?

Customer has a MC-9090 WM 5.0 (Fusion v2. ) .and is pulling IP/Subnet/gateway along with primary/secondary DNS address via DHCP.

Their primary DNS server went down and the 9090 would not connect to their SAP server using the FQDN. Once they changed FQDN to IP address , it connected.


How does Fusion behave regarding primary/secondary DNS addresses?