Problem nfs export, on Red Hat client not preserve file access permissions

My Isilon administrator created me a resource for linux (NFS Export).

When mounting it on a Red Had 5.8 and 6.9 client, I observe the following behavior in file or folder access permissions:

#cat /etc/mtab

142.204.7.24:/ifs/data/w_prueba /prueba3 nfs rw,intr,nolock,bg,hard,rsize=32768,wsize=32768,tcp,retrans=0,addr=142.204.7.24 0 0

#cd /prueba3

#mkdir testDIR

#ls -lad testDIR

drwxrwxr-x 2 314247 CC_HR_DISENO 0 Jul 24 18:34 testDIR/

#chmod 770 testDIR

drwxrwxr-x 2 314247 CC_HR_DISENO 0 Jul 24 18:34 testDIR/

#chmod 700 testDIR -v 

mode of `testDIR/' changed to 0700 (rwx------)

#ls -lad testDIR

drwxrwxr-x 2 314247 CC_HR_DISENO 0 Jul 24 18:34 testDIR/

 

As you can see the permissions are not changed no matter what I do with the chmod command.

But if I do this on the local disk (/ tmp for example) the system respects the changes that I apply with the chmod command. This makes me dismiss a problem with the client's operating system and I think the problem is in the NAS server (Isilon).

Any idea what it could be?