Hello custangro, manoj and bala.linuxtech...
"showmount -a" won't hold true every time, specially in case of NFSv4 since NFSv4 has stopped using rpc.mountd daemon. rpc.mountd is the one which puts in the information regarding the mounts in "/var/lib/nfs/rmtab" (in case of fedora and rhel) and showmount uses "/var/lib/nfs/rmtab" to fetch it's output.
"netstat -an | grep <nfs-server-ip>:2049"
The above netstat command will also not help in this case as the nfs clients which haven't been active for sometime won't be shown in the netstat output.
I am still looking for the alternative for this.. if you guys find anything, do post it here