Hello Mathew,
Yes, if your NFS server is behind the firewall, you need to open some ports to allow the client to connect to the server. Here are the ports that need to be opened:
-TCP port 2049: The default port of NFS server listening.
UDP port 2049: The default port of NFS server listening.
-TCP/UDP port 111: RPC binding port is used to establish connections between clients and servers.
Thanks,
Shujun