Chapter 8 Network Address Translation (NAT)

 

Table 38 Port Forwarding Edit (continued)

 

LABEL

DESCRIPTION

 

External Start

Enter the original destination port for the packets.

 

Port

To forward only one port, enter the port number again in the External

 

 

 

 

End Port field.

 

 

To forward a series of ports, enter the start port number here and the

 

 

end port number in the External End Port field.

 

 

 

 

External End

Enter the last port of the original destination port range.

 

Port

To forward only one port, enter the port number in the External Start

 

 

 

 

Port field above and then enter it again in this field.

 

 

To forward a series of ports, enter the last port number in a series that

 

 

begins with the port number in the External Start Port field above.

 

 

 

 

Internal Start

Enter the port number here to which you want the P-870HN-51D to

 

Port

translate the incoming port. For a range of ports, enter the first number

 

 

of the range to which you want the incoming ports translated.

 

 

 

 

Internal End

Enter the last port of the translated port range.

 

Port

 

 

 

 

 

Server IP

Enter the inside IP address of the virtual server here.

 

Address

 

 

 

 

 

Protocol

Select the transport layer protocol supported by this virtual server.

 

 

Choices are TCP, UDP, or TCP/UDP.

 

 

 

 

Back

Click Back to return to the previous screen.

 

 

 

 

Apply

Click Apply to save your changes back to the P-870HN-51D.

 

 

 

 

Cancel

Click Cancel to begin configuring this screen afresh.

 

 

 

8.4 The Trigger Port Screen

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 P-870HN-51D 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 P-870HN-51D's WAN port receives a response with a specific port number and protocol ("open" port), the P-870HN-51D forwards the traffic to the LAN IP address of the computer that sent the request. After that computer’s connection for that service closes,

 

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P-870HN-51D User’s Guide