So apparently you want to set this box up to be a:
[INDENT]router
webserver
mail server[/INDENT]
Although all these things can be done on the one machine, I personally would consider it a bit of security risk.
Moving on, I have not had the opportunity to setup a linux based mail server as of yet, but I did a bit of research in preparation to set one up. The same goes for the router.
I have setup a web server though (Apache), but I think the first thing that needs to be looked at is/are your network connection(s). Without those working, doing anything else would be a waste.
As stated in your post, you have two NICs in the box. I suppose you would want to connect each one to a separate network, i.e., WAN (Internet) and LAN (local machines).
I am a command line type of person so if you want to use a gui interface for this stuff you'll have to do the research to figure out what tools your distro provides.
Anyway...open a terminal in X or login to console and type in
ifconfig -a
Depending on what kind of setup you've got, e.g., VPN Tunnel, multiple NICs, fiber channel, etc., it may display lots of interfaces. For our purposes here, we are only going to be interested in ethernet devices.
In the output in the terminal, look for anything that saysethx, x being a number from one to whatever corresponding to each ethernet interface. These will be your ethernet cards. Since you said that you have two NICs in the system, you should have least two of these entries listed. Now each of these devices must be configured.
If you plan on making this box a server it would be wise, in my opinion, to assign static IP Addresses. This can be done by typing in
ifconfig <em><interface></em> <em><ip_address></em> netmask <em><netmask></em>
Replace with ethx (corresponding to you first interface, probably eth0), with the ip address you want to assign for either the LAN or WAN connection, and with the network mask that matches the ip given. Now do the same for the other interface. Type in
ifconfig -a
again and analyze the output for any mistakes and typos.
When it's all good, type in
ifconfig <em><interface></em> up
This shouldbring up (read:activate) the interface that was specified. When you get this far, the mail/webserver/router functionality can then be setup.
I won't write anymore because by this point most prople would have fallen asleep.
PS Post back if there is/are no ethernet device(s) listed in the
ifconfig -a
output. That will require that someother things be done prior to the TCP/IP config for the interfaces being touched.
