Why does df command not show all the mounted network shares in Red Hat Enterprise Linux 7?

Issue

• NFS/CIFS mounts on clients don't appear in df output.

• There are 2 NFS mounts mounted but only one is showing in df command:

# df 
Filesystem                          1K-blocks      Used Available Use% Mounted on
node1:/vol/vol1  681574400 571282752 110291648  84% /vol1

# df -t nfs -a
Filesystem                           1K-blocks      Used Available Use% Mounted on
node1:/vol/vol1  681574400 571282752 110291648  84% /vol1
node1:/vol/vol2 681574400 571282816 110291584  84%  /vol2