NFS help needed

[Michael George]

I'm having some trouble with NFS and I'm at a loss to figure out what 
the problem is.  Unfortunately, there are several variables, but 
luckily I have 3 servers so I can test many scenarios to rule out 
issues...

I have a new YDL server running on an Xserve with YDL2.3.  All updates 
are installed and the kernel only supports NFS2 from what I can tell.  
This is the problem server.  We'll call it System A.

I have a RHL7.1 server running on a Compaq which is fairly up to date.  
We'll call it System B.

On the other end of a VPN is a RHL7.2 server running on an AMD-based 
system.  We'll call it System C.

The problem is that when I mount a filesystem from A to C, I get 
success on the mount but failure when I try to "ls" the filesystem.  
There only anomalous message in /var/log/messages is "kernel: svc: 
unknown version (3)", presumably because the client was using NFS3 
rather than NFS2.

However, when I mount a fs from A to B, I get the same error and I get 
success.  Also, if I set nfsvers=2 in system C's /etc/fstab, I don't 
get the svc error, but the "ls" still times out.

Thus, v2 vs. v3 doesn't seem to be the issue.

Next suspect: the VPN.  However, I can mount from B to C and from C to 
B and there are no problems whatsoever.  BUT, perhaps the NFSv2 through 
the VPN is the culprit.

I also have restrictions on what networks can connect to each server, 
but I have it set to 192.168.0.0/255.255.0.0 on all servers, so that I 
can mount from either end of the VPN.

I will stop now so as to not overwhelm the list with perhaps needless 
details.  If anyone might know what the issue would be, I'd appreciate 
a note.  I have rebuilt the kernel on System A to use NFSv3, but being 
on the other end of a VPN (and 120mi. away), I will not be rebooting to 
that kernel until Wednesday when I'm in the office again.

Thanks!

-Michael