Linksys WRT51AB Router Manual PDF (Setup & Configuration Guide)

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Dual-Band Wireless A+B Broadband Router

13. The firmware upgrade failed, and/or the Diag LED is flashing.

The upgrade could have failed for a number of reasons.

Follow these steps to

upgrade the firmware and/or make the Diag LED stop flashing:

If the firmware upgrade failed, use the

TFTP

program (it was downloaded

along with the firmware). Open the pdf that was downloaded along with the

firmware and TFTP program, and follow the pdf’s instructions.

Set a

static IP address

on the PC; refer to “Problem #1, I need to set a stat-

ic IP address.” Use the following IP address settings for the computer you

are using:

IP Address: 192.168.1.50

Subnet Mask: 255.255.255.0

Gateway: 192.168.1.1

Perform the upgrade using the TFTP program or the Router’s web-based

utility through its Help tab.

14. My DSL service’s PPPoE is always disconnecting.

PPPoE is not actually a dedicated or always-on connection.

The DSL ISP can

disconnect the service after a period of inactivity, just like a normal phone dial-

up connection to the Internet.

There is a setup option to “keep alive” the con-

nection.

This may not always work, so you may need to re-establish connec-

tion periodically.

A. To connect to the Router, go to the web browser, and enter

http://192.168.1.1

or the

IP address

of the Router.

Enter the

password

, if asked. (The default password is

admin

C. On the

Setup

screen, select the option

Keep Alive

, and set the

Redial

Period

option at

(seconds).

Click the

Apply

button.

Click the

Status

tab, and click the

Connect

button.

You may see the login status display as

Connecting

. Press the

key to

refresh the screen, until you see the login status display as

Connected

Click the

Apply

button to continue.

If the connection is lost again, follow steps E to G to re-establish connection.

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10. I am a PPPoE user, and I need to remove the proxy settings or the dial-up pop-

up window.

If you have proxy settings, you need to disable these on your computer.

Because the Router is the gateway for the Internet connection, the computer

does not need any proxy settings to gain access.

Please follow these directions

to verify that you do not have any proxy settings and that the browser you use

is set to connect directly to the LAN.

For Microsoft Internet Explorer 5.0 or higher

A. Click

Start

Settings

, and

Control Panel

. Double-click

Internet Options

Click the

Connections

tab.

Click the

LAN settings

button and remove anything that is checked.

Click the

button to go back to the previous screen.

Click the option

Never dial a connection

This will remove any dial-up

pop-ups for PPPoE users.

For Netscape 4.7 or higher

A. Start

Netscape Navigator

, and click

Edit

Preferences

Advanced

, and

Proxies

Make sure you have

Direct connection to the Internet

selected on this

screen.

Close all the windows to finish.

11. To start over, I need to set the Router to factory default.

Hold the

Reset

button for 10 seconds and then release it. This will return the

password, forwarding, and other settings on the Router to the factory default

settings. In other words, the Router will revert to its original factory configu-

ration.

12. I need to upgrade the firmware.

In order to upgrade the firmware with the latest features, you need to go to the

Linksys website and download the latest firmware at

www.linksys.com

. Follow

these steps:

A. Go to the Linksys website at

http://www.linksys.com

and download the

latest firmware.

B. To upgrade the firmware, follow the steps in the Help section found in

“Chapter 6: The Router’s Web-based Utility.”

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Dual-Band Wireless A+B Broadband Router

• Manually configure the TCP/IP settings with a DNS address provided by

your ISP.

• Make sure that your browser is set to connect directly and that any dial-

up is disabled. For Internet Explorer, click

Tools

Internet Options

, and

then the

Connection

tab. Make sure that Internet Explorer is set to

Never

dial a connection

. For Netscape Navigator, click

Edit

Preferences

Advanced

, and

Proxy

. Make sure that Netscape Navigator is set to

Direct connection to the Internet

18. The Full/Col LED keeps flickering continuously.

• Check the Category 5 Ethernet network cable and its RJ-45 connectors.

• There may be interference with other network devices. Try removing

other PCs or network devices to see if the problem persists. Eliminate

each network device one at a time to determine the cause.

What is the maximum number of IP addresses that the Router will support?

The Router will support up to 253 IP addresses.

Is IPSec Pass-Through supported by the Router?

Yes, it is a built-in feature that the Router automatically enables.

Where is the Router installed on the network?

In a typical environment, the Router is installed between the cable/DSL modem

and the LAN.

Plug the Router into the cable/DSL modem’s Ethernet port.

Does the Router support IPX or AppleTalk?

No. TCP/IP is the only protocol standard for the Internet and has become the

global standard for communications. IPX, a NetWare communications protocol

used only to route messages from one node to another, and AppleTalk, a com-

munications protocol used on Apple and Macintosh networks, can be used for

LAN to LAN connections, but those protocols cannot connect from the Internet

to a LAN.

Does the Internet connection of the Router support 100Mbps Ethernet?

The Router’s current hardware design supports up to 100Mbps Ethernet on its

Internet port; however, the Internet connection speed will vary depending on

the speed of your broadband connection. The Router also supports 100Mbps

over the auto-sensing Fast Ethernet 10/100 switch on the LAN side of the

Router.

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15. I can’t access my e-mail, web, or VPN, or I am getting corrupted data from the

Internet.

The Maximum Transmission Unit (MTU) setting may need to be adjusted. By

default, the MTU is set at 1500.

For most DSL users, it is strongly recom-

mended to use MTU 1492.

If you are having some difficulties, perform the fol-

lowing steps:

A. To connect to the Router, go to the web browser, and enter

http://192.168.1.1

or the

IP address

of the Router.

Enter the password, if asked. (The default password is

admin

Click the

Advanced => Filters

tab.

Look for the MTU option, and select

Enable

. In the

Size

field, enter

1492

Click the

Apply

button to continue.

If your difficulties continue, change the Size to different values. Try this list of

values, one value at a time, in this order, until your problem is solved:

1462

1400

1362

1300

16. The Diag LED stays lit continuously.

• The Diag LED lights up when the device is first powered up. Meantime,

the system will boot up itself and check for proper operation. After fin-

ishing the checking procedure, the LED turns off to show that the system

is working fine. If the LED remains lit after this time, the device is not

working properly. Try to flash the firmware by assigning a static IP

address to the computer, and then upgrade the firmware. Try using the

following settings, IP Address: 192.168.1.50 and Subnet Mask:

255.255.255.0.

17. When I enter a URL or IP address, I get a time-out error or am prompted to retry.

• Check if other PCs work. If they do, ensure that your workstation’s IP set-

tings are correct (IP Address, Subnet Mask, Default Gateway, and DNS).

Restart the computer that is having a problem.

• If the PCs are configured correctly, but still not working, check the

Router. Ensure that it is connected and powered on. Connect to it and

check its settings. (If you cannot connect to it, check the LAN and power

connections.)

• If the Router is configured correctly, check your Internet connection

(DSL/cable modem, etc.) to see if it is working correctly. You can remove

the Router to verify a direct connection.

Frequently Asked Questions

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Dual-Band Wireless A+B Broadband Router

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same CD key connect at the same time, even if on the same LAN (not a prob-

lem with 1.0.1.3).

As far as hosting games, the HL server does not need to be

in the DMZ. Just forward port 27015 to the local IP address of the server com-

puter.

How can I block corrupted FTP downloads?

If you are experiencing corrupted files when you download a file with your FTP

client, try using another FTP program.

The web page hangs; downloads are corrupt, or nothing but junk characters are

being displayed on the screen. What do I need to do?

Force your Ethernet adapter to 10Mbps or half duplex mode, and turn off the

“Auto-negotiate” feature of your Ethernet adapter as a temporary measure.

(Please look at the Network Control Panel in your Ethernet adapter’s Advanced

Properties tab.) Make sure that your proxy setting is disabled in the browser.

Check our website at

www.linksys.com

for more information.

If all else fails in the installation, what can I do?

Reset the Router by holding down the reset button until the Diag LED fully

turns on and off. Reset your cable or DSL modem by powering the unit off and

then on.

Obtain and flash the latest firmware release that is readily available

on the Linksys website,

www.linksys.com

How will I be notified of new Router firmware upgrades?

All Linksys firmware upgrades are posted on the Linksys website at

www.linksys.com

, where they can be downloaded for free. To upgrade the

Router’s firmware, use the Help tab of the Router’s web-based utility. If the

Router’s Internet connection is working well, there is no need to download a

newer firmware version, unless that version contains new features that you

would like to use.

Downloading a more current version of Router firmware

will not enhance the quality or speed of your Internet connection, and may dis-

rupt your current connection stability.

Will the Router function in a Macintosh environment?

Yes, but the Router’s setup pages are accessible only through Internet Explorer

4.0 or Netscape Navigator 4.0 or higher for Macintosh.

I am not able to get the web configuration screen for the Router.

What can I do?

You may have to remove the proxy settings on your Internet browser, e.g.,

Netscape Navigator or Internet Explorer.

Or remove the dial-up settings on

your browser.

Check with your browser documentation, and make sure that

What is

Network Address Translation

and what is it used for?

Network Address Translation (NAT) translates multiple IP addresses on the pri-

vate LAN to one public address that is sent out to the Internet. This adds a level

of security since the address of a PC connected to the private LAN is never

transmitted on the Internet. Furthermore, NAT allows the Router to be used

with low cost Internet accounts, such as DSL or cable modems, when only one

TCP/IP address is provided by the ISP. The user may have many private

addresses behind this single address provided by the ISP.

Does the Router support any operating system other than Windows 95, Windows

98, Windows Millennium, Windows 2000, Windows NT, or Windows XP?

Yes, but Linksys does not, at this time, provide technical support for setup, con-

figuration or troubleshooting of any non-Windows operating systems.

Does the Router support ICQ send file?

Yes, with the following fix: click

ICQ menu -> preference -> connections

tab->

, and check

I am behind a firewall or proxy

. Then set the firewall time-

out to

seconds in the firewall setting. The Internet user can then send a file

to a user behind the Router.

I set up an Unreal Tournament Server, but others on the LAN cannot join. What do

I need to do?

If you have a dedicated Unreal Tournament server running, you need to create

a static IP for each of the LAN computers and forward ports 7777, 7778, 7779,

7780, 7781, and 27900 to the IP address of the server. You can also use a port

forwarding range of 7777 ~ 27900. If you want to use the UT Server Admin,

forward another port. (Port 8080 usually works well but is used for remote

admin. You may have to disable this.) Then in the [UWeb.WebServer] section

of the server.ini file, set the ListenPort to 8080 (to match the mapped port

above) and ServerName to the IP assigned to the Router from your ISP.

Can multiple gamers on the LAN get on one game server and play simultaneously

with just one public IP address?

It depends on which network game or what kind of game server you are using.

For example, Unreal Tournament supports multi-login with one public IP.

How do I get

Half-Life: Team Fortress

to work with the Router?

The default client port for Half-Life is 27005.

The computers on your LAN

need to have “+clientport 2700x” added to the HL shortcut command line; the

x would be 6, 7, 8, and on up. This lets multiple computers connect to the same

server.

One problem:

Version 1.0.1.6 won’t let multiple computers with the

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Dual-Band Wireless A+B Broadband Router

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will work through the Router; however, simultaneous IPSec sessions

may

possible, depending on the specifics of your VPNs.

How can I check whether I have static or DHCP IP Addresses?

Consult your ISP to obtain this information.

How do I get mIRC to work with the Router?

Under the Port Forwarding tab, set port forwarding to 113 for the PC on which

you are using mIRC.

Can the Router act as my DHCP server?

Yes. The Router has DHCP server software built-in.

Can I run an application from a remote computer over the wireless network?

This will depend on whether or not the application is designed to be used over

a network. Consult the application’s documentation to determine if it supports

operation over a network.

What is the IEEE 802.11a standard?

It is one of the IEEE standards for wireless networks. The 802.11a standard

allows wireless networking hardware from different manufacturers to commu-

nicate, provided that the hardware complies with the 802.11a standard. The

802.11a standard states a maximum data transfer rate of 54Mbps and an oper-

ating frequency of 5GHz.

What is the IEEE 802.11b standard?

It is one of the IEEE standards for wireless networks. The 802.11b standard

allows wireless networking hardware from different manufacturers to commu-

nicate, provided that the hardware complies with the 802.11b standard. The

802.11b standard states a maximum data transfer rate of 11Mbps and an oper-

ating frequency of 2.4GHz.

What IEEE 802.11a features are supported?

The product supports the following IEEE 802.11a functions:

•

OFDM protocol

•

Multi-Channel Roaming

•

Automatic Rate Selection

•

RTS/CTS feature

•

Fragmentation

your browser is set to connect directly and that any dial-up is disabled. Make

sure that your browser is set to connect directly and that any dial-up is disabled.

For Internet Explorer, click

Tools

Internet Options

, and then the

Connection

tab. Make sure that Internet Explorer is set to

Never dial a connection

. For

Netscape Navigator, click

Edit

Preferences

Advanced

, and

Proxy

. Make

sure that Netscape Navigator is set to

Direct connection to the Internet

What is DMZ Hosting?

Demilitarized Zone (DMZ) allows one IP address (computer) to be exposed to

the Internet. Some applications require multiple TCP/IP ports to be open.

It is

recommended that you set your computer with a static IP if you want to use

DMZ Hosting. To get the LAN IP address, see “Appendix D: Finding the MAC

Address and IP Address for Your Ethernet Adapter.”

If DMZ Hosting is used, does the exposed user share the public IP with the Router?

No.

Does the Router pass PPTP packets or actively route PPTP sessions?

The Router allows PPTP packets to pass through.

Is the Router cross-platform compatible?

Any platform that supports Ethernet and TCP/IP is compatible with the Router.

How many ports can be simultaneously forwarded?

Theoretically, the Router can establish 520 sessions at the same time, but you

can only forward 10 ranges of ports.

Does the Router replace a modem?

Is there a cable or DSL modem in the Router?

No, the Router must work in conjunction with a cable or DSL modem.

Which modems are compatible with the Router?

The Router is compatible with virtually any cable or DSL modem that supports

Ethernet.

What are the advanced features of the Router?

The Router’s advanced features include Advanced Wireless settings, Filtering,

Port Forwarding, Routing, DMZ Hosting, and MAC Address Cloning.

What is the maximum number of VPN sessions allowed by the Router?

The maximum number depends on many factors. At least one IPSec session

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Dual-Band Wireless A+B Broadband Router

from its original access point, it undertakes a new search. Upon finding a new

access point, it then re-registers, and the communication process continues.

What is ISM band?

The FCC and their counterparts outside of the U.S. have set aside bandwidth

for unlicensed use in the ISM (Industrial, Scientific and Medical) band.

Spectrum in the vicinity of 2.4 GHz, in particular, is being made available

worldwide. This presents a truly revolutionary opportunity to place convenient

high-speed wireless capabilities in the hands of users around the globe.

What is Spread Spectrum?

Spread Spectrum technology is a wideband radio frequency technique devel-

oped by the military for use in reliable, secure, mission-critical communica-

tions systems. It is designed to trade off bandwidth efficiency for reliability,

integrity, and security. In other words, more bandwidth is consumed than in the

case of narrowband transmission, but the trade-off produces a signal that is, in

effect, louder and thus easier to detect, provided that the receiver knows the

parameters of the spread-spectrum signal being broadcast. If a receiver is not

tuned to the right frequency, a spread-spectrum signal looks like background

noise. There are two main alternatives, Direct Sequence Spread Spectrum

(DSSS) and Frequency Hopping Spread Spectrum (FHSS).

What is DSSS? What is FHSS? And what are their differences?

Frequency-Hopping Spread-Spectrum (FHSS) uses a narrowband carrier that

changes frequency in a pattern that is known to both transmitter and receiver.

Properly synchronized, the net effect is to maintain a single logical channel. To

an unintended receiver, FHSS appears to be short-duration impulse noise.

Direct-Sequence Spread-Spectrum (DSSS) generates a redundant bit pattern

for each bit to be transmitted. This bit pattern is called a chip (or chipping

code). The longer the chip, the greater the probability that the original data can

be recovered. Even if one or more bits in the chip are damaged during trans-

mission, statistical techniques embedded in the radio can recover the original

data without the need for retransmission. To an unintended receiver, DSSS

appears as low power wideband noise and is rejected (ignored) by most nar-

rowband receivers.

Will the information be intercepted while it is being transmitted through the air?

WLAN features two-fold protection in security. On the hardware side, as with

Direct Sequence Spread Spectrum technology, it has the inherent security fea-

ture of scrambling. On the software side, WLAN offers the encryption function

(WEP) to enhance security and access control.

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What IEEE 802.11b features are supported?

The product supports the following IEEE 802.11b functions:

•

CSMA/CA plus Acknowledge protocol

•

Multi-Channel Roaming

•

Automatic Rate Selection

•

RTS/CTS feature

•

Fragmentation

•

Power Management

What is ad-hoc mode?

When a wireless network is set to ad-hoc mode, the wireless-equipped com-

puters are configured to communicate directly with each other. The ad-hoc

wireless network will not communicate with any wired network.

What is infrastructure mode?

When a wireless network is set to infrastructure mode, the wireless network is

configured to communicate with a wired network through a wireless access

point.

What is roaming?

Roaming is the ability of a portable computer user to communicate continu-

ously while moving freely throughout an area greater than that covered by a sin-

gle access point. Before using the roaming function, the workstation must make

sure that it is the same channel number with the access point of dedicated cov-

erage area.

To achieve true seamless connectivity, the wireless LAN must incorporate a

number of different functions. Each node and access point, for example, must

always acknowledge receipt of each message. Each node must maintain contact

with the wireless network even when not actually transmitting data. Achieving

these functions simultaneously requires a dynamic RF networking technology

that links access points and nodes. In such a system, the user’s end node under-

takes a search for the best possible access to the system. First, it evaluates such

factors as signal strength and quality, as well as the message load currently

being carried by each access point and the distance of each access point to the

wired backbone. Based on that information, the node next selects the right

access point and registers its address. Communications between end node and

host computer can then be transmitted up and down the backbone.

As the user moves on, the end node’s RF transmitter regularly checks the sys-

tem to determine whether it is in touch with the original access point or whether

it should seek a new one. When a node no longer receives acknowledgment

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