PowerVault 745N - specifying network range for client group access

Hi DELL'ers,

I am trying to configure a PowerVault 745N NAS, sharing a sinlge NFS share between 300 hundred clients.  There is a facility to enter client IP addresses and specify read only, read write or no access, this is in addition to the ALL-MACHINES group which is a default group.  I can only enter IP addresses and even then I tried entering 150 IP addresses in a single group but when I saved it and went back to edit the group it appeared to be empty.

So basicall is there a way to restrict access to 300+ NFS clients for a745N PowerVault?

Thanks in advance,

Peter