I have a few C5 machines on an isolated LAN that connect to a RHEL5 server via NFS and NIS for authentication. I discovered that one of the C5 workstations worked fine for NFS exporting, but refused to collaborate with the EL5 server for NIS user authentication. I had successfully connected other systems to this server without issue, but this machine was finicky. I had initially enabled the EL5 firewall, then later disabled it, including selecting --disable-firewall. Still, this one C5 workstation wouldn't cooperate for user authentication. Then, as a bit of an experiment, I opted to visit the EL5 services and manually highlight IPtables, clicked STOP, and tried the verification again. This time, the C5 system got the NIS data. Now, if I want to enable a firewall on all machines - As a server, EL5 does have an option to select NFS services be run on specific ports. How do I configure the C5 clients to also communicate on those ports, thus allowing full NIS/NFS user authentication and directory exporting, all the while with built-in firewall protection on all systems? These are all out-of-box setups, with no updates, and full package installs from the install media. As time goes on, I will migrate to the OpenLDAP world, but I haven't had the opportunity to experiment with that just yet. Thanks. Scott