[Puppet Users] How to refer to common variables across multiple modules?

We need to refer to common variables across multiple modules. For example,
our dns module, firewall module and monitoring module need knowledge of our
radius server IP address. Is the correct approach to create a 'common'
class where these variables are defined and then reference them from each
module and create a class dependancy as below. We are using a custom ENC
which outputs the class parameters.

# modules/common/manifest/init.ppclass common (
   $radius_ip,
   $fw_ip,
   $zabbix_ip,) {}
# modules/common/manifest/apache.ppclass apache (
   $fw_ip = $common::fw_ip,
   $zabbix_ip =$common::zabbix_ip,) {
   class { 'common': } ->
   class { 'apache': }}
# modules/common/manifest/maradns.ppclass maradns (
   $radius_ip = $common::radius_ip,
   $fw_ip = $common::vpn_ip,){
   class { 'common': } ->
   class { 'apache': }}
# ENC ouput---
classes:
     common:
       fw_ip: '10.50.1.1'
       radius_ip: '10.50.1.12'
       zabbix_ip: '10.50.1.11'
     apache:
     ntp:
     maradns:
environment: production