Hi Jade,
You have 2 options basically.
- Use port forwarding (TCP level)
- Use a reverse proxy (HTTP level)
Using port forwarding maybe simpler and straigth forward. But it does limit you to the number of external IP addresses. In your case only 5 sites can be up. Since port forwarding is a one to one mapping of IP Addr and ports. I assume that you would like to only access your sites using only the standard HTTP port 80, this will limit you to only 5 sites.
Using a reverse proxy such as Apache + proxy or Squid may give you better results. Although this maybe more complex. Since you will be just be using the HTTP headers you can have infinite amount of internal web servers with only 1 IP address. You may also want to turn on caching for some of your sites.
On both cases you have to use NAT or masquarading so the internal web servers can access the outside world. Maybe you can also use NAT or MASQ in reverse to let the external network access your internal network. Not too sure if its possible because normally I use NAT or MASQ from inside going outside.
