IPtables-config, connection tracking modules

Hi all

Here I am jamming away with my RHCE study, and I have come across a bit of inconsistency among the various resources I am using.

When configuring IPtables for the different network services, some resources have a step whereby they instruct you to edit /etc/sysconfig/iptables-config and append some connection tracking modules to the IPTABLES_MODULES="" parameter.

The comments in iptables-config say that I can find more information in /etc/modprobe.conf only that doesn't exist. Wiki is more useful and tells me that these are plugin modules that give application-layer knowledge about connections i.e. if two connection are related or not.

That's great and all but it's still pretty much Greek to me unfortunately. Then of course there is the fact that some of the resources I am using don't mention these conntrack modules at all.

So I guess my questions are:

• should I just calm down, this isn't relevant for RHCE anyway?
• can anyone give it to me straight?
• What are these iptables modules?
• What is their purpose?
• Are they necessary?
• Are they legacy?
• What is a typical use case for these modules?

Pretty much if anyone could help me on the path of delivering me from ignorance... that'd be great :D