Netopia R7200 Appendix C Understanding Netopia NAT Behavior, Network configuration, Background

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Understanding Netopia NAT Behavior C-1

Appendix C

Understanding Netopia NAT Behavior

The Netopia R7200 implements a powerful feature called Network Address Translation (NAT) as specified in RFC 1631. NAT is used for IP address conservation and for security purposes since there will only be a single IP “presence” on the WAN. This appendix describes the NAT functionality within the Netopia R7200 and provides examples for setup and use.

Network configuration

Below is a diagram of the network referenced in this appendix.

ISP Network

IP: 200.1.1.1

Mask: 255.255.255.0

Router

Internet

WWWServer

IP: 163.176.4.32

Mask: 255.255.255.0

MAC: 00-05-02-0c-1b-41

 

Customer Site

Netopia Router

Netopia Router

WAN IP: 200.1.1.40

LAN IP: 192.168.5.1

Mask: 255.255.255.0

Mask: 255.255.255.240

MAC: 00-00-c5-60-21-0a

MAC: 00-00-c5-60-21-0a

 

Netopia

 

 

 

Workstation A

IP: 192.168.5.2

Mask: 255.255.255.240

MAC: 00-05-02-04-12-4f

Workstation B

IP: 192.168.5.3

Mask: 255.255.255.240

MAC: 00-05-02-00-1e-03

LAN

Background

NAT is a mechanism employed within the Netopia R7200 to acquire a statically or dynamically assigned IP address on its WAN interface and proxy against locally assigned IP addresses on its LAN interface. The Netopia R7200 uses a one-to-many IP address mapping scheme; that is against a single IP address the Netopia R7200 acquires on its WAN interface, the Netopia R7200 can proxy 14, 30, or an unlimited number of IP hosts on the LAN interface.

In order to fully understand how NAT works, you must understand how a PPP connection is established and IP addresses are negotiated.

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Contents Netopia R7200 Sdsl Router Part Number Contents Part II Advanced Configuration Contents Aurp Snmp Xmodem Part III Appendixes User’s Reference Guide Part I Getting Started User’s Reference Guide Overview Features and capabilitiesChapter Introduction How to use this guide Finding an Internet service provider Chapter Setting Up Internet ServicesUnique requirements Setting up a Netopia R7200 account Obtaining an IP addressPricing and support Endorsements Deciding on an ISP accountLocal LAN IP address information to obtain Obtaining information from the ISPWith Network Address Translation Without Network Address TranslationUser’s Reference Guide Find a location Chapter Making the Physical ConnectionsWhat you need Identify the connectors and attach the cablesYour router on Netopia R7200 Sdsl Router back panel portsNetopia R7200 LED front panel Netopia R7200 Sdsl Router status lightsReadying computers on your local network Chapter Connecting to Your Local Area NetworkUser’s Reference Guide Connecting to an Ethernet network 10Base-T Adding an external modem Connecting to a LocalTalk network Chapter Setting up your Router with the SmartStart Wizard Before running SmartStart SmartStart Wizard configuration screens Setting up your Router with the SmartStart WizardEasy option Advanced setupAdvanced option Configuration screen on Configuration tab Dynamic configuration recommendedStatic configuration optional Add. Repeat this process for the secondary DNS TCP/IP Configuring TCP/IP on Macintosh computersTCP/IP or MacTCP Dynamic configuration using MacIP optional Setting up your Router with the SmartStart Wizard User’s Reference Guide Chapter Console-Based Management Connecting through a Telnet session Configuring Telnet software Connecting a console cable to your routerPC ANSI-BBS Navigating through the console screensAccessing the Easy Setup console screens Chapter Easy SetupEasy Setup console screens See Appendix A, Troubleshooting, for more suggestions Quick Easy Setup connection path Main Menu appears Sdsl Line ConfigurationPrevious Screen Next Screen Easy Setup ProfileIP Easy Setup Easy Setup Security Configuration Previous Screen To Main Menu Part II Advanced Configuration User’s Reference Guide WAN configuration Chapter WAN and System ConfigurationATM VPI ATM VCI Creating a new Connection Profile IPX Profile Parameters Remote IPX Network Datalink PPP/MP Options Data Compression Default profile Main Menu Default Profile screen appears IP parameters default profile screen System configuration screens IPX parameters default profile screenNavigating through the system configuration screens System configuration features Filter sets firewalls Network protocols setupIP address serving Date and timeConsole configuration Snmp Simple Network Management Protocol Upgrade feature setSecurity LoggingInstalling the Syslog client User’s Reference Guide Chapter Line Backup Backup Configuration screen appears Atdt Backup Configuration screenIP Setup screen Connection Profiles Using Scheduled Connections with BackupScheduled Connections screen appears Management/Statistics Force Recovery Snmp Support QuickViewEvent Logs User’s Reference Guide Network Address Translation features Chapter IP Setup and Network Address TranslationHOW NAT Works Previous Screen Using Network Address TranslationV2 multicast Numbered Sdsl WAN1 Associating port numbers with nodesAdvanced IP/IPX router configuration options Data Link Options IP Setup and Network Address Translation Network Address Translation guidelines IP setup User’s Reference Guide Select Add Export. The Add Exported Service screen appears Select Service. a pop-up menu of services and ports appears IP subnets User’s Reference Guide Static routes Viewing static routes Static Routes screen will appearAdding a static route Deleting a static route Rules of static route installationModifying a static route Main Menu System Configuration IP Address Serving 176.163.222.10 Dhcp NetBios Options Serve Bootp Clients IP Address Pools IP Setup and Network Address Translation Dhcp NetBIOS Options NetBios Type MacIP KIP forwarding setup You have finished your IP setup User’s Reference Guide IPX features Chapter IPX SetupIPX definitions Internetwork Packet Exchange IPXIPX address Service Advertising Protocol SAPSocket Routing Information Protocol RIPIPX spoofing NetBIOSIPX setup screen Default Gateway Address IPX routing tables User’s Reference Guide AppleTalk protocol Chapter AppleTalk SetupAppleTalk networks AT Routing Table Routers and seeding MacIPInstalling AppleTalk Upgrade Feature Set Configuring AppleTalk EtherTalk setupLocalTalk setup Aurp Free Trade Zone Aurp setupViewing Aurp partners Modifying an Aurp partner Adding an Aurp partnerConfiguring Aurp Options Deleting an Aurp partnerReceiving Aurp connections Aurp Options Tickle Interval Hhmmss User’s Reference Guide Quick View status overview Chapter Monitoring ToolsGeneral status Status lights Current statusGeneral Statistics Statistics & LogsNetwork Interface Event historiesPhysical Interface WAN Event History Device Event History Routing tablesIP routing table AppleTalk routing table IPX routing tableIPX Sap Bindery table Served IP Addresses IP Address Lease Management screen appears Snmp System InformationCommunity strings Snmp Setup screenSnmp traps Viewing IP trap receivers Setting the IP trap receiversModifying IP trap receivers Deleting IP trap receiversWeb-based management pages Event History pages WAN Event History Device Event History User’s Reference Guide User accounts Chapter SecuritySuggested security measures Protecting the configuration screens Protecting the Security Options screenDial-in console access Telnet access Enable SmartStart/SmartView/Web serverAbout filters and filter sets What’s a filter and what’s a filter set?Filter priority How filter sets workHow individual filters work Port numbers filtering ruleParts of a filter Other filter attributes Port number comparisonsUDP Putting the parts togetherFiltering example #2 Filtering example #1Disadvantages of filters Design guidelinesWorking with IP filters and filter sets An approach to using filtersNaming a new filter set Adding a filter setAdding filters to a filter set Input and output filters-source and destinationADD this Filter NOW Cancel Viewing filters Viewing filter setsModifying filters Deleting filtersSample IP filter set Modifying filter setsDeleting a filter set TCP Icmp UDP Possible modifications User’s Reference Guide IPX filters Adding a packet filter IPX packet filtersViewing and modifying packet filters Deleting a packet filter IPX packet filter setsViewing and modifying packet filter sets Adding a packet filter setNo Match Viewing and modifying SAP filters IPX SAP filtersDeleting a packet filter set Deleting a SAP filter Adding a SAP filterAdding a SAP filter set IPX SAP filter setsViewing and modifying SAP filter sets Deleting a SAP filter set Basic protocol types Firewall tutorial General firewall termsBasic IP packet components Firewall Logic Firewall design rulesExample TCP/UDP Ports Logical and function Binary representationExample IP filter set screen Implied rulesEstablished connections Example network Filter basicsExample Example filtersExample Example Chapter Utilities and Diagnostics Ping Receive return Ping packet Stop Ping Trace RouteTelnet client Disconnect Telnet console session Factory defaultsUpdating firmware Transferring configuration and firmware files with TftpDownloading configuration files Transferring configuration and firmware files with Xmodem Uploading configuration filesIdle Do you want to send a saved configuration to your Netopia? Restarting the system Part III Appendixes User’s Reference Guide Configuration problems Appendix a TroubleshootingNetwork problems Console connection problemsPower outages How to reset the router to factory defaultsTechnical support How to reach usBefore contacting Netopia Environment profileFAX-Back Online product informationUser’s Reference Guide About IP addressing What is IP?Appendix B Understanding IP Addressing Subnets and subnet masks Subnet masks Example Using subnets on a Class C IP internetISP Network Network configurationBackground Example Working with a Class C subnetDistributing IP addresses Technical note on subnet masking Dhcp address serving Netopia R7200 Dhcp server characteristicsConfiguration Manually distributing IP addresses Using address servingMacIP serving Serve dynamic WAN clientsUnderstanding IP Addressing B-9 Tips and rules for distributing IP addressesDhcp example Internet Nested IP subnets0.0 C.1 WAN 3719 Packet header types BroadcastsUser’s Reference Guide Background Appendix C Understanding Netopia NAT BehaviorNetwork configuration User’s Reference Guide Understanding Netopia NAT Behavior C-3 Netopia Router WWW Server ISP Router LAN Understanding Netopia NAT Behavior C-5 Exported servicesImportant notes Understanding Netopia NAT Behavior C-7 Summary Appendix D Binary Conversion Table Decimal Binary Appendix E Further Reading User’s Reference Guide Further Reading E-3 User’s Reference Guide Pinouts for Auxiliary port modem cable Appendix F Technical Specifications and Safety InformationEnvironment Power requirementsDescription Software and protocols Regulatory notices Agency approvalsNorth America InternationalDeclaration for Canadian users Important safety instructionsBattery Telecommunication installation cautionsAppendix G About Sdsl User’s Reference Guide Glossary User’s Reference Guide Glossary User’s Reference Guide Remapping See network number remapping User’s Reference Guide Glossary User’s Reference Guide Numerics IndexIndex-2 Index-3 Index-4 Index-5 Index-6 Limited Warranty and Limitation of Remedies User’s Reference Guide
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