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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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