There’s a scenario when you want to restrict people from mounting things under a directory, for e.g. /home/test/ based on their IP address; but as you know the /etc/exports entry for /home/test/ which has fsid=0 must allow for Ips which is a superset of all other host entries in /etc/exports (and under /home/test); otherwise access will be denied for the other entries. Here you can use nocrossmnt. With nocrossmnt for the /etc/exports entry if you’ve mount –bind inside a directory X inside /home/test, the NFS server will not allow the client to descent into X unless you’ve another entry for X in /etc/exports and if it explicitly allows the client’s IP to mount it.
