More information for EPEL, please check follow:
https://fedoraproject.org/wiki/EPEL

Follow install step in my RHEL7:
1. Download EPEL RPM

[root@frank yum.repos.d]# wget http://dl.fedoraproject.org/pub/epel/7/x86_64/e/epel-release-7-2.noarch.rpm
--2014-10-01 00:27:11--  http://dl.fedoraproject.org/pub/epel/7/x86_64/e/epel-release-7-2.noarch.rpm
Resolving dl.fedoraproject.org (dl.fedoraproject.org)... 209.132.181.24, 209.132.181.23, 209.132.181.25, ...
Connecting to dl.fedoraproject.org (dl.fedoraproject.org)|209.132.181.24|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 13104 (13K) [application/x-rpm]
Saving to: pel-release-7-2.noarch.rpm

100%[==================================================================================================================>] 13,104      --.-K/s   in 0.1s    

Last-modified header invalid -- time-stamp ignored.
2014-10-01 00:27:12 (109 KB/s) - pel-release-7-2.noarch.rpmsaved [13104/13104]

2. Install RPM

[root@frank yum.repos.d]# rpm -ivh epel-release-7-2.noarch.rpm
warning: epel-release-7-2.noarch.rpm: Header V3 RSA/SHA256 Signature, key ID 352c64e5: NOKEY
Preparing...                          ################################# [100%]
Updating / installing...
   1:epel-release-7-2                 ################################# [100%]
[root@frank yum.repos.d]# 
[root@frank yum.repos.d]# ll
total 44
-rw-r--r--. 1 root root 13104 Oct  1 00:27 epel-release-7-2.noarch.rpm
-rw-r--r--. 1 root root   957 Sep  2 12:14 epel.repo  <<<
-rw-r--r--. 1 root root  1056 Sep  2 12:14 epel-testing.repo  <<<
-rw-r--r--. 1 root root    76 Sep 28 02:25 frank.repo

3. After verify EPEL, found follow alarm:

[root@frank yum.repos.d]# yum repolist
Loaded plugins: fastestmirror, langpacks

frank-repo

 One of the configured repositories failed (Unknown),
 and yum doesn't have enough cached data to continue. At this point the only
 safe thing yum can do is fail. There are a few ways to work "fix" this:

     1. Contact the upstream for the repository and get them to fix the problem.

     2. Reconfigure the baseurl/etc. for the repository, to point to a working
        upstream. This is most often useful if you are using a newer
        distribution release than is supported by the repository (and the
        packages for the previous distribution release still work).

     3. Disable the repository, so yum won't use it by default. Yum will then
        just ignore the repository until you permanently enable it again or use
        --enablerepo for temporary usage:

            yum-config-manager --disable 

     4. Configure the failing repository to be skipped, if it is unavailable.
        Note that yum will try to contact the repo. when it runs most commands,
        so will have to try and fail each time (and thus. yum will be be much
        slower). If it is a very temporary problem though, this is often a nice
        compromise:

            yum-config-manager --save --setopt=.skip_if_unavailable=true

Cannot retrieve metalink for repository: epel/x86_64. Please verify its path and try again

4. Edit EPEL.repo and workaround it
Remove not enable repo
Use baseurl, not mirrorlist, that should root reason.
Set priority is 10, CD repo’s priority is 1

[root@frank yum.repos.d]# vim epel.repo 
[epel-debuginfo]
name=Extra Packages for Enterprise Linux 7 - $basearch - Debug
#baseurl=http://download.fedoraproject.org/pub/epel/7/$basearch/debug
mirrorlist=https://mirrors.fedoraproject.org/metalink?repo=epel-debug-7&arch=$basearch
failovermethod=priority
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-7
gpgcheck=1

[epel-source]
name=Extra Packages for Enterprise Linux 7 - $basearch - Source
#baseurl=http://download.fedoraproject.org/pub/epel/7/SRPMS
mirrorlist=https://mirrors.fedoraproject.org/metalink?repo=epel-source-7&arch=$basearch
failovermethod=priority
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-7
[epel]
name=Extra Packages for Enterprise Linux 7 - $basearch
baseurl=http://download.fedoraproject.org/pub/epel/7/$basearch
#mirrorlist=https://mirrors.fedoraproject.org/metalink?repo=epel-7&arch=$basearch
priority=10
enabled=1
gpgcheck=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-7

5. Verify again:

[root@frank yum.repos.d]# yum clean all
Loaded plugins: langpacks
Cleaning repos: epel frank-repo
Cleaning up everything
[root@frank yum.repos.d]# 
[root@frank yum.repos.d]# yum makecache
Loaded plugins: langpacks
epel                                      | 4.4 kB  00:00:00     
frank-repo                                | 4.1 kB  00:00:00     
(1/8): epel/x86_64/filelists_db           | 4.7 MB  00:00:02     
(2/8): epel/x86_64/group_gz               | 250 kB  00:00:03     
(3/8): frank-repo/group_gz                | 134 kB  00:00:00     
(4/8): frank-repo/filelists_db            | 3.0 MB  00:00:00     
(5/8): frank-repo/primary_db              | 3.4 MB  00:00:00     
(6/8): frank-repo/other_db                | 1.3 MB  00:00:00     
(7/8): epel/x86_64/primary_db             | 3.3 MB  00:00:05     
(8/8): epel/x86_64/other_db               | 1.6 MB  00:00:05     
(1/2): epel/x86_64/updateinfo             |  33 kB  00:00:02     
(2/2): epel/x86_64/pkgtags                | 1.2 MB  00:00:04     
Metadata Cache Created
[root@frank yum.repos.d]# yum repolist 
Loaded plugins: langpacks
repo id                                                  repo name                                                                                    status
epel/x86_64                                              Extra Packages for Enterprise Linux 7 - x86_64                                               5,921
frank-repo                                               rhel7 repo