WESM zl Management and Configuration Guide WT.01.XX and greater

8-8
Configuring Network Address Translation (NAT)
Overview
In fact, instead of configuring dynamic source NAT to conceal private
addresses, you might want to configure only destination NAT. The Wireless
Edge Services zl Module automatically performs source NAT on the traffic
returning from the server.
Port Address Translation for Dynamic NAT
To enable multiple users to share one IP address, the Wireless Edge Services
zl Module uses port address translation in conjunction with NAT. When the
module translates a local IP address to a global address, it assigns each local
address a unique port number, as shown in Table 8-1.
The Wireless Edge Services zl Module uses this port number to forward return
traffic, which is destined to the single global IP address, to the correct local
IP address. For example, Table 8-1 lists possible IP address for the network
shown in Figure 8-3. In this case, the module translates all inside addresses
(in the 192.168.1.0/24 subnetwork) to 10.1.1.1. If a packet arrives for 10.1.1.1
on port 4001, the module knows to forward the packet toward the station at
192.168.1.11.
Table 8-1. Information Recorded in a Port-Mapping Table for a Sample Network
Static, or One-to-One, NAT
You can also configure static definitions for NAT. In this case, you manually
specify the following information for each one-to-one NAT:
■ the IP address (and optionally, port) that should be translated
■ the IP address (and optionally, port) that should replace the original
address
The Wireless Edge Services zl Module can perform static translation on both
source IP addresses and destination IP addresses. In addition, it can apply
NAT to traffic inbound from the inside network or from the outside network.
Local IP Address Translated (Global)
IP Address
Translated Port Destination IP Address Destination Port
192.168.1.10 10.1.1.1 4000 10.20.1.1 80
192.168.1.11 10.1.1.1 4001 172.16.1.10 80
192.168.1.12 10.1.1.1 4002 172.16.10.5 80
192.168.1.13 10.1.1.1 4003 10.45.16.1 80
192.168.1.14 10.1.1.1 4004 172.16.11.1 80