Centos – HTTP through a proxy server is not allowed

Your best option is to get a second IP for the server, set it up as an IP alias. The first IP is set on network interface eth0, the next one on eth0:0 (a third would be eth0:1, and so on).

Here's a general guide, but it might be easier to look for recent instructions for your Linux distro specifically:

http://www.cyberciti.biz/faq/linux-creating-or-adding-new-network-alias-to-a-network-card-nic/

Once you've done that, you set Apache up to bind to the first IP (as it is now) and Tomcat to bind to the new IP, e.g.

eth0   - 192.168.0.1 - Apache
eth0:0 - 192.168.0.2 - Tomcat

Then set your DNS up something like:

example.org        - 192.168.0.1
tomcat.example.org - 192.168.0.2

No need to use :8080 at all, or any redirection/IP Tables forwarding. The links just point to http://tomcat.example.org/whatever/

Note that it is a new network interface, so you will want to check your IPTables rules and:

a) Close port 8080 on your first interface when you are no longer using it

b) Make sure you check / set IPTables to lock down the new IP address so only port 80 is allowed in.

i.e. no combination Tomcat+Apache

This is not true because netstat -anp | grep :80 returned :

tcp 0 0 0.0.0.0:80 0.0.0.0:* LISTEN 3827/httpd

You can shut it down if you want Tomcat be your main Web Server.

Then run your iptables prerouting rule :

sudo /sbin/iptables -t nat -I PREROUTING -p tcp --dport 80 -j REDIRECT --to-port 8088

And it should work.