I deleted the new "/etc/nfs.conf". With
# cat /etc/sysconfig/nfs
RPCNFSDARGS="--udp"
I get
[root@localhost ~]# rpcinfo -p
program vers proto port service
100000 4 tcp 111 portmapper
100000 3 tcp 111 portmapper
100000 2 tcp 111 portmapper
100000 4 udp 111 portmapper
100000 3 udp 111 portmapper
100000 2 udp 111 portmapper
100005 1 udp 20048 mountd
100005 1 tcp 20048 mountd
100005 2 udp 20048 mountd
100005 2 tcp 20048 mountd
100005 3 udp 20048 mountd
100005 3 tcp 20048 mountd
100003 3 tcp 2049 nfs
100003 4 tcp 2049 nfs
100227 3 tcp 2049 nfs_acl
100003 3 udp 2049 nfs
100227 3 udp 2049 nfs_acl
100021 1 udp 58880 nlockmgr
100021 3 udp 58880 nlockmgr
100021 4 udp 58880 nlockmgr
100021 1 tcp 33179 nlockmgr
100021 3 tcp 33179 nlockmgr
100021 4 tcp 33179 nlockmgr
So udp is enabled for nfsv3.
With an empty "/etc/sysconfig/nfs", I get tcp-only:
[root@localhost ~]# rpcinfo -p
program vers proto port service
100000 4 tcp 111 portmapper
100000 3 tcp 111 portmapper
100000 2 tcp 111 portmapper
100000 4 udp 111 portmapper
100000 3 udp 111 portmapper
100000 2 udp 111 portmapper
100005 1 udp 20048 mountd
100005 1 tcp 20048 mountd
100005 2 udp 20048 mountd
100005 2 tcp 20048 mountd
100005 3 udp 20048 mountd
100005 3 tcp 20048 mountd
100003 3 tcp 2049 nfs
100003 4 tcp 2049 nfs
100227 3 tcp 2049 nfs_acl
100021 1 udp 59984 nlockmgr
100021 3 udp 59984 nlockmgr
100021 4 udp 59984 nlockmgr
100021 1 tcp 37015 nlockmgr
100021 3 tcp 37015 nlockmgr
100021 4 tcp 37015 nlockmgr