With RHEL 7, a minimal install doesn't even include an "ifconfig" binary. It's still available as /sbin/ifconfig if you install the "net-tools" package, but it's no longer required and guaranteed to be there.
I've tried both facter 1.7.6 and facter 2.0.2, both from the PuppetLabs repo, and because neither package records a dependency on "net-tools" for RHEL 7, neither version will correctly gather the "interfaces" fact, at least on a system where a minimal install was done.
$ cat /etc/redhat-release
Red Hat Enterprise Linux Server release 7.0 (Maipo)
$ type -a ifconfig
-bash: type: ifconfig: not found
$ facter --version
$ sudo facter | egrep 'interface'
$ sudo yum whatprovides /sbin/ifconfig
net-tools-2.0-0.17.20131004git.el7.x86_64 : Basic networking tools
Repo : rhel-x86_64-server-7
Filename : /sbin/ifconfig
$ sudo yum install net-tools
$ sudo facter | egrep 'interfaces'
interfaces => ens192,ens224,lo
The easy, short-term fix is to update the package so that for RHEL 7, facter also requires that "net-tools" is installed.
Note that I've linked this issue to
FACT-184, since Red Hat has indicated that ifconfig is now deprecated and "ip" should be used instead. In addition, the release notes for RHEL 7 indicate that the output format from ifconfig has changed somewhat, though apparently facter is still able to parse it correctly, as once the net-tools package is installed, the "interfaces" fact is correctly populated.