Hi Roshan,
Did you write the exported path in the /etc/exports file?
the /etc/exports file specifies the exported directory and the hosts permitted to access it, as in the following example:
/exported/directory yourhost.yourdomain.com (or you can write the ip of the host that you are trying to mount the nfs)
Another example /etc/exports file:
/another/exported/directory 192.168.0.3(rw,sync)
Read this article for further info:
https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/5/html/Deployment_Guide/s1-nfs-server-config-exports.html