Configuring Servers Behind Port Forwarding (Example); Port Translation; Figure 141 Multiple Servers Behind Nat Example - ZyXEL Communications ZyWALL 5 User Manual

Table 96 Services and Port Numbers
SERVICES
SNMP trap
PPTP (Point-to-Point Tunneling Protocol)

17.5.3 Configuring Servers Behind Port Forwarding (Example)

Let's say you want to assign ports 21-25 to one FTP, Telnet and SMTP server (A in the
example), port 80 to another (B in the example) and assign a default server IP address of
192.168.1.35 to a third (C in the example). You assign the LAN IP addresses and the ISP
assigns the WAN IP address. The NAT network appears as a single host on the Internet.

Figure 141 Multiple Servers Behind NAT Example

17.5.4 Port Translation

The ZyWALL can translate the destination port number or a range of port numbers of packets
coming from the WAN to another destination port number or range of port numbers on the
LAN (or DMZ). When you use port forwarding without port translation, a single server on the
LAN or DMZ can use a specific port number and be accessible to the outside world through a
single WAN IP address. When you use port translation with port forwarding, multiple servers
on the LAN or DMZ can use the same port number and still be accessible to the outside world
through a single WAN IP address.
The following example has two web servers on a LAN. Server A uses IP address 192.168.1.33
and server B uses 192.168.1.34. Both servers use port 80. The letters a.b.c.d represent the
WAN port's IP address. The ZyWALL translates port 8080 of traffic received on the WAN
port (IP address a.b.c.d) to port 80 and sends it to server A (IP address 192.168.1.33). The
ZyWALL also translates port 8100 of traffic received on the WAN port (also IP address
a.b.c.d) to port 80, but sends it to server B (IP address 192.168.1.34).
Note: In this example, anyone wanting to access server A from the Internet must use
port 8080. Anyone wanting to access server B from the Internet must use port
8100.
Chapter 17 Network Address Translation (NAT)
ZyWALL 5 User's Guide
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