Compex Technologies NetPassage 18A - Manual (Page 86)

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When NAT is enabled, your LAN is not accessible to the WAN. However,
implementing virtual servers allows you to host Internet servers such as
web servers, FTP servers or Mail servers on your LAN, in spite of NAT.
To Setup a De-Militarised Zone Host
If NAT is enabled, a request from the client within the private network
first goes to the access point. Upon receiving a request, the access
point keeps track of which client is using which port number. Any reply
from Internet goes to the access point first, the access point (from the
port number in the reply packet) knows to which client to forward the
reply. If the access point does not recognize the port number, it will
discard the reply.
When using DMZ on a PC, any reply not recognized by the access point
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.