Linksys WRT51AB manual Features, Router’s Functions, IP Addresses, What’s an IP Address?

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Instant Wireless® Series

Features

Compatibility with 802.11a (5GHz) and 802.11b (2.4GHz) Standards

Built-in, 4-Port, 10/100 Switch Supports Wired Ethernet Clients

All Ethernet Ports Support Auto-MDI/MDI-X—No Need for Crossover Cables

Unsurpassed Security Using 802.1x Authentication with up to 152-bit WEP Encryption

Enhanced Security Management Functions: Port Filtering, MAC and IP Address Filtering, DMZ Hosting, and NAT Technology

Access Your Corporate Network Remotely through Virtual Private Networking (VPN)—Supports IPSec and PPTP Pass-Through

Easily Configurable through a Web Browser—Locally and over the Internet

DHCP Server Capability to Assign IP Addresses Automatically

Supports Static and Dynamic Routing (RIP1 and 2)

Free Technical Support—24 Hours a Day, 7 Days a Week, Toll-Free US Calls

1-Year Limited Warranty

The Router’s Functions

Simply put, a router is a network device that connects two networks together.

In this instance, 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 NAT feature protects your network of PCs so users on the public, Internet side cannot “see” your PCs. This is how your network remains private. The Router protects your network by inspecting every packet coming in through the Internet port before delivery to the appropriate PC on your net- work. 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.

Remember that the Router’s ports connect to two sides. The 10/100 LAN ports connect to the LAN, and the Internet port connects to the Internet. The LAN ports transmit data at 10 Mbps or 100 Mbps, and the broadband port, or Internet port, transmits data at 10/100 Mbps.

Dual-Band Wireless A+B Broadband Router

IP Addresses

What’s an IP Address?

IP stands for Internet Protocol. Every device on 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 an IP address to your network devices. You can assign static IP addresses or use the Router to assign IP addresses dynamically.

Note: Since the Router is a device that connects two networks, it needs two IP addresses—one for the LAN, and one for the Internet. In this User Guide, you’ll see references to the “Internet IP address” and the “LAN IP address.”

Since the Router uses NAT technology, the only IP address that can be seen from the Internet for your network is the Router’s Internet IP address.

However, even this Internet IP address can be blocked, so that the Router and network seem invisible to the Internet—see the Block WAN Requests description under Filters in “Chapter 6: The Router’s Web-based Utility.”

Static IP Addresses

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 must be unique and 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 that information from your ISP.

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Contents Dual-Band Wireless A+B Broadband Router Copyright & Trademarks Table of Contents Environmental 127 Common Problems and Solutions Frequently Asked QuestionsIntroduction Router’s Functions FeaturesIP Addresses What’s an IP Address?Dynamic IP Addresses Dhcp Dynamic Host Configuration Protocol ServersRouter Setup Overview Router’s Front Panel LEDs Getting to Know the Dual-Band Wireless A+B Broadband RouterRouter’s Back Panel Proceed to Connect the Router LAN IndicatorsInternet Indicators Overview Wired Connection to a PCConnect the Router Wireless Connection to a PC Configure the PCsGo to Configure the Router’s Basic Settings Configuring Windows 98 and Millennium PCsConfiguring Windows 2000 PCs Configuring Windows XP PCs Configure the Router’s Basic Settings Enter the Default Gateway Automatic Configuration DhcpStatic or Fixed IP Address Enter the Internet IP AddressRouter’s Web-based Utility How to Access the Web-based UtilitySetup Automatic Configuration DhcpStatic IP Pptp 5GHz, 802.11a 5GHz, 802.11a WEP 4GHz, 802.11b WEP Status PasswordLAN Dhcp Help LogAdvanced Tabs 5GHz, 802.11a Advanced Wireless802.1x Configuration Radius Server Filters 11-20 , 21-30 , 31-40 , or 41-50 from Private MAC Filter To set up a filterPrivate IP Filter Port Forwarding Applications External Port TCP Protocol UDP ProtocolClick the Delete This Entry button RoutingDMZ Host MAC Address Clone Common Problems and Solutions Appendix a TroubleshootingNeed to set a static IP address on a PC For Windows NTFor Windows 98, Me, 2000, and XP For Windows XPWant to test my Internet connection TCP UDP Need to set up a server behind my RouterCan’t get the Internet game, server, or application to work Need to upgrade the firmware To start over, I need to set the Router to factory defaultFirmware upgrade failed, and/or the Diag LED is flashing My DSL service’s PPPoE is always disconnectingClick the Advanced = Filters tab Frequently Asked QuestionsHow can I block corrupted FTP downloads? Does the Router support ICQ send file?What are the advanced features of the Router? What is DMZ Hosting?What is the Ieee 802.11a standard? What is the Ieee 802.11b standard?What is ad-hoc mode? What Ieee 802.11b features are supported?What is infrastructure mode? What is roaming?What is a MAC Address? What is WEP?How do I reset the Router? How do I resolve issues with signal loss?Step One Pinging an IP Address Appendix B How to Ping Your ISP’s E-mail & Web AddressesBackground Appendix C Configuring Wireless SecurityStep Two Pinging for a Web Address WEP Encryption 802.1x AuthenticationFigure C-2 MD5 Authentication for Windows XPFigure C-5 Figure C-9 Digital Certificate InstallationFigure C-13 Click Install this certificateFigure C-18 TLS Authentication for Windows XPFigure C-21 For Windows 95, 98, and Me Figure C-25For Windows NT, 2000, and XP Figure D-3Appendix E Glossary 111 113 115 117 119 121 123 125 One 10/100 RJ-45 Port for Cable/DSL Modem Appendix F SpecificationsCategory 5 Ethernet Network Cable or better EnvironmentalSales Information Technical Support RMA Issues Fax Appendix G Warranty InformationAppendix H Contact Information Web site FTP siteCopyright 2002 Linksys, All Rights Reserved