if=/dev/zero of=/swapfile bs=1M count=600 mkswap /swapfile
/etc/fstab:
/swapfile swap swap defaults 0 0 mount -a

see explanation below.
Explanation
* Verify the File whether Shared or not ? : cat /etc/exports
* Start the nfs service: service nfs start
* Start the portmap service: service portmap start
* Make automatically start the nfs service on next reboot: chkconfig nfs on
* Make automatically start the portmap service on next reboot: chkconfig portmap on
* Verify either sharing or not: showmount -e localhost
* Check that default firewall is running on system?
If running flush the iptables using iptables -F and stop the iptables service.