Netgear FVS336G FVS336G Reference Manual - Page 80

ProSafe Dual WAN Gigabit Firewall with SSL & IPsec VPN FVS336G Reference Manual Configuring Port Triggering Port triggering allows some applications to function correctly that would otherwise be partially blocked by the firewall when the router is in NAT mode. Some applications require that when external devices connect to them, they receive data on a specific port or range of ports. The router must send all incoming data for that application only on the required port or range of ports. Using this feature requires that you know the port numbers used by the application. Port triggering allows computers on the private network (LAN) to request that one or more ports be forwarded to them. Unlike basic port forwarding which forwards ports to only one preconfigured IP address, port triggering waits for an outbound request from the private network on one of the defined outgoing ports. It then automatically sets up forwarding to the IP address that sent the request. When the application ceases to transmit data over the port, the router waits for a timeout interval and then closes the port or range of ports, making them available to other computers on the private network. Once configured, port triggering operates as follows: 1. A PC makes an outgoing connection using a port number defined in the Port Triggering table. 2. The VPN firewall records this connection, opens the additional incoming port or ports associated with this entry in the Port Triggering table, and associates them with the PC. 3. The remote system receives the PC's request and responds using the different port numbers that you have now opened. 4. The VPN firewall matches the response to the previous request, and forwards the response to the PC. Without Port Triggering, this response would be treated as a new connection request rather than a response. As such, it would be handled in accordance with the inbound service rules. Note these restrictions with Port Triggering: • Only one PC can use a port triggering application at any time. • After a PC has finished using a port triggering application, there is a time-out period before the application can be used by another PC. This is required because the VPN firewall cannot be sure when the application has terminated. Note: For additional ways of allowing inbound traffic, see "Inbound Rules (Port Forwarding)" on page 4-5. 4-24 Firewall Protection and Content Filtering v1.0, March 2009