How to configure NFS firewall in RHEL7

If you intend to use NFSv4 protocol only, all you need to do is this:

firewall-cmd --permanent --zone public --add-service nfs
firewall-cmd --reload

But if you want to use NFSv3 protocol, things are more complicated.

firewall-cmd --permanent --zone public --add-service mountd
firewall-cmd --permanent --zone public --add-service rpc-bind
firewall-cmd --permanent --zone public --add-service nfs
firewall-cmd --reload