Installing 2.6 enterprise on RHEL6.6 following instructions here http://docs.mongodb.org/v2.6/tutorial/install-mongodb-enterprise-on-red-hat/ for the 2.6 repo gave me a 404 from yum

https://repo.mongodb.com/yum/redhat/%24releasever/mongodb-enterprise/2.6/x86_64/repodata/repomd.xml: [Errno 14] PYCURL ERROR 22 - "The requested URL returned error: 404 Not Found"

I used the workaround and replaced "$releasever" with "6" as they are on RHEL 6.6 and it installed successfully.