Linksys RT41-BU User manual

A Division of Cisco Systems, Inc.
®
Model No.
Wired Broadband Router
RT41-BU
User Guide

Wired Broadband Router
Copyright and Trademarks
Specifications are subject to change without notice. Linksys is a registered trademark or trademark of Cisco
Systems, Inc. and/or its affiliates in the U.S. and certain other countries. Copyright © 2005 Cisco Systems, Inc. All
rights reserved. Other brands and product names are trademarks or registered trademarks of their respective
holders.
How to Use this Guide
Your guide to the Wired Broadband Router has been designed to make understanding networking with the Router
easier than ever. Look for the following items when reading this User Guide:
In addition to these symbols, there are definitions for technical terms that are presented like this:
Also, each figure (diagram, screenshot, or other image) is provided with a figure number and description, like
this:
Figure numbers and descriptions can also be found in the “List of Figures” section.
This exclamation point means there is a caution or
warning and is something that could damage your
property or the Router.
word: definition.
This checkmark means there is a note of interest and
is something you should pay special attention to while
using the Router.
This question mark provides you with a reminder about
something you might need to do while using the Router.
Figure 0-1: Sample Figure Description
RT41-BU-UG-50929NC BW
WARNING: This product contains chemicals, including lead, known
to the State of California to cause cancer, and birth defects or other
reproductive harm. Wash hands after handling.

Wired Broadband Router
TableofContents
Chapter 1: Introduction 1
Welcome 1
What’s in this Guide? 2
Chapter 2: Networking Basics 4
An Introduction to Local Area Networks 4
The Use of IP Addresses 4
Chapter 3: Getting to Know the Router 6
The Back Panel 6
The Front Panel 7
Chapter 4: Connecting the Router 8
Overview 8
Connecting the Router to Your Broadband Modem 8
Chapter 5: Configuring the Router 9
Overview 9
How to Access the Web-based Utility 11
The Setup Tab - Basic Setup 11
The Setup Tab - DDNS 16
The Setup Tab - MAC Address Clone 17
The Security Tab - Firewall 18
The Security Tab - VPN 19
The Access Restrictions Tab - Internet Access 20
The Applications & Gaming Tab - Port Range Forward 22
The Applications & Gaming Tab - Port Trigger 23
The Applications & Gaming Tab - UPnP Forward 24
The Applications & Gaming Tab - DMZ 26
The Administration Tab - Management 27
The Administration Tab - Log 29
The Administration Tab - Diagnostics 30
The Administration Tab - Factory Defaults 31
The Administration Tab - Firmware Upgrade 32
The Administration Tab - Backup and Restore 33
The Administration Tab - Reboot 33

Wired Broadband Router
The Status Tab - Router 34
The Status Tab - Local Network 35
Appendix A: Troubleshooting 36
Common Problems and Solutions 36
Frequently Asked Questions 45
Appendix B: Finding the MAC Address and IP Address for Your Ethernet Adapter 49
Windows 98 or Me Instructions 49
Windows 2000 or XP Instructions 49
For the Router’s Web-based Utility 50
Appendix C: Windows Help 51
Appendix D: Glossary 52
Appendix E: Specifications 57
Appendix F: Warranty Information 58
Appendix G: Regulatory Information 59
Appendix H: Contact Information 65

Wired Broadband Router
ListofFigures
Figure 3-1: Back Panel 6
Figure 3-2: Front Panel 7
Figure 4-1: Connect the Broadband Modem 8
Figure 4-2: Connect a PC 8
Figure 4-3: Connect the Power 8
Figure 5-1: Router’s IP Address 11
Figure 5-2: Router Login 11
Figure 5-3: Setup Tab - Basic Setup(Automatic Configuration - DHCP) 11
Figure 5-4: Static IP 12
Figure 5-5: PPPoE 12
Figure 5-6: PPTP 13
Figure 5-7: Setup Tab - DDNS (DynDNS.org) 16
Figure 5-8: Setup Tab - DDNS (TZO.com) 16
Figure 5-9: Setup Tab - MAC Address Clone 17
Figure 5-10: Security Tab - Firewall 18
Figure 5-11: Security Tab - VPN Passthrough 19
Figure 5-12: Access Restrictions Tab - Internet Access 20
Figure 5-13: Internet Policy Summary 20
Figure 5-14: List of PCs 21
Figure 5-15: Applications & Gaming Tab - Port Range Forward 22
Figure 5-16: Applications & Gaming Tab - Port Trigger 23
Figure 5-17: Applications & Gaming Tab - UPnP Forward 24
Figure 5-18: Applications & Gaming Tab - DMZ 26
Figure 5-19: Administration Tab - Management 27
Figure 5-20: Administration Tab - Log 29
Figure 5-21: Incoming Log Table 29
Figure 5-22: Outgoing Log Table 29
Figure 5-23: Administration Tab - Diagnostics 30

Wired Broadband Router
Figure 5-24: Ping Test 30
Figure 5-25: Traceroute Test 30
Figure 5-26: Administration Tab - Factory Defaults 31
Figure 5-27: Administration Tab - Firmware Upgrade 32
Figure 5-28: Administration Tab - Backup and Restore 33
Figure 5-29: Administration Tab - Reboot 33
Figure 5-30: Status Tab - Router 34
Figure 5-31: Status Tab - Local Network 35
Figure 5-32: DHCP Clients Table 35
Figure B-1: IP Configuration Screen 49
Figure B-2: MAC Address/Adapter Address 49
Figure B-3: MAC Address/Physical Address 50
Figure B-4: Access Restrictions - MAC and IP Addresses 50
Figure B-5: MAC Address Clone 50

1
Chapter 1: Introduction
Welcome
Wired Broadband Router
Chapter1:Introduction
Welcome
Thank you for choosing the Wired Broadband Router. This Router will allow your computers to share a high-speed
Internet connection as well as resources, including files and printers.
How does the Router do all of this? By connecting your computers and peripherals to the Router and connecting
the Router to your cable or DSL modem, the Router can direct and control communications for your network. The
Router’s built-in 4-port switch lets you attach four local PCs, or add more hubs and switches as your network
grows. Auto MDI/MDI-X cross-over detection means you don't have to worry about the cable type.
But what does all of this mean? Networks are useful tools for sharing Internet access and computer resources.
Multiple computers can share Internet access, so you don’t need more than one high-speed Internet connection.
Plus, you can access one printer from different computers and access data located on another computer’s hard
drive. Networks are even used for playing multiplayer video games. So, networks not only are useful in homes
and offices, but also can be fun.
PCs on a wired network create a LAN, or Local Area Network. They are connected with Ethernet cables, which is
why the network is called “wired”.
To create your network, install and set up the Router. To guide you through the process, Linksys strongly
recommends that you run the Setup Wizard on the Setup CD-ROM. If you prefer to manually set up the Router, use
the instructions in this User Guide to help you. These instructions should be all you need to get the most out of
the Router.
ethernet: an IEEE standard network protocol
that specifies how data is placed on and
retrieved from a common transmission
medium.
lan (local area network): the computers and
networking products that make up the network
in your home or office.

2
Chapter 1: Introduction
What’s in this Guide?
Wired Broadband Router
What’s in this Guide?
This user guide covers the basic steps for setting up a network with a router. After going through “Chapter 3:
Getting to Know the Router,” most users will only need to use the following chapters:
• Chapter 4: Connecting the Router
This chapter instructs you on how to connect the Router to your cable or DSL modem and PCs.
• Chapter 5: Configuring the Router
This chapter explains how to configure the Router using your web browser and the Router’s Web-based
Utility. You will configure the Router using the settings provided by your ISP.
When you’re finished with the basic steps, then you are ready to connect to the Internet.
You also have other chapter available for reference:
• Chapter 1: Introduction
This chapter describes the Router’s applications and this User Guide.
• Chapter 2: Networking Basics
This chapter briefly explains how a network functions.
• Appendix A: Troubleshooting
This appendix describes some possible problems and solutions, as well as frequently asked questions,
regarding installation and use of the Router.
• Appendix B: Finding the MAC Address and IP Address for Your Ethernet Adapter
This appendix instructs you on how to find the MAC address or Ethernet address of your PC’s Ethernet
network adapter.
• Appendix C: Windows Help
This appendix describes how you can use Windows Help for instructions about networking, such as installing
the TCP/IP protocol.
• Appendix D: Glossary
This appendix gives a brief glossary of terms frequently used in networking.
• Appendix E: Specifications
This appendix provides the technical specifications for the Router.
• Appendix F: Warranty Information
This appendix supplies the warranty information for the Router.

3
Chapter 1: Introduction
What’s in this Guide?
Wired Broadband Router
• Appendix G: Regulatory Information
This appendix supplies the regulatory information regarding the Router.
• Appendix H: Contact Information
This appendix provides contact information for a variety of Linksys resources, including Technical Support.

4
Chapter 2: Networking Basics
An Introduction to Local Area Networks
Wired Broadband Router
Chapter2:NetworkingBasics
An Introduction to Local Area Networks
Simply put, a router is a network device that connects two networks together.
The Router connects your local area network (LAN), or the group of PCs in your home or office, to the Internet. The
Router processes and regulates the data that travels between these two networks.
The Router’s Network Address Translation (NAT) technology protects your network of PCs so users on the Internet
cannot “see” your PCs. This is how your LAN remains private. The Router protects your network by inspecting the
first packet coming in through the Internet port before delivery to the final destination on one of the Ethernet
ports. The Router inspects Internet port services like the web server, ftp server, or other Internet applications,
and, if allowed, it will forward the packet to the appropriate PC on the LAN side.
The Use of IP Addresses
IP stands for Internet Protocol. Every device in an IP-based network, including PCs, print servers, and routers,
requires an IP address to identify its location, or address, on the network. This applies to both the Internet and
LAN connections.
There are two ways of assigning IP addresses to your network devices.
A static IP address is a fixed IP address that you assign manually to a PC or other device on the network. Since a
static IP address remains valid until you disable it, static IP addressing ensures that the device assigned it will
always have that same IP address until you change it. Static IP addresses are commonly used with network
devices such as server PCs or print servers.
If you use the Router to share your cable or DSL Internet connection, contact your ISP to find out if they have
assigned a static IP address to your account. If so, you will need that static IP address when configuring the
Router. You can get the information from your ISP.
A dynamic IP address is automatically assigned to a device on the network. These IP addresses are called
dynamic because they are only temporarily assigned to the PC or other device. After a certain time period, they
expire and may change. If a PC logs onto the network (or the Internet) and its dynamic IP address has expired, the
DHCP server will assign it a new dynamic IP address.
dynamic ip address: a temporary IP
address assigned by a DHCP server.
static ip address: a fixed address
assigned to a computer or device that
is connected to a network.
nat (network address translation): NAT
technology translates IP addresses of a
local area network to a different IP
address for the Internet.
dhcp (dynamic host configuration
protocol): a protocol that lets one
device on a local network, known as a
DHCP server, assign temporary IP
addresses to the other network
devices, typically computers.

5
Chapter 2: Networking Basics
The Use of IP Addresses
Wired Broadband Router
A DHCP server can either be a designated PC on the network or another network device, such as the Router. By
default, the Router’s Internet Connection Type is Obtain an IP automatically (DHCP).
The PC or network device obtaining an IP address is called the DHCP client. DHCP frees you from having to assign
IP addresses manually every time a new user is added to your network.
For DSL users, many ISPs may require you to log on with a user name and password to gain access to the
Internet. This is a dedicated, high-speed connection type called Point to Point Protocol over Ethernet (PPPoE).
PPPoE is similar to a dial-up connection, but PPPoE does not dial a phone number when establishing a
connection. It also will provide the Router with a dynamic IP address to establish a connection to the Internet.
By default, a DHCP server (on the LAN side) is enabled on the Router. If you already have a DHCP server running
on your network, you MUST disable one of the two DHCP servers. If you run more than one DHCP server on your
network, you will experience network errors, such as conflicting IP addresses. To disable DHCP on the Router,
see the Basic Setup section in “Chapter 5: Configuring the Router.”

6
Chapter 3: Getting to Know the Router
The Back Panel
Wired Broadband Router
Chapter3:GettingtoKnowtheRouter
The Back Panel
The Router’s ports and the Reset button are located on the back panel of the Router.
Internet This Internet port connects to your cable or DSL modem.
Ethernet 1-4 These four Ethernet ports connect to network devices, such as PCs, print servers, or
additional switches.
Reset Button There are two ways to reset the Router to its factory default settings. Either press the Reset
button for approximately five seconds, or restore the defaults from the Administration tab -
Factory Defaults of the Router's Web-based Utility.
Power The Power port is where you will connect the power adapter.
Figure 3-1: Back Panel
NOTE: If you use the Reset button, the Router’s
settings will be reset to their factory defaults.

7
Chapter 3: Getting to Know the Router
The Front Panel
Wired Broadband Router
The Front Panel
The Router’s LEDs, which inform you about network activities, are located on the front panel.
Power Green. The Power LED lights up when the Router is powered on. If the LED is flashing, the
Router is booting up or running a system self-test.
Ethernet 1-4 Green. The Ethernet LED serves two purposes. If the LED is solidly lit, the Router is connected
to a device through the corresponding port (Ethernet 1, 2, 3, or 4). If the LED is flashing, the
Router is sending or receiving data over that port.
Internet Green. The Internet LED lights up when the Router is connected to your cable or DSL modem.
If the LED is flashing, the Router is sending or receiving data over the Internet port.
Proceed to “Chapter 4: Connecting the Router.”
Figure 3-2: Front Panel

8
Chapter 4: Connecting the Router
Overview
Wired Broadband Router
Chapter4:ConnectingtheRouter
Overview
This chapter provides instructions to connect the Router to your Broadband Modem.
Connecting the Router to Your Broadband Modem
1. Make sure that all of your hardware is powered off, including the Router, PCs, and broadband modem.
2. Connect your broadband modem’s Ethernet cable to the Router’s Internet port.
3. Connect one end of an Ethernet network cable to one of the numbered ports on the back of the Router.
Connect the other end to an Ethernet port on a network device, e.g., a PC, print server, or switch.
Repeat this step to connect more PCs or other network devices to the Router.
4. Power on the broadband modem.
5. Connect the included power adapter to the Router’s Power port, and then plug the power adapter into an
electrical outlet. The Power LED on the front panel will light up as soon as the Router powers on.
6. Power on your PC(s).
Proceed to “Chapter 5: Configuring the Router.”
Figure 4-1: Connect the Broadband Modem
Figure 4-2: Connect a PC
Figure 4-3: Connect the Power

9
Chapter 5: Configuring the Router
Overview
Wired Broadband Router
Chapter5:ConfiguringtheRouter
Overview
Linksys recommends using the Setup CD-ROM for first-time installation of the Router. If you do not wish to run
the Setup Wizard on the Setup CD-ROM, then you can use the Web-based Utility to configure the Router. For
advanced users, you may configure the Router’s advanced settings through the Web-based Utility.
This chapter will describe each web page on the Utility and each page’s key functions. The Utility can be
accessed via your web browser through use of a computer connected to the Router. For a basic network setup,
most users only have to use the following screens of the Utility:
• Basic Setup. On the Basic Setup screen, enter the Internet connection settings provided by your ISP. If you do
not have this information, you can call your ISP to request the settings. Once you have the setup information
for your specific type of Internet connection, then you can configure the Router.
• Management. Click the Administration tab and then the Management tab. The Router’s default password is
admin. To secure the Router, change the Password from its default.
There are six main tabs: Setup, Security, Access Restrictions, Applications & Gaming, Administration, and Status.
Additional tabs will be available after you click one of the main tabs. For more information, contact linksys at
www.linksys.com.
Setup
• Basic Setup. Enter the Internet connection and network settings on this screen.
• DDNS. Enable the Router’s Dynamic Domain Name System (DDNS) feature on this screen.
• MAC Address Clone. If you need to clone a MAC address onto the Router, use this screen.
Security
• Firewall. On this screen, you can configure a variety of filters to enhance the security of your network.
• VPN. To enable or disable IPSec, PPTP, and/or L2TP Passthrough, use this screen.

10
Chapter 5: Configuring the Router
Overview
Wired Broadband Router
Access Restrictions
Internet Access. This screen allows you to permit or block specific kinds of Internet usage and traffic.
Applications & Gaming
• Port Range Forward. Set up public services or other specialized Internet applications on your network.
• Port Trigger. To set up triggered ranges and forwarded ranges for Internet applications, click this tab.
• UPnP Forward. Use this screen to alter UPnP forwarding settings.
• DMZ. Click this tab to allow one local user to be exposed to the Internet for use of special-purpose services.
Administration
• Management. Alter the Router’s password and access privileges, as well as the SNMP and UPnP settings.
• Log. If you want to view or save activity logs, click this tab.
• Diagnostics. Use this screen to check the connections of your network components.
• Factory Defaults. If you want to restore the Router’s factory defaults, then use this screen.
• Firmware Upgrade. This screen allows you to upgrade the Router’s firmware.
• Backup and Restore. You can back up and restore the Router’s configuration if necessary.
• Reboot. This screen allows you to remotely reboot the Router from your computer.
Status
• Router. This screen provides status information about the Router.
• Local Network. This provides status information about the local network.

11
Chapter 5: Configuring the Router
How to Access the Web-based Utility
Wired Broadband Router
How to Access the Web-based Utility
To access the Web-based Utility of the Router, launch Internet Explorer or Netscape Navigator, and enter the
Router’s default IP address, 192.168.15.1, in the Address field. Press the Enter key.
A screen will appear asking you for your User Name and Password. Leave the User Name field blank, and enter
admin in the User Name and Password fields. Then click the OK button.
Make the necessary changes through the Utility. When you have finished making changes to a screen, click the
Save Settings button to save the changes, or click the Cancel Changes button to undo your changes. For help
information on a tab, click Help.
The Setup Tab - Basic Setup
The Basic Setup screen is the first screen you see when you access the Web-based Utility.
Internet Setup
The Internet Setup section configures the Router for your Internet connection type. This information can be
obtained from your ISP.
Internet Connection Type
The Router supports four connection types: Automatic Configuration - DHCP, Static IP, PPPoE, and PPTP. Each
Basic Setup screen and available features will differ depending on what kind of connection type you select.
Automatic Configuration (DHCP)
By default, the Router’s Internet Connection Type is set to Automatic Configuration (DHCP), and it should be
used only if your ISP supports DHCP or you are connecting through a dynamic IP address.
Figure 5-2: Router Login
Figure 5-1: Router’s IP Address
Figure 5-3: Setup Tab - Basic Setup
(Automatic Configuration - DHCP)

12
Chapter 5: Configuring the Router
The Setup Tab - Basic Setup
Wired Broadband Router
Static IP
If you are required to use a permanent IP address, then select Static IP.
Internet IP Address. This is the IP address that the Router has, when seen from the Internet. Your ISP will
provide you with the IP Address you need to specify here.
Subnet Mask. This is the Router’s Subnet Mask, as seen by external users on the Internet (including your
ISP). Your ISP will provide you with the Subnet Mask.
Default Gateway. Your ISP will provide you with the Default Gateway Address.
Static DNS 1-2. Your ISP will provide you with at least one DNS (Domain Name System) Server IP Address.
PPPoE
Some DSL-based ISPs use PPPoE (Point-to-Point Protocol over Ethernet) to establish Internet connections for
end-users. If you use a DSL line, check with your ISP to see if they use PPPoE. If they do, you will have to
enable it.
User Name and Password. Enter the User Name and Password provided by your ISP.
Connect on Demand and Max Idle Time. You can configure the Router to cut the Internet connection after it
has been inactive for a specific period of time (Max Idle Time). If your Internet connection has been
terminated due to inactivity, Connect on Demand enables the Router to automatically re-establish your
connection as soon as you attempt to access the Internet again. If you wish to activate Connect on Demand,
click the radio button. If you want your Internet connection to remain on at all times, enter 0in the Max Idle
Time field. Otherwise, enter the number of minutes you want to have elapsed before your Internet access
disconnects.
Keep Alive and Redial Period. This option keeps your Internet access connected indefinitely, even when it
sits idle. If you select this option, the Router will periodically check your Internet connection. If the connection
is down, then the Router will automatically re-establish the connection. To use this option, click the radio
button next to Keep Alive. The default Redial Period is 30 seconds.
When you are finished, click the Save Settings button. Then click the Status tab, and click the Connect
button to start the connection.
Figure 5-4: Static IP
Figure 5-5: PPPoE
static ip address: a fixed address
assigned to a computer or device
connected to a network.
pppoe: a type of broadband connection that
provides authentication (username and
password) in addition to data transport
subnet mask: an address code that
determines the size of the network
default gateway: a device that forwards
Internet traffic from your local area network
NOTE: For DSL users, if you need to enable PPPoE support, remember to remove any PPPoE
applications that are installed on your PCs.

13
Chapter 5: Configuring the Router
The Setup Tab - Basic Setup
Wired Broadband Router
PPTP
Point-to-Point Tunneling Protocol (PPTP) is a service that applies to connections in Europe and Israel only.
Internet IP Address. This is the IP address that the Router has, when seen from the Internet. Your ISP will
provide you with the IP Address you need to specify here.
Subnet Mask. This is the Router’s Subnet Mask, as seen by external users on the Internet (including your
ISP). Your ISP will provide you with the Subnet Mask.
Gateway. Your ISP will provide you with the Default Gateway Address.
User Name and Password. Enter the User Name and Password provided by your ISP.
Connect on Demand and Max Idle Time. You can configure the Router to cut the Internet connection after it
has been inactive for a specific period of time (Max Idle Time). If your Internet connection has been
terminated due to inactivity, Connect on Demand enables the Router to automatically re-establish your
connection as soon as you attempt to access the Internet again. If you wish to activate Connect on Demand,
click the radio button. If you want your Internet connection to remain on at all times, enter 0in the Max Idle
Time field. Otherwise, enter the number of minutes you want to have elapsed before your Internet access
disconnects.
Keep Alive and Redial Period. This option keeps your Internet access connected indefinitely, even when it
sits idle. If you select this option, the Router will periodically check your Internet connection. If the connection
is down, then the Router will automatically re-establish the connection. To use this option, click the radio
button next to Keep Alive. The default Redial Period is 30 seconds.
When you are finished, click the Save Settings button. Then click the Status tab, and click the Connect
button to start the connection.
Optional Settings
Some of these settings may be required by your ISP. Verify with your ISP before making any changes.
Router Name. Enter a name for this Router.
Host Name and Domain Name. These fields allow you to supply a host and domain name for the Router. Some
ISPs require these names as identification. You may have to check with your ISP to see if your broadband Internet
service has been configured with a host and domain name. In most cases, leaving these fields blank will work.
MTU. The MTU (Maximum Transmission Unit) setting specifies the largest packet size permitted for network
transmission. The default is Auto. If you want to manually enter a value, select Manual and enter the value
Figure 5-6: PPTP
packet: a unit of data sent over a network

14
Chapter 5: Configuring the Router
The Setup Tab - Basic Setup
Wired Broadband Router
desired. It is recommended that you leave this value in the 1200 to 1500 range. For most DSL users, it is
recommended to use the value 1492. By default, MTU is set at 1500 when disabled.
Internet Port Speed. You can specify the transmission speed of the Router’s Internet port if your broadband
modem requires a specific speed setting. In most cases you should keep the default setting, Auto.
Network Setup
The Network Setup section allows you to change the Router’s local network settings.
Router IP
The values for the Router’s Local IP Address and Subnet Mask are shown here. In most cases, keeping the default
values will work.
Local IP Address. The default value is 192.168.15.1.
Subnet Mask. The default value is 255.255.255.0.
Network Address Server Settings (DHCP)
These settings allow you to configure the Router’s Dynamic Host Configuration Protocol (DHCP) server function.
The Router can be used as a DHCP server for your network. A DHCP server automatically assigns an IP address to
each computer on your network. Unless you already have one, it is highly recommended that you leave the Router
enabled as a DHCP server.
DHCP Server. DHCP is enabled by factory default. If you already have a DHCP server on your network, set the
Router’s DHCP option to Disable. If you disable DHCP, remember to assign a static IP address to the Router.
Starting IP Address. Enter a value for the DHCP server to start with when issuing IP addresses. Because the
default IP address for the Router is 192.168.15.1, the Start IP Address must be 192.168.15. 2 or greater, but
smaller than 192.168.15.254. The default Start IP Address is 192.168.15.100.
Maximum Number of DHCP Users (Optional). Enter the maximum number of PCs that you want the DHCP server
to assign IP addresses to. This number cannot be greater than 253. The default is 50.
Client Lease Time. The Client Lease Time is the amount of time a network user will be allowed connection to the
Router with their current dynamic IP address. Enter the amount of time, in minutes, that the user will be “leased”
this dynamic IP address. After the dynamic IP address has expired, the user will be automatically assigned a new
dynamic IP address. The default is 0minutes, which means one day.
dynamic ip address: a temporary IP
address assigned by a DHCP server