Wireless/Redundant Edge Services xl Module Management and Configuration Guide WS.02.xx and greater

8-12
Configuring Network Address Translation (NAT)
Overview
Static NAT on Source Addresses
Static source NAT is an alternative to dynamic source NAT. However, instead
of allowing many stations to share one global address, static source NAT sets
up a one-to-one correspondence between a particular IP address and a trans-
lated IP address. Use this option only when relatively few devices in one
network (inside or outside) need to access devices in the other network.
Understanding Local and Global Addresses
When you configure NAT on the Wireless Edge Services xl Module, you define
a local address and a global address. As mentioned earlier, the local address
is the pre-translation address. For source NAT, the local address is always the
IP address assigned to the device for the network in which the device resides.
In Figure 8-6, the local address is any address used by a device in WLAN A—
the 10.1.1.0/24 subnetwork.
Figure 8-6. Local Addresses
However, for destination NAT, the local address is actually the address as it
appears across the border between inside and outside. This is because pack-
ets, pre-translation, are destined to the IP address that the originating station
knows for the destination device, not the destination’s actual IP address. In
Figure 8-5 on page 8-11, for example, the local address is 10.1.1.1.