No shell scripting is required.
The RHCE study guide at http://www.redhat.com/training/rhce/examprep.html
"For each of these services, RHCEs must be able to:
Configure host-based and user-based security for the service"
IPtables would fall into this category, as would TCP Wrappers and individual config files for the services. On the exam it's the result that counts - it's your choice which tool to use. For example, you could use IPtables or TCP Wrappers to control access to Telnet. Either would be equally acceptable.
BTW - if you decide to use TCP Wrappers, disable IPtables. Let's say you have decided to use TCP Wrappers for security and you have IPTables running but only configured to the default (services allowed out but not in). This could happen after a default install, for example. If the services are blocked because of this and the Redat grading server can not access the service (which is hapilly running on your server but not accessible behind firewall rules) you get no credit for the task.
Hope this helps