i have RHEL 6.3

[root@RHEL6 yum.repos.d]# uname -a
Linux RHEL6.3-64-BuildMac 2.6.32-279.el6.x86_64 #1 SMP Wed Jun 13 18:24:36 EDT 2012     x86_64 x86_64 x86_64 GNU/Linux

My /etc/yum.conf looks like  
[main]  
cachedir=/var/cache/yum/$basearch/$releasever  
keepcache=0  
debuglevel=2  
logfile=/var/log/yum.log  
exactarch=1  
obsoletes=1  
gpgcheck=1  
plugins=1  
installonly_limit=3  
reposdir=/etc/yum.repos.d/rhel.repo

The contents of my /etc.yum.repo.d/rhel.repo looks like
[rhelrepo]  
name=my rhel repo  
baseurl=http://mirror.centos.org/centos/6.3/os/x86_64/  
#gpgkey=http://mirror.centos.org/centos/6.3/os/x86_64/RPM-GPG-KEY-CentOS-6  
enabled=1  
gpgcheck=0  

But my yum update fails with the following error

[root@RHEL6 yum.repos.d]# yum update  
Loaded plugins: product-id, security, subscription-manager
Updating certificate-based repositories.
Unable to read consumer identity
Setting up Update Process
No Packages marked for Update

please could somebody help