NFS-Clients (Mac OSX) loose connection to Ubuntus NFS-Kernel-Server

[Ingo Lantschner]

Hello,
I had a really fine working configuration with Ubuntu-Server as  
firewall and NFS-Server for LAN-Clients (Ubuntu, Mac OSX). Pulling  
even very large files from the Ubuntu-server to Mac-Clients worked  
reliable and really fast! Since the Server-version was very old (5.04  
Hoary Hedgehog) and no more updates were available I had to do  
something. Yesterday I reinstalled (no upgrade) the Ubuntu-Server  
(Dapper Drake 6.06 LTS) and added a dedicated firewall - so now the  
NFS-Server is in the DMZ.

Now I can not any longer use the NFS-Shares from the Mac-Clients,  
although I copied the /etc/exports exactly from the old server and  
did not change anything on the clients side.

Mounting the share with "sudo mount -t nfs -o P,3,r16384,w16384 mail:/ 
mnt/daten daten" gives me the mountpoint on the client and I can  
browse the files on the server - but after a short period (seconds)  
the NFS-connection breaks and is no more accessible.

I used and use nfs-kernel-server and export the files using  
"insecure" (needed by OSX).

So there are three questions now:
1. Did anything change in the  NFS-Server from Hoary to Dapper?
2. Could it be, that due to the router/firewall in between these  
troubles occur? (its BSD-based, m0n0wall)
3. How can such NFS-problems tracked down from the serverside - is  
there a "debug"-option in NFS with verbose output to a log?

TIA for any hints - Ingo.

P.S. May be usefull:

ingo at mail:~$ cat /etc/exports
# /etc/exports: the access control list for filesystems which may be  
exported
#               to NFS clients.  See exports(5).
#/backup         192.168.4.0/24(rw,no_root_squash)
/mnt/daten      192.168.4.0/24 
(rw,insecure,all_squash,anonuid=1000,anongid=1000,async)
/mnt/daten/bt   192.168.4.0/24 
(rw,insecure,all_squash,anonuid=1003,anongid=1003,async)


-- 
Ingo Lantschner
Vienna/Austria
Mob (+43-664) 143 84 18