Looks like just starting the nfs service turns on V2, 3, and 4 (based on reading the script, reading the man pages, and looking at the ports using netstat -l). However, I can connect using -t nfs in the mount, and -t nfs4 fails. I don't believe this is a firewall issue, internal IPs are fully open to each other according to an early rule in iptables. $ sudo mount host03:/home/ddb /mnt/ddb -t nfs4 -o rw,hard,intr mount: permission denied but $ sudo mount host03:/home/ddb /mnt/ddb -t nfs -o rw,hard,intr $ I'm not sure I especially care about NFS V4 (this is to share the programmers' home directories, so it's easy to work on any of the production systems; it won't be particularly high-load or any particularly strange usage pattern), but I care about understanding things at least. Both systems are running Centos 4.6. Any ideas? -- David Dyer-Bennet, dd-b at dd-b.net; http://dd-b.net/ Snapshots: http://dd-b.net/dd-b/SnapshotAlbum/data/ Photos: http://dd-b.net/photography/gallery/ Dragaera: http://dragaera.info