User's Guide

3e-531AP Wireless Access Point
Chapter 4 Gateway Con guration
56
29000125-001 C
Virtual Server
In order to protect the
Private Network, the built-in
NAT  rewall
 lters out traf c to the private network. Since all clients on the Pri vate
Net work are normally not visible to outside users, the virtual server func-
tion allows some clients on the Private Net work to be ac cess ed by outside
users by con guring the application mapping func tion offered on this
page. Certain well known ap pli ca tions use speci c TCP ports, such as
Telnet (port 23),
FTP (port 21), and
Web server (port 80). Client com put ers
on the Private LAN can host these ap pli ca tions, and allow users from the
Internet to access these ap pli ca tions hosted on the virtual servers.
This is done by mapping virtual servers to private IP addresses,
according to the speci c TCP port application. As the planning table
below shows, we have identi ed a
Telnet (port 23) virtual server for
pri vate IP 192.168.15.56, a
SMTP Mail (port 25) virtual server for pri-
vate IP 192.168.15.33, and a Web (port 80) virtual server for private IP
192.168.15.64. For example, all
Internet requests to the gateway for SMTP
Mail services (port 25) to the WAN IP address will redirected to the Pri-
vate Network computer speci ed by the server IP 192.168.15.33.
Service Port
Server IP
23
192.168.15.56
25
192.168.15.33
80
192.168.15.64
We recommend that IP addresses of
virtual server computers hosted
on the Private Network be manually (statically) assigned to coincide with
a static server mapping to that speci c IP address. Virtual servers should
not rely on the dynamic IP assignment of the DHCP server function
which could create unmapped IP address assignments.
Protocol
– Selection of either
UDP
,
TCP
, or
Both
(TCP and UDP) al-
lows these speci ed network protocols to pass through during the TCP
port communication with each virtual server IP address.