NETGEAR CG814M What is a Router?, Routing Information Protocol, IP Addresses and the Internet

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Reference Manual for the Model CG814M Wireless Cable Modem Gateway

What is a Router?

A router is a device that forwards traffic between networks based on network layer information in the data and on routing tables maintained by the router. In these routing tables, a router builds up a logical picture of the overall network by gathering and exchanging information with other routers in the network. Using this information, the router chooses the best path for forwarding network traffic.

Routers vary in performance and scale, number of routing protocols supported, and types of physical WAN connection they support. The CG814M Wireless Cable Modem Gateway is a small office router that routes the IP protocol over a single-user broadband connection.

Routing Information Protocol

One of the protocols used by a router to build and maintain a picture of the network is the Routing Information Protocol (RIP). Using RIP, routers periodically update one another and check for changes to add to the routing table.

The CG814M Gateway supports both the older RIP-1 and the newer RIP-2 protocols. Among other improvements, RIP-2 supports subnet and multicast protocols. RIP is not required for most home applications.

IP Addresses and the Internet

Because TCP/IP networks are interconnected across the world, every machine on the Internet must have a unique address to make sure that transmitted data reaches the correct destination. Blocks of addresses are assigned to organizations by the Internet Assigned Numbers Authority (IANA).

Individual users and small organizations may obtain their addresses either from the IANA or from an Internet service provider (ISP). You can contact IANA at www.iana.org.

The Internet Protocol (IP) uses a 32-bit address structure. The address is usually written in dot notation (also called dotted-decimal notation), in which each group of eight bits is written in decimal form, separated by decimal points.

For example, the following binary address:

11000011 00100010 00001100 00000111

is normally written as:

195.34.12.7

B-2	Networks, Routing, and Firewall Basics

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Contents NETGEAR, Inc Trademarks World Wide Web Page Contents USB Appendix a Appendix C Contents Contents About This Manual AudienceTypographical Conventions Special Message Formats Technical SupportKey Features Chapter IntroductionAbout the CG814M Gateway Built-in Cable ModemPowerful, True Firewall Content Filtering802.11b Standards-based Wireless Networking Configurable Auto Uplink Ethernet Connection USB PortProtocol Support Easy Installation and Management What’s in the Box? Firewall’s Front PanelLED Descriptions Gateway’s Rear Panel CG814M Gateway Rear PanelIntroduction Connecting the Gateway to the Internet What You Will Need Before You BeginLAN Hardware Requirements Computer RequirementsLAN Configuration Requirements Internet Configuration RequirementsWhere Do I Get the Internet Configuration Parameters? Connecting the Gateway to the Internet Record Your Internet Connection Information Connecting the CG814M Gateway Connecting to Your ComputerEthernet USBConnecting to your Cable Service Provider WirelessConnecting the Power Adapter Log in to the GatewayLogin window opens as shown in -3below Connect to the Internet Connecting the CG814M Gateway to the Internet ConfigurationConnecting the Gateway to the Internet Connecting the Gateway to the Internet Connecting the Gateway to the Internet Chapter Wireless Configuration Considerations For a Wireless NetworkSecurity Wireless Settings Placement and RangeWireless Settings Restricting Wireless Access by MAC AddressConfiguring Wired Equivalent Privacy WEP Wireless Configuration Wireless Configuration Protecting Access to Your CG814M Gateway Changing the Built-In PasswordChapter Protecting Your Network Blocking Keywords, Sites, and Services Set Password menuBlock Keywords and Domains Click on the Block Sites link of the Content Filtering menu Blocking Services ProxyPort Blocking CookiesPort Forwarding Port Blocking menuTo forward inbound traffic Port Triggering Considerations for Port ForwardingTo configure Port Triggering Setting Up a Default DMZ Host Respond to Ping on Internet WAN PortProtecting Your Network Chapter Managing Your Network Network Status InformationViewing Gateway Status This screen shows the following parametersMenu 3.2 Router Status Fields Connection Status Connection screenConfiguring LAN IP Settings LAN IP SetupCurrent System Time Dhcp Use router as Dhcp serverViewing and Emailing Logged Information Logs menuErasing Configuration Enabling Logs Event E-mail NotificationRunning Diagnostic Utilities Diagnostics menuManaging Your Network Chapter Troubleshooting Basic FunctionsPower LED Not On Test LED Stays OnLocal Link LEDs Not On Troubleshooting the Web Configuration Interface Cable Link LED Not OnTroubleshooting the ISP Connection Troubleshooting a TCP/IP Network Using a Ping UtilityTesting the LAN Path to Your Gateway Testing the Path from Your PC to a Remote Device Troubleshooting Appendix a Technical Specifications TCP/IPTechnical Specifications Appendix B Networks, Routing, and Firewall Basics Related Publications Basic Router ConceptsWhat is a Router? Routing Information ProtocolIP Addresses and the Internet Three Main Address Classes Netmask EqualsSubnet Addressing Example of Subnetting a Class B AddressNetmask Notation Translation Table for One Octet Private IP Addresses Single IP Address Operation Using NAT Single IP Address Operation Using NATMAC Addresses and Address Resolution Protocol Related DocumentsIP Configuration by Dhcp Internet Security and FirewallsDomain Name Server What is a Firewall? Denial of Service AttackStateful Packet Inspection Wireless Networking Wireless Network ConfigurationAd-hoc Mode Peer-to-Peer Workgroup Infrastructure ModeExtended Service Set Identification Essid Authentication and WEP EncryptionWireless Channel Selection Table B-1 802.11b Radio Frequency ChannelsUplink Switches and Crossover Cables Ethernet CablingCable Quality Appendix C Preparing Your Network Preparing Your Computers for TCP/IP NetworkingConfiguring Windows 95, 98, and ME for TCP/IP Networking Install or Verify Windows Networking ComponentsPreparing Your Network Enabling Dhcp to Automatically Configure TCP/IP Settings Selecting Windows’ Internet Access MethodConfiguring Windows NT, 2000 or XP for IP Networking Verifying TCP/IP PropertiesConfiguring the Macintosh for TCP/IP Networking MacOS 8.6 orMacOS Verifying TCP/IP Properties for Macintosh Computers What Is Your Configuration Information? Verifying the Readiness of Your Internet AccountMail.xxx.yyy.com Preparing Your Network Restarting the Network Glossary Networks See Network Address Translation Connection