I've added the CentOS 6 Updates yum repository to my RHEL 6.4 machine. That's because RHEL doesn't ship with the php-snmp package - and the easiest one to find is on the CentOS site. Anyways, this appears to work okay in my environment - no problems I see.
My questions are if this is an acceptable practice - keeping the original RHEL yum repositories active and adding the CentOS to the mix? What problems, if any, should I look out for? Is there a way I can guarantee that the RHEL yum repositories are searched first (and CentOS last)?