When doing nfs through a router:

- check that rpcinfo -p nfshost returns the expected full list of
  processes and ports

- make sure the router is passing all the packets (it probabaly is if
  you are able to normally surf the internet).

- make sure that /etc/exports on the nfs server has the ip address of
  the router since machines behind the router appear to have the
  router's ip address

- In my limited experience exportfs -r did not refresh export
  permissions. I simply restarted nfs with /etc/init.d/nfs restart




From:
http://nfs.sourceforge.net/nfs-howto/ar01s04.html

Use hard,intr and do not use soft.



From: 
http://www.linuxquestions.org/questions/showthread.php?t=497784

Problem: Huge delays for any access to nfs-mounted /home under FC6,
but it works find under FC4 and FC5.

Solution:

Skellert says, " The file server on which I was mounting /home also
has a shorewall firewall running. I've had to statically map the NFS
ports using an /etc/sysconfig/nfs file defining the static port
numbers, as referenced from /etc/init.d/nfs* "

Thanks, Skellert.

After forcing nfs to use static (predetermined) ports by editing
/etc/sysconfig/nfs, just punch the static nfs port through the
firewall. See my notes elsewhere about iptables, but "punch through"
is to allow connections on that port by adding a firewall rule.

Normally, nfs will dynamically create ports within some range, so
without making the ports static, the firewall would have to leave a
range of ports open.