User's Manual

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SMCD3GN2 Wireless Cable Modem Gateway Administrator Manual
Configuring Special Applications
Using the Special Application menu, you can configure the Gateway to detect port triggers
for detect multiple-session applications and allow them to pass the firewall. For special
applications, besides the initial communication session, there are multiple related sessions
created during the protocol communications. Normally, a normal treats the triggered
sessions as independent sessions and blocks them. However, the Gateway can co-relate
the triggered sessions with the initial session and group them together in the NAT session
table. As a result, you need only specify which protocol type and port number you want to
track, as well as some other related parameters. In this way, the Gateway can pass the
special applications according to the supplied information.
Assume, for example, that to use H.323 in a Net Meeting application, a local client starts a
session A to a remote host. The remote host uses session A to communicate with the local
host, but it also could initiate another session B back to the local host. Since there is only
session A recorded in the NAT session table when the local host starts the communication,
session B is treated as an illegal access from the outside and is blocked. Using the Special
Application menu, you can configure the Gateway to co-relate sessions A and B and
automatically open the port for the incoming session B.
To display the Special Applications menu, click Firewall in the menu bar and then click the
Special Application submenu. Figure 62 shows an example of the menu.
The maximum allowed triggers is 50. To enable the special application function, check the
Enable Triggering checkbox and click Apply. To disable it, uncheck the Enable Triggering
checkbox and click Apply.
Note: The Special Application submenu is not available in the menu bar if
Enable Firewall Module is disabled in the Security Settings (Firewall) menu (see
page 105).