Isolated YUM svr farming out RHEL7, 6, and CentOS 7 packages

Is is possible to have an isolated RHEL7 Yum server (not connected to the intrawebs) to be able to supply updates for RHEL6 and CentOS7 in an isolated network (LAB) environment?

Someone requires an appliance that runs RHEL6 and another that has CentOS7 and I need to keep them patched for security.

If so - where may I find an article or documentation describing how to set up this effery"..

I have always found answers to my questions here - but I haven't found this particular question!

Thanks in Advance

LAChicaRita