mounting permission denied

Hello,

I have a server powered by RedHat Linux 6.2

I have configured a couple of diskless clients, for the server.

I want to mount the /usr and /usr/local directories which are in the
/ partition in the server in the diskless clients.
For this I have made the following entires in the "/etc/exports" file
in the server

/       (rw,no_root_squash)
/usr    (rw,no_root_squash)
/usr/local	(rw,no_root_squash)


Now after booting the Diskless clients, the following error message
appears :-

mount: <IP>:/usr failed, reason given by server, Permission denied

rpcinfo -p shows all required services are running.

How to get the /usr mounted in the diskless clients.

Please help.

Thanks in advance
Johnson.