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ProSafe Wireless-N 8-Port Gigabit VPN Firewall FVS318N
Configure Port Triggering
Port triggering allows some applications running on a LAN network to be available to external
applications that would otherwise be partially blocked by the firewall. Using the port triggering
feature requires that you know the port numbers used by the application.
Note: Port triggering is supported for IPv4 devices only.
Once configured, port triggering operates as follows:
1. A computer make
s an outgoing connection using a port number that is defined in the
Port Triggering Rules table.
2. Th
e wireless VPN firewall records this connection, opens the additional incoming port or
ports that are associated with the rule in the port triggering table, and associates them with
the computer.
3. The
remote system receives the computer’s request and responds using the incoming port
or ports that are associated with the rule in the port triggering table on the wireless VPN
firewall.
4. Th
e wireless VPN firewall matches the response to the previous request and forwards the
response to the computer.
Without port triggering, the response from the external
application would be treated as a new
connection request rather than a response to a request from the LAN network. As such, it
would be handled in accordance with the inbound port forwarding rules, and most likely
would be blocked.
Note these restrictions on port triggering:
• On
ly one computer can use a port triggering application at any time.
• Af
ter a computer has finished using a port triggering application, there is a short time-out
period before the application can be used by another computer. This time-out period is
required so the wireless VPN firewall can determine that the application has terminated.
Note: For additional ways of allowing inbound traffic, see Inbound Rules
(Port Forwarding) on page 133.
To add a port triggering rule:
1. Select Secu
rity > Port Triggering. The Port Triggering screen displays. (The following
figure shows a rule in the Port Triggering Rules table as an example.)