Linksys BEFSX41 manual An Introduction to LANs and WANs, IP Addresses

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Instant Broadband® Series

An Introduction to LANs and WANs

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 Wide Area Network (WAN), that is, the Internet. The Router processes and regulates the data that travels between these two networks.

Think of the Router as a network device with two sides: the first side is made up of your private Local Area Network (LAN) of PCs. The other, public side is the Internet, or the Wide Area Network (WAN), outside of your home or office.

The Router’s firewall (NAT) protects your network of PCs so users on the pub- lic, Internet side cannot “see” your PCs. This is how your LAN, or network, remains private. The Router protects your network by inspecting the first pack- et coming in through the WAN port before delivery to the final destination on the LAN port. 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: your 10/100 LAN ports and the Internet WAN port. The WAN and LAN ports transmit data at 10 Mbps or 100 Mbps.

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 WAN and LAN connections. There are two ways of assigning an IP address to your network devices.

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 are com- monly 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.

EtherFast® Cable/DSL Firewall Router with 4-Port Switch/VPN Endpoint

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

Since the Router has firewall security, the only IP address that can be seen from the Internet for your network is the Router’s WAN IP address.

However, even this WAN IP address for the Router can be blocked, so that the Router and network seem invisible to the Internet—see the Blocking WAN Requests description under Filters in “Chapter 7: The Cable/DSL Firewall Router’s Web-based Utility.”

Dynamic IP Addresses

A dynamic IP address is automatically assigned to a device on the network, such as PCs and print servers. These IP addresses are called “dynamic” because they are only temporarily assigned to the PC or 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.

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 con- nection 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. PPPoE also will provide the Router with a dynamic IP address to establish a connection to the Internet.

DHCP (Dynamic Host Configuration Protocol) Servers

PCs and other network devices using dynamic IP addressing are assigned a new IP address by a DHCP server. 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.

A DHCP server can either be a designated PC on the network or another net- work device, such as the Router. By default, the Router’s WAN setting is DHCP client.

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Contents User Guide Copyright & Trademarks Table of Contents Environmental 139 FeaturesIntroduction IP Addresses An Introduction to LANs and WANsYour Virtual Private Network VPN Network Setup OverviewWhy Do I Need a VPN? Firewall Router to Firewall Router What is a Virtual Private Network?Router’s Back Panel PowerModem connection will not work from any other port PortsProceed to Connect the Router WAN and LAN LEDsRouter’s Front Panel LEDs Router’s hardware installation is now complete Connecting Your Hardware Together and Booting UpConnect the Router OverviewConfiguring Windows 95, 98, and Millennium PCs Configure the PCsConfiguring Windows 2000 PCs Go to Configure the RouterConfiguring Windows XP PCs Configure the Router Static IP Address Obtain an IP Address AutomaticallyAdvanced Proxies. Click Direct Connection to the Internet Enter the Gateway AddressRAS PPPoECable/DSL Firewall Router’s Web-based Utility Quick and Easy Router AdministrationSetup Static IP User Name and PasswordWAN IP Firewall Block WAN Request Remote UpgradeMulticast Pass Through IPSec Pass ThroughVPN Establishing a TunnelLocal Secure Group and Remote Secure Group Remote Security Gateway Key Management AuthenticationEncryption Instant Broadband Series Phase Advanced Settings for Selected IPSec TunnelPassword Other SettingsStatus Dhcp Log Help Filters AdvancedInstant Broadband Series Forwarding UPnP Forwarding Port Triggering Static Routing Dynamic RoutingDMZ Host Address DMZ HostDMZ Port MAC Address Clone Current DMZ HostDdns DynDNS.orgTZO.com Appendix a TroubleshootingCommon Problems and Solutions For Windows 95, 98, and Me For Windows NTFor Windows XP For Windows XP Am not able to access the Router’s web interface Setup Can’t get the Internet game, server, or application to work To start over, I need to set the Router to factory default Need to use port triggering Click the Advanced = Filter tabFrequently Asked Questions TCP/IP is compatible with the Router Appendix B Maximizing VPN Security Environment IntroductionWindows 2000 or Windows XP Step One Create an IPSec PolicyIP Address Filter List 1 win-routerStep Two Build Filter Lists Figure C-6 Filter List 2 router=winTunnel 1 win-router Step Three Configure Individual Tunnel RulesString to Protect Negotiate Security Key exchange pre Respond Using IPSec XYZ12345. ClickShared key, as shown AcceptTunnel 2 router-win Key Exchange Action Require Security This string to protectPreshared key, XYZ12345Step Four Assign New IPSec Policy Figure C-24Figure C-28 Step Five Create a Tunnel Through the Web-based UtilityAppendix D Snmp Functions Appendix E How to Ping Your ISP’s E-mail & Web AddressesFigure E-1 TCP/IP installation is now complete Appendix F Installing the TCP/IP ProtocolFor Windows NT, 2000, and XP Figure G-1Figure G-5 Appendix H Glossary 129 131 133 135 137 Environmental Appendix I SpecificationsAppendix K Contact Information Appendix J Warranty InformationSales Information Web FTP SiteCopyright 2003 Linksys, All Rights Reserved
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