Firewall scenarios

[smiley bob]

I feel im a little confused on this subject.

Say I have two machines behind a firewall.
I understand that theory.
But what if I have this scenario.

Email / Web server
2 user machines.

My understanding is that the Email / web server cannot be behind the firewall.
It must stay public for all to access correct?

So basically I'd like to know...
IF you use web / email servers are those always infront of the firewall?
Do firewalls just defend client machines?

Thanks you

 

[DJ-CHRIS1]

The email / web server could be behind the firewall, however you would need to port forward the correct ports. You'd find this kinda setup in very small businesses and home networks.

A more common setup would be the use of a DMZ which is basically a separate network for devices that need to be visible over the internet. You'd have a router with 3 network interfaces, your standard LAN which would have no ports / services visible over the internet, and your DMZ which would have ports open to the internet, and on some routers this interface could have many IP addresses for each server.

Than sometimes you do have servers directly connected to the internet, or behind transparent firewalls.