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DSL-504T DSL Router User
s Guide
33
Port Forwarding
Use the Port Forwarding menu to create Virtual Server functions through the Router. A Virtual
Server can allow remote users to access services on your LAN such as FTP for file transfers or
SMTP and POP3 for e-mail. The DSL-504T will accept remote requests for these services at your
Global IP Address, using the specified TCP or UDP protocol and port number, and then redirect
these requests to the server on your LAN with the Private IP address you specify. Remember that
the Private IP Address must be within the range specified for your LAN.
The Virtual Server feature employs UDP/TCP port redirection to direct traffic through the WAN port
to specified servers on your private network. Port redirection can also be used to direct potentially
hazardous packets to a proxy server outside your firewall. For example, you can configure the
Router to direct HTTP packets to a designated HTTP server in the DMZ. You can define a set of
instructions for a specific incoming port or for a range of incoming ports. Each instruction set or
rule is indexed and can be modified or deleted later as needed.
Virtual server configuration sets can be used together with complimentary features such as Firewall
Rules, DMZ devices and IP Filters to improve efficiency and security. Consider how these other
functions will effect the virtual server sets you have configured and enabled.
The table below describes the configuration settings presented in the Virtual Server menu.
Virtual Server Menu and List
To modify virtual server settings for any previously created virtual server set listed, click on the
note pad icon in the right hand column of the
Virtual Servers List
for the set you want to
configure. The set will appear highlighted in the list and the parameters that have been configured
appear in the settings fields above the list. Adjust the settings as desired and click the
Apply
button to put them into effect.
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DSL-504T DSL Router User
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34
To configure a virtual server set, define the following settings in the Virtual Server configuration
menu located in the top half of the browser window.
Parameter
Description
Rule Name
Provide a name for the rule. This name will not appear in the list
below, however it may be useful if you later need to edit the
settings for the rule. Rule names are optional.
Private IP
This is the IP address of the server on your LAN that will provide
the service to remote users. The Private IP address is used to
direct the service to a specific computer on your private network
such as an FTP, Email or public web server. Type in the IP
address of the server used for the service being configured here.
Protocol
You can select the transport protocol (TCP or UDP) that the
application on the virtual server will use for its connections.
Select one of the following options from the pull-down menu to
define a
TCP
,
UDP
or
Both
. The choice of this protocol is
dependent on the application that is providing the service.
If you
do not know which protocol to choose, check your application
s
documentation.
Port Start /Port End
Configure a range of ports for forwarding. Type the lowest
numbered port in the range in the Port Start space. Type the
highest numbered port in the Port End space. For a single port,
just enter the same number in both spaces.
Virtual server port redirection must be used with a specified
server or computer on the LAN (identified by the Private IP
address).
Port Map
This is the local port being forwarded to from the Port Start/Port
End port(s). Keep in mind that if you use a non-standard port
number for an application with a reserved UDP/TCP port, some
additional configuration may be required for the servers or
workstations using the application on the LAN side.
Click the
Apply
button to put the new virtual server configuration set or modification into effect.
Any server sets configured in the menu will appear in the Virtual Server List with the new settings.
The Router must save the new settings and reboot before the new virtual server configurations are
applied.
To remove any configuration set from the Virtual Server List, click on the trashcan icon for set you
want to delete.
Note
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DSL-504T DSL Router User
s Guide
35
DMZ
Since some applications are not compatible with NAT, the Router supports use of a DMZ IP address
for a single host on the LAN. This IP address is not protected by NAT and will therefore be visible to
agents on the Internet with the right type of software. Keep in mind that any client PC in the DMZ
will be exposed to various types of security risks. If you use the DMZ, take measures (such as
client-based virus protection) to protect the remaining client PCs on your LAN from possible
contamination through the DMZ.
DMZ IP address configuration
To designate a DMZ IP address, select the
Enabled
radio button, type in the
IP Address
of the
server or device on your LAN, and click the
Apply
button. To remove DMZ status from the
designated IP address, select the Disabled radio button and click Apply. It will be necessary to save
the settings and reboot the Router before the DMZ is activated.
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DSL-504T DSL Router User
s Guide
36
Filters
Filter rules in the Router are put in place to allow or block specified traffic. The Filter Rules however
can be used in a single direction to examine and then Allow or Deny traffic for Inbound (WAN to
LAN) or Outbound (LAN to WAN) routed data. The rules based on IP address and TCP/UDP port.
Configure the filter rules as desired and click the
Apply
button to create the rule. The newly
created rule appears listed in the Outbound Filter List at the bottom of the menu. The table below
describes the various parameters that are configured for the filter rules.
Filters Configuration Menu
To modify any previously created filter rule, click on the note pad icon in the right hand column of
the Filter List for the set you want to configure. Adjust the settings as desired and click the
Apply
button to put the new settings into effect.
First determine the direction of the traffic you want the rule to filter. To filter WAN to LAN traffic,
select the
Inbound Filter
option. Any new Inbound Filter rules created will appear in the list.
Likewise, should you to filter LAN to WAN traffic, create an
Outbound Filter
rule.
Note
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DSL-504T DSL Router User
s Guide
37
The parameters described below are used to set up filter rules.
Parameter
Description
Source IP
For an Outbound Filter, this is the IP address or IP addresses on your LAN
for which you are creating the filter rule. For an Inbound Filter, this is the
IP address or IP addresses for which you are creating the filter rule. You
can opt to indicate a
Mask Range
, a
Single IP
, an
IP Range
or
Any IP
from
the pull-down menu. Choosing Any IP will apply the rule to all WAN or all
LAN IP addresses depending on which type of rule (Inbound or Outbound)
is being configured.
Destination IP
Where the Destination IP address resides also depends on if you are
configuring an Inbound or Outbound filter rule. You can opt to indicate a
Mask Range
, a
Single IP
, an
IP Range
or
Any IP
from the pull-down menu.
Source Port
The Source Port is the TCP/UDP port on either the LAN or WAN depending
on if you are configuring an Outbound or Inbound Filter rule. Select one of
the following options from the pull-down menu to define a
Any Port, Single
Port
,
Port Range
or
Safe Range
(ports above 1024).
Destination Port
The Destination Port is the TCP/UDP port on either the LAN or WAN
depending on if you are configuring an Outbound or Inbound Filter rule.
Select one of the following options from the pull-down menu to define a
Any Port, Single Port
,
Port Range
or
Safe Range
(ports above 1024).
Protocol
Select the transport protocol (
TCP
,
UDP
or
All
) that will be used for the
filter rule.
Action
Select to
Allow
or
Deny
transport of the data packets according to the
criteria defined in the rule. Packets that are allowed are routed to their
destination; packets that are denied are blocked.
Click the
Apply
button to put the new rule into effect. Any filter rule configured in the menu will
appear in the Filters List with the new settings. The Router must save the new settings and reboot
before the new rules are applied.

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