Why mount command fails on RHEL 6.3 whereas it runs successfully on RHEL 6.2?

Issue

• While trying to mount NFS shares using UDP, mount command fails.

[root@nfsclient /]# mount -t nfs -vv srvrhost:/NFS/global/software /trs/global/software
mount.nfs: timeout set for Mon Feb 25 08:59:56 2013
mount.nfs: trying text-based options 'addr=172.21.136.251'
mount.nfs: prog 100003, trying vers=3, prot=6
mount.nfs: trying 172.21.136.251 prog 100003 vers 3 prot TCP port 2049
mount.nfs: prog 100005, trying vers=3, prot=17
mount.nfs: portmap query retrying: RPC: Timed out
mount.nfs: prog 100005, trying vers=3, prot=6
mount.nfs: portmap query failed: RPC: Program not registered
mount.nfs: prog 100003, trying vers=2, prot=6
mount.nfs: trying 172.21.136.251 prog 100003 vers 2 prot TCP port 2049
mount.nfs: prog 100005, trying vers=1, prot=17
mount.nfs: portmap query retrying: RPC: Timed out
mount.nfs: prog 100005, trying vers=1, prot=6
mount.nfs: portmap query failed: RPC: Program not registered
mount.nfs: prog 100003, trying vers=2, prot=6
mount.nfs: trying 172.21.136.251 prog 100003 vers 2 prot TCP port 2049
mount.nfs: prog 100005, trying vers=2, prot=17
mount.nfs: portmap query retrying: RPC: Timed out
mount.nfs: prog 100005, trying vers=2, prot=6
mount.nfs: portmap query failed: RPC: Program not registered
mount.nfs: requested NFS version or transport protocol is not supported