Dell PowerConnect 8024 User Configuration Manual page 951

Flood blocking cannot be enabled on virtual interfaces. While the feature
could be allowed on virtual interfaces, it is less likely to be used on a virtual
interface, since virtual interfaces are created specifically to allow flooding
between two backbone routers. So the option of flood blocking on virtual
interfaces is not supported.
See "Configuring Flood Blocking" on page 1025 for a configuration example.
951
Configuring OSPF and OSPFv3