Well, i have ONE external static ip and two computers connected to a router.
Computer 1 have ip 192.168.0.1
Computer 2 have ip 192.168.0.2

Both have apache installed. On modem i made a nat on port 80 to 192.168.0.1. But now, i would like that everytime that someone try to access /webmail on my server it passes to 192.168.0.2.
How can i do this?

Another thing. Is it possible to make those two computers respond as the same server? I mean, some kind of balance, because the first computer sometimes have to throw something into swap (when there are lots of php running). So things get a little slow.

I read something about changing something in the dns server like

www1 IN A first_server_ip
www2 IN A second_server_ip

But how could i do this if i only have one external static ip?

is it possible?
can somebody answer it to me?

To accomplish sending users off to the other machine, you can try using redirection, based on (internal) IP address (or use 2 hostnames, so you can be sure to reach the right machine). See also http://httpd.apache.org/docs/trunk/urlmapping.html.

For the second question, you need load balancing. I'm not very experienced in that. Maybe Apache's flood tool can help you. However, combining this with the redirection may require additional configuration, such as URL rewriting.

Maybe mod_rewrite, as explained on the same webpage, can help you too.

i read the thing on the link you posted but i still can't figure out how am i going to do this.

I know that there is a way to do this, because i thing that heavy-traffic sites like linuxquestions.org aren't running on a single machine.

A few things:

A directory on your server is not any indication of a unique "site"...
http://www.google.com/gmail is the gmail directory on the www.google.com site
http://gmail.google.com is a seperate sub-domain in the google.com domain
(these two URLs happen to take you to the same destination, but that is due to the way they were set up and not an inherent fact of URLs.)

What you read about is probably what is called Round Robin DNS and it's actually:
Either way, this can't be done with only one "public" IP address.

The ways I can think of to solve your dilema include:
-Set up redirection of port 80 to one webserver and another port to the other webserver.
-Set up an alias on one webserver that points to the other one (that's in the link timmeke posted) so that something like www.thisdomain.com/thatdirectory aliases to the other server
-Set up two domain names that resolve to the same IP and get your external facing firewall to do host based routing (I've never done this, I just understand the concept and I'd bet something could be added to iptables/netfilter to get it to do this)
-Buy a hardware based load balancing solution ($$$).

What kind of hardware are you talking about?

Professional, heavy duty sites often use specific hardware for load balancing.
ie they have multiple machines attached to a specific piece of hardware that sends the
requests to one of the machines, distributing the load in the process.

A quick Google search turned up:
http://searchnetworking.techtarget.c...005407,00.html

Or you could go for something like a High Availability type solution. These solutions typically provide load balancing of IP addresses. I think there are modules that work specifically for Apache.

Have a look at the heartbeat product. Go to www linux-ha org (put the dots where they need to be)

There might be some tools to help you.

Something like
http://www.juniper.net/products/integrated/ns_5000.html