Port Filtering

The Port Filtering page allows you to configure port filters in order to block Internet traffic to specific

ports on all devices on your LAN.

Similarly, you can prevent PCs from sending outgoing TCP/UDP traffic to the Internet from specific

IP port numbers. This can be configured using the Port Filtering page.

To access the

Port Filtering

page:

1

Click

Advanced

in the menu bar.

2

Then click the

Port Filtering

submenu.

Figure 17 shows an example of the menu and Table 12 describes the items you can select.

Figure 17. Example of Port Filtering Page

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For example

, if you would like to block all PCs on the private LAN from accessing HTTP sites (or

“web surfing”):

1

Set the Start Port to

80

, the End Port to

80

.

2

Set the protocol to

TCP

.

3

Check the

Enable

box to the right of the entry to store settings.

4

Click

Apply

button to activate the filter rules.

Table 12. Port Filtering Menu Option

Option

Description

Start/End Port

Enters the start and end port of the port filter range

Protocol

Filter either both TCP and UDP traffic or just UDP or just TCP.

Forwarding

The Forwarding page allows you to run a publicly accessible server from your LAN by specifying the

mapping of TCP/UDP ports to a local PC. It allows incoming requests to specific port numbers to

reach a web server, FTP server, mail server, etc.

To access the

Forwarding

page,

1

Click

Advanced

in the menu bar.

2

Then click the

Forwarding

submenu.

Figure 18 shows an example of the menu and Table 13 describes the items you can select.

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Figure 18. Example of Forwarding Page

To activate the port forwarding:

1

Enter the port range of the Internet traffic that you want to forward, and the IP address of the

server to which you want to forward that traffic.

2

Select the protocol(s) to be forwarded.

3

Check the

Enable

box to the right of the entry to store settings.

4

Click the

Apply

button to activate the forwarding rules.

Table 13. Forwarding Menu Option

Option

Description

Local IP Address

Enter the IP address to which forwarded traffic should be sent.

Start/End Port

Enter the range of port numbers (start and end port) to forward. If only a

single port is desired, enter the same port number in the

Start

and

End

locations.

Protocol

Select the protocol(s) to be forwarded.

Note:

You may need to assign static IP addresses to devices on your LAN to insure that the port

forwarding you have set up will always apply to them.

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Port Triggers

The Port Triggers page allows you to configure dynamic triggers to specific devices on the LAN. This

allows for special applications that require specific port numbers with bi-directional traffic to

function properly. Applications such as video conferencing, voice, gaming, and some messaging

program features may require these special settings.

Port Triggers are similar to Port Forwarding except that they are not static ports held open all the

time. With the port triggering function, the cable modem/router detects outgoing data on a specific

IP port number and opens corresponding target ports for incoming data. If no outgoing traffic is

detected on the Trigger Range ports for 10 minutes, the Target Range ports will close.

To access the

Port Triggers

page:

1

Click

Advanced

in the menu bar.

2

Then click the

Port Triggers

submenu.

Figure 19 shows an example of the menu and Table 14 describes the items you can select.

Figure 19. Example of port Triggers Page

To activate a port trigger

1

Enter the trigger and target ports range for the Internet traffic to forward to.

2

Select the forwarding protocol(s).

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3

Check the

Enable

box to the right of the entry to store settings.

4

Click the

Apply

button to activate the forwarding rules.

Table 14. Port Triggers Menu Option

Option

Description

Trigger Range

(Start / End

Port)

Enter the trigger range (starting and ending ports) of the application for which

you want to enable port triggering. The application will send data from these

ports.

Target Range

(Start / End

Port)

Enter the target range (starting and ending ports) to open for the same

application. The application will receive data on these ports.

Protocol

Select the protocol for this rule.

DMZ Host

The DMZ (De-militarized Zone) Host page allows you to configure a network device (e.g. a PC) to be

exposed or visible directly to the Internet. This may be used if an application doesn’t work with port

triggers. If you have an application that won’t run properly behind the NAT firewall, you can

configure it for unrestricted two-way Internet access by defining it as a virtual DMZ host. Adding a

client to the DMZ may expose your local network to various security risks because the client is not

protected, so use this option as a last resort.

To access the

DMZ Host

page:

1

Click

Advanced

in the menu bar.

2

Then click the

DMZ Host

submenu.

Figure 20 shows an example of the menu.

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