Compex Technologies NP25G 6C - Manual (Page 63)

Page 58
Configure Virtual Server Based on DMZ Host
When NAT is enabled, an Internet request from a client within the
private network first goes to the router. Upon receiving a request, the
router keeps track of which client is using which port number. Since any
reply from Internet goes to the router first, the router (from the port
number in the reply packet) knows to which client to forward the reply.
If the router does not recognize the port number, it will discard the
reply.
When using DMZ on a PC, any reply not recognized by the router will
be forwarded to the DMZ-enabled PC instead.
You may wish to set up a DMZ host if you intend to use a special-
purpose Internet Service such as an online game for which no port
range information is available. You can also host Web pages or public
information that can be served to the outside world, on the DMZ host.