Linksys WRT51AB Router Manual PDF (Setup & Configuration Guide)

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Dual-Band Wireless A+B Broadband Router

The

Help

screen offers links to all of the Router’s technical support resources

and the application that upgrades the Router’s firmware. For additional infor-

mation about each screen of the web-based utility, click the appropriate link on

the lefthand side of the

Help

screen.

Firmware Version

The version number of the firmware currently installed is

displayed here. Firmware should only be upgraded if you are experiencing

problems with the Router. Visit

www.linksys.com

to find out if there is updated

firmware.

Linksys Website

Clicking this link will take you to Linksys’s website,

www.linksys.com

, provided you are connected to the Internet.

Online User Guide in PDF Format and Adobe Website

Clicking the

Online

User Guide in PDF format

link opens the Router’s User Guide. The User

Guide is in Adobe Acrobat Portable Document File (.pdf) format, so you need

the Adobe Acrobat Reader to view it. If you do not have the Acrobat Reader,

click the

Adobe website

link to download it.

Instant Wireless

Series

Help

Figure 6-17

The

Log

screen provides you with a log of all incoming or outgoing traffic for

your Internet connection.

Log

To monitor traffic between the network and the Internet, select the

Enable

radio button next to

Access Log

. The Log function can be disabled by clicking

the

Disable

radio button.

Incoming Access Log and Outgoing Access Log

Temporary logs can be

accessed by clicking either the

Incoming Access Log

Outgoing Access Log

button. The Incoming Access Log gives you a log of all the incoming Internet

traffic, displaying the source IP address and port number of the Router for each

activity. The Outgoing Access Log gives you a log of all outgoing Internet traf-

fic. For each activity, it displays the LAN IP address, the URL or IP address of

the Internet site accessed, as well as the service or port number used.

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.

Log

Figure 6-16

Page 27 / 69

Dual-Band Wireless A+B Broadband Router

The following instructions are for advanced users or users whose setup needs

require special configuration. When you click the

Advanced

tab, you will be

able to set up these features. There are six additional tabs available.

Advanced Wireless

- Allows you to customize data transmission and 802.1x

settings for your wireless network(s).

Filters

- Enables you to set up filters that block specific internal users from

Internet access.

Port Forwarding

- Lets you set up public services on your network, such as an

ftp server, mail server, or web server.

Routing

- Enables you to configure the routing mode of the Router.

DMZ Host

- Allows one local user to be exposed to the Internet for use of spe-

cial-purpose services such as online gaming or videoconferencing.

MAC Address Clone

- Allows you to copy or “clone” your Ethernet adapter’s

MAC address onto the Router.

If you need to access the basic configuration tabs, click the

Setup

tab.

Instant Wireless

Series

Advanced Tabs

Upgrade Firmware

New firmware versions are posted at

www.linksys.com

and can be downloaded for free. If the Router already works well, there’s no

need to download a newer firmware version, unless that version has a new fea-

ture that you want to use. (To learn about any new firmware with new features,

visit

www.linksys.com

.) Loading new firmware onto the Router does not always

enhance the speed or the quality of your connection.

To upgrade the Router’s firmware:

1. Download the firmware upgrade file from

www.linksys.com

, and extract

the file using a file archive utility such as WinZip.

2. Select the

Help

tab, if you haven’t already (see Figure 6-17).

3. Click

Upgrade Firmware

to display a new window, shown in Figure 6-18.

4. Click the

Browse...

button to find the firmware upgrade file you extracted.

Double-click the firmware upgrade file you extracted.

6. Click the

Upgrade

button, and follow the on-screen instructions.

Note:

By upgrading the Router’s firmware, you may lose the Router’s

configuration settings.

Figure 6-18

Important:

When you are upgrading the firmware, do NOT turn off

the Router, and do NOT press the Reset button.

Page 28 / 69

Dual-Band Wireless A+B Broadband Router

DTIM Interval

This value, between 1 and 16384, indicates the interval of the

Delivery Traffic Indication Message (DTIM). A DTIM field is a countdown

field informing clients of the next window for listening to broadcast and mul-

ticast messages. When the Router has buffered broadcast or multicast messages

for associated clients, it sends the next DTIM with a DTIM Interval value. Its

clients hear the beacons and awaken to receive the broadcast and multicast mes-

sages. The default value is

RTS Threshold

Should you encounter inconsistent data flow, only minor

reduction of the default value, 2346, is recommended. If a network packet is

smaller than the preset RTS threshold size, the RTS/CTS mechanism will not

be enabled. The Router sends Request to Send (RTS) frames to a particular

receiving station and negotiates the sending of a data frame. After receiving an

RTS, the wireless station responds with a Clear to Send (CTS) frame to

acknowledge the right to begin transmission. The RTS Threshold value should

remain at its default value of

2346

Fragmentation Threshold

This value specifies the maximum size for a pack-

et before data is fragmented into multiple packets. If you experience a high

packet error rate, you may slightly increase the Fragmentation Threshold.

Setting the Fragmentation Threshold too low may result in poor network per-

formance. Only minor reduction of the default value is recommended. In most

cases, it should remain at its default value of

2346

Transmission Rate

The rate of data transmission should be set depending on

the speed of your wireless network. You can select from a range of transmission

speeds (

, or

Mbps), or you can select

Best

to have the

Router automatically use the fastest possible data rate and enable the Auto-

Fallback feature. Auto-Fallback will negotiate the best possible connection

speed between the Router and a wireless client. The default value is

Best

Transmit Power

The greater the transmit power used, the larger the area a

wireless network covers. To minimize the likelihood of eavesdropping by unau-

thorized wireless users, do not use more transmit power than necessary to cover

the range needed for your wireless network. Try using the Router at different

levels of transmit power, and determine how much transmit power is needed to

reach the wireless client, such as a PC, or access point that is farthest from the

Router. Then select the appropriate level of transmit power (

Full

Half

Quarter

Eighth

, or

Min

) from the drop-down menu. The default value is

Full

Instant Wireless

Series

The

Advanced Wireless

screen allows you to customize data transmission set-

tings and access the

802.1x Configuration

screen. In most cases, the advanced

wireless settings on this screen should remain at their default values.

5GHz, 802.11a

Beacon Interval

The Beacon Interval value indicates the frequency interval of

the beacon. Enter a value between 20 and 1000. A beacon is a packet broadcast

by the Router to synchronize the wireless network. The default value is

100

Advanced Wireless

Figure 6-19

Page 29 / 69

Dual-Band Wireless A+B Broadband Router

802.1x Configuration

The

802.1x Configuration

screen allows you to alter the 802.1x settings for

your wireless network(s). Based on the Extensible Authentication Protocol

(EAP), the 802.1x standard specifies an authentication framework for a

wireless client to access a network, so network security is enhanced.

To access a network with 802.1x enabled, wireless clients, such as PCs,

must use 802.1x client software or Windows XP, which supports 802.1x.

Instant Wireless

Series

2.4GHz, 802.11b

Beacon Interval

The Beacon Interval value indicates the frequency interval of

the beacon. Enter a value between 20 and 1000. A beacon is a packet broadcast

by the Router to synchronize the wireless network. The default value is

100

RTS Threshold

Should you encounter inconsistent data flow, only minor

reduction of the default value, 2346, is recommended. If a network packet is

smaller than the preset RTS threshold size, the RTS/CTS mechanism will not

be enabled. The Router sends Request to Send (RTS) frames to a particular

receiving station and negotiates the sending of a data frame. After receiving an

RTS, the wireless station responds with a Clear to Send (CTS) frame to

acknowledge the right to begin transmission. The RTS Threshold value should

remain at its default value of

2346

Fragmentation Threshold

This value specifies the maximum size for a pack-

et before data is fragmented into multiple packets. If you experience a high

packet error rate, you may slightly increase the Fragmentation Threshold.

Setting the Fragmentation Threshold too low may result in poor network per-

formance. Only minor reduction of this value is recommended. In most cases,

it should remain at its default value of

2346

Preamble Type

The preamble defines the length of the CRC block for com-

munication between the Router and a roaming wireless network adapter. Select

the appropriate preamble type for your wireless network. (High network traffic

areas should use the shorter preamble type.) The default is

Long Preamble

Transmission Rate

The rate of data transmission should be set depending on

the speed of your wireless network. You can select from a range of transmission

speeds (

5.5

, or

Mbps), or you can select

Best

to have the Router auto-

matically use the fastest possible data rate and enable the Auto-Fallback fea-

ture. Auto-Fallback will negotiate the best possible connection speed between

the Router and a wireless client. The default setting is

Best

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.

802.1x Configuration

Click the

802.1x Configuration

button to customize

the Router’s 802.1x feature (see Figure 6-20).

Figure 6-20

Note:

If your wireless network does not have a RADIUS server, the

802.1x feature is not applicable to your network. (802.1x is an

advanced data security measure and not essential for router operation.)

Note:

For more details about 802.1x, refer to “Appendix C:

Configuring Wireless Security.”

Page 30 / 69

Dual-Band Wireless A+B Broadband Router

Instant Wireless

Series

RADIUS Server

The Router’s 802.1x feature works with a RADIUS server. It may also work

with other types of authentication servers, depending on the specifics of

each authentication server.

RADIUS Server IP Address

Enter the IP Address of the RADIUS server in

the field provided.

RADIUS Server Port

Enter the Port Number of the RADIUS server in the

field provided. The default is 1812.

Shared Secret

Enter the Shared Secret Key used by the Router and

RADIUS server during the authentication process.

5GHz, 802.11a

Disable/EAP-MD5/EAP-TLS/TTLS

Select

EAP-MD5

to enable use of

802.1x with MD5 authentication for the 5GHz, 802.11a network connection

between a wireless client and a RADIUS server (the Router acts as an

authenticator). Select

EAP-TLS/TTLS

to enable use of 802.1x with TLS or

TTLS authentication for the 5GHz, 802.11a network connection between a

wireless client and a RADIUS server (the Router acts as an authenticator).

To disable 802.1x authentication for your 5GHz, 802.11a network, keep the

default setting,

Disable

WEP Settings

If you are using 802.1x with MD5 authentication, then you

must click the

WEP Settings

button and set up a static key for WEP

encryption. This static key must be set on the Router’s

5GHz, 802.11a WEP

Settings

screen and on all 5GHz, 802.11a wireless clients.

Dynamic WEP Key Length

When 5GHz, 802.11a 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.

2.4GHz, 802.11b

Disable/EAP-MD5/EAP-TLS/TTLS

Select

EAP-MD5

to enable use of

802.1x with MD5 authentication for the 2.4GHz, 802.11b network connec-

tion between a wireless client and a RADIUS server (the Router acts as an

authenticator). Select

EAP-TLS/TTLS

to enable use of 802.1x with TLS or

TTLS authentication for the 2.4GHz, 802.11b network connection between

a wireless client and a RADIUS server (the Router acts as an authenticator).

To disable 802.1x authentication for your 2.4GHz, 802.11b network, keep

the default setting,

Disable

WEP Settings

If you are using 802.1x with MD5 authentication, then you

must click the

WEP Settings

button and set up a static key for WEP

encryption. This static key must be set on the Router’s

2.4GHz, 802.11b

WEP Settings

screen and on all 2.4GHz, 802.11b wireless clients.

Note:

Using MD5 authentication is less secure than using certificate-

based authentication (TLS or TTLS), because keys are not changed

automatically.

Important:

The Router’s 802.1x feature works with Windows XP.

It may also work with other Windows operating systems, depend-

ing on the specifics of your PC’s operating system and the 802.1x

client software being used.

Note:

Many authentication methods work within the 802.1x frame-

work. The Router supports MD5 and certificate-based (TLS or TTLS)

authentication methods. Using MD5 authentication is less secure than

using certificate-based authentication (TLS or TTLS), because keys

are not changed automatically.

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