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HOWTO: Configure NFS for control by firewalls and IPTABLES

In any modern enterprise environment, security is a major issue. NFS and Linux/Unix have a long history together, but back then, security was that big a deal. Admins were few and servers too. So you know how dunnit.
These days, when you configure NFS, security is important. So a local firewall on a server is no luxury. However, NFS uses several other daemons to do its duty and among these is RPC. RPC uses a random port numner in the high ranges, so you must first fix these to a static port (of your choice). Lowth.com has detailed instructions on the how and where, as well as a handy iptables firewall configurator wizard you can use in your browser. Red Hat has their own knowledgebase entry on the subject...

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