Not able to register redhat 6

Is REDHAT 6 support available ? I have recently downloaded Reghat 6 and install to my VM but it does not allow #yum uypdate also . It is asking below info

[root@EKBAL-REDHAT6 ~]# yum updates
Loaded plugins: rhnplugin
This system is not registered with RHN.
RHN support will be disabled.

While trying to register by command but it does not allow . Kindly help on this