SMC Networks SMCD3G, User Manual

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Configuring Your Gateway
Configuring Special Applications
Using the Special Application menu, you can configure your 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, your 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.
The maximum allowed triggers is 50. To enable/disable the special application function,
users can check/uncheck the Enable Triggering checkbox and press the APPLY icon to
make it effective without reboot.
To display the Special Applications menu, click Firewall in the menu bar and then click the
Special Application submenu. Figure 26 shows an example of the menu.
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SMCD3G Cable Modem Gateway User Manual