Configuring Trigger Port; Table 15-6 Address Mapping Edit - ZyXEL Communications ZyWALL 5 User Manual

ZyWALL 5 Internet Security Appliance
LABEL
Type Choose the port mapping type from one of the following.
1. One-to-One: One-to-one mode maps one local IP address to one global IP address.
Note that port numbers do not change for One-to-one NAT mapping type.
2. Many-to-One: Many-to-One mode maps multiple local IP addresses to one global IP
address. This is equivalent to SUA (i.e., PAT, port address translation), ZyXEL's Single
User Account feature.
3. Many-to-Many Ov (Overload): Many-to-Many Overload mode maps multiple local IP
addresses to shared global IP addresses.
4. Many One-to-One: Many One-to-one mode maps each local IP address to unique
global IP addresses.
5. Server: This type allows you to specify inside servers of different services behind the
NAT to be accessible to the outside world.
Local Start IP This is the starting Inside Local IP Address (ILA). Local IP addresses are N/A for Server
port mapping.
Local End IP This is the end Inside Local IP Address (ILA). If your rule is for all local IP addresses,
then enter 0.0.0.0 as the Local Start IP address and 255.255.255.255 as the Local End
IP address.
This field is N/A for One-to-One and Server mapping types.
Global Start IP This is the starting Inside Global IP Address (IGA). Enter 0.0.0.0 here if you have a
dynamic IP address from your ISP.
Global End IP This is the ending Inside Global IP Address (IGA). This field is N/A for One-to-One,
Many-to-One and Server mapping types.
Apply Click Apply to save your changes back to the ZyWALL.
Cancel Click Cancel to exit this screen without saving.

15.6 Configuring Trigger Port

Some services use a dedicated range of ports on the client side and a dedicated range of ports on the
server side. With regular port forwarding you set a forwarding port in NAT to forward a service
(coming in from the server on the WAN) to the IP address of a computer on the client side (LAN). The
problem is that port forwarding only forwards a service to a single LAN IP address. In order to use the
same service on a different LAN computer, you have to manually replace the LAN computer's IP
address in the forwarding port with another LAN computer's IP address,
Trigger port forwarding solves this problem by allowing computers on the LAN to dynamically take
turns using the service. The ZyWALL records the IP address of a LAN computer that sends traffic to
the WAN to request a service with a specific port number and protocol (a "trigger" port). When the
ZyWALL's WAN port receives a response with a specific port number and protocol ("incoming" port),
the ZyWALL forwards the traffic to the LAN IP address of the computer that sent the request. After
that computer's connection for that service closes, another computer on the LAN can use the service in
the same manner. This way you do not need to configure a new IP address each time you want a
different LAN computer to use the application.
For example:
15-10

Table 15-6 Address Mapping Edit

DESCRIPTION
NAT