Network Newbie

It might help to know what model of firewall/router solution you are using, but here's a general (if somewhat simplistic) overview. Your firewall is probably using a filtering method called NAT (network address translation). This is the first basic level of protection offered by most firewalls. It receives TCP/IP protocol communications internally on your network from your workstations (which use, I assume, private IP addresses) and forwards them out to the Internet using it's own public IP address. The returning packets are then filtered through the firewall and forwarded back to the appropriate internal IP address so that they reach the originating workstation.

The firewall needs a way, however, to also handle incoming packets that originate outside (IOW, they aren't responding to a request that originated at an internal workstation), such as mail traffic (SMTP +/or POP3), requests coming to a web server behind the firewall (if you have one), etc. This is probably what yourrouter is referring to as a "virtual server." Of course, one way of handling them is to drop all of them, which effectively closes your network off from ALL Internet communications except those that originate within your organization. This is what happens if you don't set up any virtual servers behind your firewall. However, if you want to be able to receive some type of Internet communications that originate outside your network, you would need to designate a certain internal (private) IP address to receive all of the packets coming in on a particular port.

This question was closed by the author