Linksys WRT51AB Router Manual PDF (Setup & Configuration Guide)

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Dual-Band Wireless A+B Broadband Router

The

Filters

screen allows you to block specific internal users from accessing

the Internet. You can set up filters by using MAC addresses, IP addresses, or

network port numbers (or a range of ports).

Filtered Private Port Range

To filter users by network port number, select

Both

TCP

, or

UDP

, depending on which protocols you want to filter. Then

enter the port numbers you want to filter into the port number fields. Users

connected to the Router will no longer be able to access any port number list-

ed there. To disable a filter, select

Disable

Instant Wireless

Series

Dynamic WEP Key Length

When 2.4GHz, 802.11b wireless clients are

using certificate-based authentication (EAP-TLS or EAP-TTLS), dynamic

WEP keys are automatically generated. Select the length of the Dynamic

Key (

128

-bit) from the drop-down menu.

Key Renewal Timeout

If you are using dynamic WEP keys (available only

for EAP-TLS or EAP-TTLS authentication), enter the number of seconds

that will elapse before the Dynamic Key automatically changes. The default

300

seconds.

Port Inactivity Timeout

After the wireless client has been authenticated, the

Router monitors activity on the port being used. In the

Port Inactivity

Timeout

field, enter the number of seconds the port can be inactive before

the client automatically forced to reauthenticate. The default is

600

seconds.

Port Connectivity Timeout

After the Router requests the identity of a wire-

less client, the client must respond with an identity message within a cer-

tain length of time. In the

Port Connectivity Timeout

field, enter the number

of seconds the client has to respond within before the connection is termi-

nated. The default is

300

seconds.

To apply any of the settings you change on this page, click the

Apply

button.

cancel any changes you’ve entered on this page, click the

Cancel

button. To get

more information about the features, click the

Help

button.

Filters

Figure 6-21

Page 32 / 69

Dual-Band Wireless A+B Broadband Router

Instant Wireless

Series

If you want to enter more than ten MAC addresses, select

MAC Addresses 1-

11-20

21-30

31-40

, or

41-50

from the drop-down menu to enter addition-

al MAC addresses, up to a maximum of 50. Then click the

Apply

button to save

the MAC addresses.

To disable Private MAC Filtering, select

Disable

Block WAN Request

By enabling the Block WAN Request feature, you can

prevent your network from being “pinged,” or detected, by other Internet users.

The Block WAN Request feature also reinforces your network security by hid-

ing network ports. Both functions of the Block WAN Request feature make it

more difficult for outside users to work their way into your network. The

default is

Enable

IPSec Pass-Through

The Router supports IPSec Pass-Through. Internet

Protocol Security (IPSec) is a suite of protocols used to implement secure

exchange of packets at the IP layer, and it is one of the methods used to enable

Virtual Private Networking (VPN) tunnels. IPSec is more secure than PPTP.

The default is

Enable

PPTP Pass-Through

The Router supports PPTP Pass-Through. Point-to-Point

Tunneling Protocol (PPTP) is one of the methods used to enable VPN tunnels.

PPTP is less secure than IPSec. The default is

Enable

Remote Management

This feature allows you to manage the Router from a

remote location, via the Internet. To enable this feature, select

Enable

, and use

the specified port (default is

8080

) on your PC to remotely manage the Router.

The default is

Disable

MTU

MTU is the Maximum Transmission Unit. It specifies the largest pack-

et size permitted for network transmission. To use this feature, select

Enable

and enter the value desired. You should leave this value in the 572 to 1492

range. The default is

Disable

To apply any of the settings you change on this page, click the

Apply

button.

cancel any changes you’ve entered on this page, click the

Cancel

button. To get

more information about the features, click the

Help

button.

Private IP Filter

To set up a filter

using IP addresses, select

Enable

Then select

Only Allow Internet

Access for the IP Addresses on the

List

Only Deny Internet Access for

the IP Addresses on the List

Click the

Edit IP Filter List

button.

Enter the appropriate IP addresses into

the IP address fields (see Figure 6-22).

Each IP address should be entered in

this format: xxx.xxx.xxx.xxx (the x’s

represent the actual digits of the IP

address).

If you want to enter more than ten IP

addresses, select

IP Addresses 1-10

11-20

21-30

31-40

, or

41-50

from the

drop-down menu to enter additional IP

addresses, up to a maximum of 50.

Then click the

Apply

button to save the

IP addresses.

To disable Private IP Filtering, select

Disable

Private MAC Filter

To set up a filter

using MAC addresses, select

Enable

Then select

Only Allow Internet

Access for the MAC Addresses on

the List

Only Deny Internet Access

for the IP Addresses on the List

Click the

Edit MAC Filter List

but-

ton. Enter the appropriate MAC

addresses into the MAC address fields

(see Figure 6-23). Each MAC address

should be entered in this format:

xx:xx:xx:xx:xx:xx (the x’s represent

the actual characters of the MAC

address).

Figure 6-22

Figure 6-23

Page 33 / 69

Dual-Band Wireless A+B Broadband Router

TCP Protocol

Click this checkbox if you want to forward the data transmis-

sions that use the TCP protocol.

UDP Protocol

Click this checkbox if you want to forward the data transmis-

sions that use the UDP protocol.

IP Address

For each application, enter the

IP Address

of the PC running the

specific application.

Enable

Click the

Enable

checkbox to enable port forwarding for the relevant

application.

The following table shows the typical port forwarding settings for common

Internet applications.

To apply any of the settings you change on this page, click the

Apply

button.

cancel any changes you’ve entered on this page, click the

Cancel

button. To get

more information about the features, click the

Help

button.

Instant Wireless

Series

FTP

Applications

External Port

TCP Protocol

UDP Protocol

Telnet

SMTP

DNS

TFTP

Finger

HTTP

POP3

110

NNTP

119

SNMP

161

The

Port Forwarding

screen sets up public services on your network, such as

web servers, ftp servers, e-mail servers, or other specialized Internet applica-

tions. (Specialized Internet applications are any applications that use Internet

access to perform functions such as videoconferencing or online gaming. Some

Internet applications may not require any forwarding.)

Customized Applications

In the field provided, enter the name you wish to

give each application.

External Port

For each application, enter the number of the External Ports

(the port numbers seen by users on the Internet) in the appropriate fields. (To

find out the port range, check your application’s documentation.) If there is

only one External Port, enter its number in both

External Port

fields.

Port Forwarding

Figure 6-24

Note:

Any PC whose port is being forwarded should have its DHCP

client function disabled and a new static IP address assigned to it

because its IP address may change when using the DHCP function.

Page 34 / 69

Dual-Band Wireless A+B Broadband Router

Instant Wireless

Series

2. If you selected the

Gateway

mode, click the

Apply

button. If you selected

the

Router

mode, proceed to step 3.

3. For

Dynamic Routing

, the default is

Enable

. The Dynamic Routing feature

enables the Router to automatically adjust to physical changes in the net-

work’s layout and exchange routing tables with the other router(s). The

Router determines the network packets’ route based on the fewest number

of hops between the source and the destination. Select

Disable

to disable

the Dynamic Routing feature for data transmissions.

To set up a static route between the Router and another network, select a

number from the

Static Routing

drop-down list. (A static route is a pre-

determined pathway that network information must travel to reach a spe-

cific host or network.)

5. Enter the following data:

•

Destination LAN IP -

The Destination LAN IP is the address of the

remote network or host to which you want to assign a static route.

•

Subnet Mask -

The Subnet Mask determines which portion of a

Destination LAN IP address is the network portion, and which portion

is the host portion.

•

Default Gateway -

This is the IP address of the gateway device that

allows for contact between the Router and the remote network or host.

To cancel your changes, click the

Cancel

button. To save your changes,

click the

Apply

button. To get more information about the features, click

the

Help

button.

To delete a static route entry:

From the

Static Routing

drop-down list, select the entry number of the stat-

ic route.

Click the

Delete This Entry

button.

To cancel a deletion, click the

Cancel

button. To save a deletion, click the

Apply

button. To get more information about the features, click the

Help

button.

On the

Routing

screen, you can set the routing mode of the Router.

Gateway

mode is recommended for most users.

To set up routing:

Choose the correct working mode. Select

Gateway

if the Router is hosting

your network’s connection to the Internet (recommended for most users).

Select

Router

if the Router exists on a network with other routers.

Routing

Figure 6-25

Note:

The

Routing

screen and available features will vary depending

on which mode you select.

Note:

If you have more than one router on your network, you should

select

Router

for the working mode.

Page 35 / 69

Dual-Band Wireless A+B Broadband Router

Instant Wireless

Series

The

DMZ Host

screen lets you enable the DMZ hosting feature, which allows

one local user to be exposed to the Internet for use of a special-purpose serv-

ice such as Internet gaming or videoconferencing. Whereas port forwarding

can only forward a maximum of ten port ranges, DMZ hosting forwards all the

ports to one PC simultaneously. It is recommended to use Port Forwarding

whenever possible because it is more secure.

To expose one PC to the Internet:

Click the

Enable

radio button.

Enter the computer’s IP address in the

DMZ Host IP Address

field.

To cancel your changes, click the

Cancel

button. To save your new settings,

click the

Apply

button. To get more information about the features, click

the

Help

button.

Note:

Any PC whose ports are being forwarded should have its DHCP

client function disabled and a new static IP address assigned to it

because its IP address may change when using the DHCP client function.

DMZ Host

Figure 6-27

Show Routing Table

Click the

Show Routing Table

button to view all of the

valid dynamic and static route entries in use (see Figure 6-26). The Destination

LAN IP address, Subnet Mask, Gateway, and Interface information are dis-

played for each entry. Click the

Refresh

button to display the most up-to-date

data.

Figure 6-26

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