EX200 and EX300 are currently based on Red Hat Enterprise Linux 6. (RHEL 6)
While RHEL 6 is based on some elements of both Fedora 12 and 13, the best "free" option for training purposes is a distribution that uses the same source code. Red Hat releases the RHEL 6 source code under the GPL. Several groups have compiled that source code (without Red Hat trademarks) into distributions such as Scientific Linux 6 and CentOS 6.
I believe Scientific Linux 6 and CentOS 6 are better than any Fedora release for candidates who are studying for their RHCSA and/or RHCE certs.
I describe this and more in my book, http://www.amazon.com/RHCSA-Linux-Ce...dp/0071765654/
. With the permission of and guidance from the people behind LQ, I've highlighted some of the key points in excerpts on this sub-forum.