ZyXEL Communications 10 - Manual (Page 165)

ZyWALL 10~100 Series Internet Security Gateway
NAT 12-23
12.5.4 Example 4: NAT Unfriendly Application Programs
Some applications do not support NAT Mapping using TCP or UDP port address translation. In this case it
is better to use Many-One-to-One mapping as port numbers do not change for Many-One-to-One (and
One-to-One) NAT mapping types. The following figure illustrates this.
Figure 12-21 NAT Example 4
Other applications such as some gaming programs are NAT unfriendly because
they embed addressing information in the data stream. These applications won’t
work through NAT even when using One-to-One and Many-One-to-One mapping
types.
Follow the steps outlined in example 3 above to configure these two menus as follows.