Newer versions of RedHat do not carry the FireHOL packages because there is no packager. If you want to help that effort, these links might help:
As a result we make a best-effort attempt to build suitables RPMS, so you can always download the latest.
To install on CentOS 7 / RHEL7:
yum --nogpgcheck localinstall iprange-x.y.z-1.el7.centos.x86_64.rpm
yum --nogpgcheck localinstall firehol-x.y.z-1.el7.centos.noarch.rpm