I have been trying to get a sun to boot from nfs and finally got it right.
As far as I can tell there are some errors in both the diskless and exports
manual pages.
For instance I would get an illegal option error when trying to use the
-alldirs option (mentioned in the exports manual page) when starting the
mountd daemon.  The diskless page also gives an example of putting multiple
lines for the same client in the exports file.  This is clearly forbidden
in the exports manual page and indeed I get an error when trying it. I also
tried to specify clients using the network address option as you are doing
but could not get it to work (even after following the manual page)  I
would recommend to make sure you don't get any errors when starting up
mountd. Try mounting the nfs directory from the the host itself (you can
just add a line in /etc/exports as follows      
servername:/export/clientname  -maproot=root   clientname

and then type mountd   and then  mount_nfs servername:/export/clientname  
/mnt
and see if the mount directory is accessible at /mnt.  If you can do this,
you know nfs is properly enabled at least for the host machine itself.

Good luck,

Stephen
----------
> From: Greg Evans <raisplin@rcn.com>
> To: NetBSD List <port-mac68k@netbsd.org>
> Subject: Exporting filesystem??
> Date: Saturday, March 13, 1999 11:38 PM
> 
> Hi gang,
> 
> New questions..
> 
> I am trying to NFS mount a directory on my NetBSD box so that I can 
> install RedHat Linux on another Machine (yeah..don't ask)...
> 
> so far what I have done is
> 
> /etc/exports I added the following line
> 
> /RHLinux -ro -maproot=root -network 192.168.1.0 -mask 255.255.255.0
> 
> this is so that hopefully only machines on my internal network can access

> this directory.
> 
> then I started mountd with /usr/sbin/mountd and then nfsd with 
> /usr/sbin/nfsd -tun 4
> 
> (this is what I saw in the FAQ for Diskless NEtBSD HOW-TO) for starting 
> the correct daemons.
> 
> so now I try to use the Linux installer disks to get to the directory and

> so far it is yet to work.  have I done something wrong?  or do I just not

> know wher eto look in the FAQ for the proper information?
> 
> Regards,
> 
> Greg