NETGEAR CG814M Internet Security and Firewalls, Domain Name Server, IP Configuration by Dhcp

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Reference Manual for the Model CG814M Wireless Cable Modem Gateway

Domain Name Server

Many of the resources on the Internet can be addressed by simple descriptive names such as www.NETGEAR.com. This addressing is very helpful at the application level, but the descriptive name must be translated to an IP address in order for a user to actually contact the resource. Just as a telephone directory maps names to phone numbers, or as an ARP table maps IP addresses to MAC addresses, a domain name system (DNS) server maps descriptive names of network resources to IP addresses.

When a PC accesses a resource by its descriptive name, it first contacts a DNS server to obtain the IP address of the resource. The PC sends the desired message using the IP address. Many large organizations, such as ISPs, maintain their own DNS servers and allow their customers to use the servers to look up addresses.

IP Configuration by DHCP

When an IP-based local area network is installed, each PC must be configured with an IP address. If the PCs need to access the Internet, they should also be configured with a gateway address and one or more DNS server addresses. As an alternative to manual configuration, there is a method by which each PC on the network can automatically obtain this configuration information. A device on the network may act as a Dynamic Host Configuration Protocol (DHCP) server. The DHCP server stores a list or pool of IP addresses, along with other information (such as gateway and DNS addresses) that it may assign to the other devices on the network. The CG814M Gateway has the capacity to act as a DHCP server.

The CG814M Gateway also functions as a DHCP client when connecting to the ISP. The gateway can automatically obtain an IP address, subnet mask, DNS server addresses, and a gateway address if the ISP provides this information by DHCP.

Internet Security and Firewalls

When your LAN connects to the Internet through a router, an opportunity is created for outsiders to access or disrupt your network. A NAT router provides some protection because by the very nature of the Network Address Translation (NAT) process, the network behind the NAT router is shielded from access by outsiders on the Internet. However, there are methods by which a determined hacker can possibly obtain information about your network or at the least can disrupt your Internet access. A greater degree of protection is provided by a firewall router.

B-10

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 Typographical Conventions About This ManualAudience Special Message Formats Technical SupportKey Features Chapter IntroductionAbout the CG814M Gateway Built-in Cable Modem802.11b Standards-based Wireless Networking Powerful, True FirewallContent Filtering Protocol Support Configurable Auto Uplink Ethernet ConnectionUSB Port 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 RequirementsWhere Do I Get the Internet Configuration Parameters? LAN Configuration RequirementsInternet Configuration Requirements 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 Security Chapter Wireless ConfigurationConsiderations For a Wireless Network Wireless Settings Placement and RangeWireless Settings Restricting Wireless Access by MAC AddressConfiguring Wired Equivalent Privacy WEP Wireless Configuration Wireless Configuration Chapter Protecting Your Network Protecting Access to Your CG814M GatewayChanging the Built-In Password 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 screenCurrent System Time Configuring LAN IP SettingsLAN IP Setup 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 FunctionsLocal Link LEDs Not On Power LED Not OnTest LED Stays On Troubleshooting the Web Configuration Interface Cable Link LED Not OnTesting the LAN Path to Your Gateway Troubleshooting the ISP ConnectionTroubleshooting a TCP/IP Network Using a Ping Utility 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 ConceptsIP Addresses and the Internet What is a Router?Routing Information Protocol 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 DocumentsDomain Name Server IP Configuration by DhcpInternet Security and Firewalls Stateful Packet Inspection What is a Firewall?Denial of Service Attack 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