Kerberos + NFSv3 on RHEL6.1

[Vipin Rathor]

Hello People,
I'm trying to configure NFS (v3) server with Kerberos on RHEL6.1. I'm
using RHEL5.5 as NFS client. When I try to mount from client, I'm
getting 'Invalid argument' error (return code:32/broken pipe). I tried
to run rpc.gssd & rpc.svcgssd in debug mode, but not much helpful. I'm
not seeing any GSS-API traffic during mount request.

Questions:
1. Is NFS server (running on RHEL6.1) certified with NFS client on RHEL5.5 ?
2. What is the support matrix for NFS server on RHEL6.1 ?
3. Do I need any special configuration setting to make this setup working?

Here's the info about the packages + system that I'm using:
NFS server:
 - RHEL 6.1 (2.6.32-131.12.1.el6.x86_64 )
 - nfs-utils-1.2.3-7.el6.x86_64
 - krb5-libs-1.9-9.el6.i686

NFS client
- RHEL 5.4 (2.6.18-164.el5)
- nfs-utils-1.0.9-42.el5
- krb5-libs-1.6.1-36.el5

Thanks in advance.

-- 
-Rathor