Advanced Settings

61

N450 WiFi Cable Modem Router Model N450/CG3000Dv2

A login screen displays.

2.

Enter the modem router user name and password.

The default user name is

admin

. The default password is

password

. The user name and

password are case-sensitive.

The modem router main menu displays.

3.

In the main menu, under Advanced, select

Port Blocking

.

The Port Blocking screen displays.

4.

Click the

Reset

button.

The

Add Custom Service

table is cleared, or the radio button you selected from the

Active Filters

table is unselected.

Port Forwarding

A firewall has default rules for inbound traffic (WAN to LAN) and for outbound traffic. Port

forwarding affects the inbound rules. These rules restrict access from outsiders. By default,

the modem router blocks access from outside except for responses to requests from the LAN

side. You can use port forwarding to add rules to specify exceptions to the default rule.

Because the modem router uses Network Address Translation (NAT), your network presents

only one IP address to the Internet, and outside users cannot directly address any of your

local computers. However, by defining an inbound rule you can make a local server (for

example, a web server or game server) or computer visible and available to the Internet. The

rule tells the modem router to direct inbound traffic for a particular service to one local server

or computer based on the destination port number. Directing traffic is also known as port

forwarding.

Some residential broadband ISPs do not allow you to run server processes (such as a web or

FTP server) from your location. Your ISP might check for servers and suspend your account

if it finds active services at your location. See the ISP’s Acceptable Use policy.

Pay attention to the following considerations before configuring port forwarding:

•

If DHCP assigns the IP address of the local server computer, the address might change

when the computer is rebooted. To keep the address from changing, you can assign a

static IP address to your server outside the range that DHCP assigns, but in the same

Advanced Settings

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N450 WiFi Cable Modem Router Model N450/CG3000Dv2

subnet as your LAN. By default, the IP addresses from 192.168.0.2 through 192.168.0.9

are reserved for this purpose.

•

Local computers must access the local server using the computers’ local LAN address

(192.168.0.XXX, by default). Attempts by local computers to access the server using the

external WAN IP address fail.

•

Port forwarding opens holes in your firewall. Enable only ports that are necessary.



To configure port forwarding and services for specific inbound traffic:

1.

Type

in the address field of your web browser.

A login screen displays.

2.

Enter the modem router user name and password.

The default user name is

admin

. The default password is

password

. The user name and

password are case-sensitive.

The modem router main menu displays.

3.

In the main menu, under Advanced, select

Port Forwarding

.

4.

From the

Service

list, select the service for which you want to configure port forwarding.

The following screen displays:

5.

To add a custom rule that is not in the list of services, specify these settings in the Add

Custom Rules table:

Advanced Settings

63

N450 WiFi Cable Modem Router Model N450/CG3000Dv2

•

Name

. A name for the service.

•

Start Port

. The start port for the service.

•

End Port

. The end port for the service.

•

Protocol

. The protocol for the ports:

-

TCP

. TCP only.

-

UDP

. UDP only.

-

Both

. Both TCP and UDP.

•

Local IP Address

. Complete the local IP address for the computer that is using the

service.

6.

Perform one of these actions:

•

Click the

Add

button. The Active Forwarding Rules table displays the list of forwarded

ports.

•

To delete a service, select the radio button in the Active Forwarding Rules table for

the service that you want to delete, and click the

Delete

button.

•

To reset the selection in the

Service

list and to clear all the fields in the Add Custom

Rules, click the

Reset

button.

Port Triggering

Port triggering is an advanced feature that you can use to allow gaming and other Internet

applications that the firewall would otherwise block. You must know the port numbers the

application uses. Port triggering operates as follows:

1.

A computer makes an outgoing connection using a port number defined in the Port

Triggering table.

2.

The modem router records this connection, opens the incoming port or ports associated with

this entry in the Port Triggering List, and associates them with the computer.

3.

The remote system receives the computer’s request, and responds using a different port

number.

4.

The modem router matches the response to the previous request, and forwards the

response to the computer. (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 port forwarding rules.)

Note:

Only one computer at a time can use port triggering. After a computer

finishes using a port triggering application, a short time-out period

passes before another computer can use the application.



To configure port triggering:

1.

Type

in the address field of your web browser.

Advanced Settings

64

N450 WiFi Cable Modem Router Model N450/CG3000Dv2

A login screen displays.

2.

Enter the modem router user name and password.

The default user name is

admin

. The default password is

password

. The user name and

password are case-sensitive.

The modem router main menu displays.

3.

In the main menu, under Advanced, select

Port Triggering

.

The following screen displays:

4.

For each port trigger, enter the settings in the Port Triggering List:

•

Trigger Range

. To specify the range of outgoing ports that are monitored to trigger

the incoming port forwarding rule, enter the start port and end port.

•

Target Range

. To specify the range of incoming ports that are opened when

triggered, enter the start port and end port.

•

Protocol

. Select the protocol for the ports:

-

TCP

. TCP only.

-

UDP

. UDP only.

Advanced Settings

65

N450 WiFi Cable Modem Router Model N450/CG3000Dv2

-

Both

. Both TCP and UDP.

5.

Select the

Enable

check box for the port trigger.

6.

Click the

Apply

button.

Your changes are saved and the port trigger is activated.



To remove a configured port trigger from the table:

1.

Type

in the address field of your web browser.

A login screen displays.

2.

Enter the modem router user name and password.

The default user name is

admin

. The default password is

password

. The user name and

password are case-sensitive.

The modem router main menu displays.

3.

In the main menu, under Advanced, select

Port Triggering

.

The port triggering screen displays.

4.

Select the radio button next to the port trigger.

5.

Click the

delete

button.

The port trigger is removed.



To return all trigger and target ranges to zero:

1.

Type

in the address field of your web browser.

A login screen displays.

2.

Enter the modem router user name and password.