NETGEAR CG814M manual Netmask Notation Translation Table for One Octet

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Reference Manual for the Model CG814M Wireless Cable Modem Gateway

Although the preceding example uses the entire third octet for a subnet address, note that you are not restricted to octet boundaries in subnetting. To create more network numbers, you need only shift some bits from the host address to the network address. For instance, to partition a Class C network number (192.68.135.0) into two, you shift one bit from the host address to the network address. The new netmask (or subnet mask) is 255.255.255.128. The first subnet has network number 192.68.135.0 with hosts 192.68.135.1 to 129.68.135.126, and the second subnet has network number 192.68.135.128 with hosts 192.68.135.129 to 192.68.135.254.

Note: The number 192.68.135.127 is not assigned because it is the broadcast address of the first subnet. The number 192.68.135.128 is not assigned because it is the network address of the second subnet.

The following table lists the additional subnet mask bits in dotted-decimal notation. To use the table, write down the original class netmask and replace the 0 value octets with the dotted-decimal value of the additional subnet bits. For example, to partition your Class C network with subnet mask 255.255.255.0 into 16 subnets (4 bits), the new subnet mask becomes 255.255.255.240.

Table 6-1. Netmask Notation Translation Table for One Octet

Number of Bits

Dotted-Decimal Value

1128

2192

3224

4240

5248

6252

7254

8255

The following table displays several common netmask values in both the dotted-decimal and the mask length formats.

Table 6-2. Netmask Formats

Dotted-Decimal Masklength

255.0.0.0/8

255.255.0.0/16

B-6	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 Audience About This ManualTypographical Conventions Special Message Formats Technical SupportKey Features Chapter IntroductionAbout the CG814M Gateway Built-in Cable ModemContent Filtering Powerful, True Firewall802.11b Standards-based Wireless Networking USB Port Configurable Auto Uplink Ethernet ConnectionProtocol 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 RequirementsInternet Configuration Requirements LAN 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 Considerations For a Wireless Network Chapter Wireless ConfigurationSecurity Wireless Settings Placement and RangeWireless Settings Restricting Wireless Access by MAC AddressConfiguring Wired Equivalent Privacy WEP Wireless Configuration Wireless Configuration Changing the Built-In Password Protecting Access to Your CG814M GatewayChapter 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 screenLAN IP Setup Configuring LAN IP SettingsCurrent 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 FunctionsTest LED Stays On Power LED Not OnLocal Link LEDs Not On Troubleshooting the Web Configuration Interface Cable Link LED Not OnTroubleshooting a TCP/IP Network Using a Ping Utility Troubleshooting the ISP ConnectionTesting 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 ConceptsRouting Information Protocol What is a Router?IP 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 DocumentsInternet Security and Firewalls IP Configuration by DhcpDomain Name Server Denial of Service Attack What is a Firewall?Stateful 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