HOW NAT Works | Netopia R910 specification

9-52 User’s Reference Guide

Network Address Translation works by remapping the source IP address of trafﬁc from the LAN to a single static or dynamically assigned IP address shown to the remote side of the router.

HOW NAT WORKS

With NAT

ISP*

163.167.132.1

Without NAT

163.167.132.1 163.167.132.2 163.167.132.3 163.167.132.4 163.167.132.5 163.167.132.6

*or corporate intranet router

192.168.1.100

192.168.1.102

192.168.1.103

192.168.1.104

192.168.1.105

192.168.1.106

163.167.132.1 163.167.132.2 163.167.132.3

163.167.132.4 163.167.132.5 163.167.132.6

When NAT is enabled, the Netopia R910 can use either a statically assigned IP address or one dynamically assigned each time the router connects to the ISP. While a dynamically assigned IP address offers the ISP more ﬂexibility, it does have an important limitation: the router requires a static IP address to support Web, FTP, or other services available to the WAN. To support these services with NAT enabled, a service can be associated with only one machine on the LAN.

When connected to the Internet or some other large network using Network Address Translation, the individual machines on your LAN are not directly accessible from the WAN. NAT provides an inherently secure method of connection to the outside world.

Image 52

Netopia R910 manual HOW NAT Works

Contents

Netopia R910 Ethernet Router for DSL and Cable Modems Part Number Contents Iv User’s Reference Guide Contents Snmp Contents Index Chapter Introduction Features and capabilitiesOverview How to use this guide Chapter Setting Up Internet Services Deciding on an ISP accountDSL and cable modems Obtaining information from the ISP With Network Address Translation Local LAN IP address information to obtainWithout Network Address Translation Chapter Making the Physical Connections Find a location What you need Identify the connectors and attach the cablesLine 1 port Netopia R910 Ethernet Router back panel ports Your router on Netopia R910 Ethernet Router status lights 10 12 13 14 15 16 Network Model Chapter Connecting to Your Local Area NetworkBefore Readying computers on your local network After Connecting to Your Local Area Network Power port Console port Connecting to an Ethernet network10Base-T Netopia R910 in a 10Base-T network User’s Reference Guide Chapter Configuring TCP/IP Hardware and operating system requirements Conﬁguring TCP/IP on Windows 95 or Dynamic conﬁguration recommended Static conﬁguration optional Conﬁguring TCP/IP on a Macintosh Computer Static conﬁguration optional Dynamic conﬁguration using MacIP optional Conﬁguring TCP/IP User’s Reference Guide Chapter Console-Based Management Connecting through a Telnet session Snmp Simple Network Management Protocol. See Snmp on Connecting a console cable to your router Conﬁguring Telnet software Navigating through the console screens Mac ANSI, VT-100, or VT-200 Easy Setup console screens Chapter Easy SetupAccessing the Easy Setup console screens Screen similar to the following Main Menu appears If your ISP supports Dhcp Quick Easy Setup connection pathIf your ISP doesn’t support Dhcp Main Menu appears More Easy Setup options WAN Ethernet Conﬁguration IP Easy Setup Previous Screen Next Screen Easy Setup Security Conﬁguration User’s Reference Guide Chapter WAN and System Configuration WAN conﬁguration System conﬁguration screens Navigating through the system conﬁguration screens System conﬁguration features IP setup Filter sets ﬁrewallsIP address serving Date and time Upgrade feature set Console conﬁgurationSnmp Simple Network Management Protocol Security Logging Installing the Syslog client Chapter IP Setup and Network Address Translation Network Address Translation features HOW NAT Works Using Network Address Translation To Main Menu Associating port numbers with nodes Network Address Translation guideline IP Setup Ethernet IP Address IP Setup and Network Address Translation Select Add Export. The Add Exported Service screen appears Exports, Add Export, and Delete Export Select Service. a pop-up menu of services and ports appears IP subnets IP Setup and Network Address Translation Static routes Static Routes screen will appear Viewing static routes Adding a static route Modifying a static route Rules of static route installationDeleting a static route Main Menu System Configuration IP Address Serving Dhcp NetBios Options Serve Bootp Clients IP Address Pools IP Setup and Network Address Translation Dhcp NetBIOS Options NetBios Type User’s Reference Guide Chapter Virtual Private Networks VPN Transi t In t ern etwor k Summary Configuration Add Connection Profile Pptp configurationAbout Pptp Tunnels Chap User’s Reference Guide IP Proﬁle Parameters screen appears Encryption SupportMS-CHAP V2 and strong encryption Configuration About IPsec Tunnels Add Connection Proﬁle screen appears IPsec Encryption & Authentication Options IP Profile Parameters Advanced IP Profile Options Following section VPN Default Answer Profile VPN QuickView Interoperation with other featuresQuickView Virtual Private Networks VPN Installing Dial-Up Networking Dial-Up Networking for VPN Creating a new Dial-Up Networking profile Configuring a Dial-Up Networking profile Virtual Private Networks VPN Windows 95 VPN installation Installing the VPN ClientWindows 98 VPN installation Connecting using Dial-Up Networking Atmp configuration About Atmp Tunnels Pptp Commitcancel User’s Reference Guide Local WAN IP Address 0.0 Remote IP Address Allowing VPNs through a Firewall Pptp example on Atmp example on Pptp example Change Input Filter EnabledYes ForwardYes Source IP Address Change Output Filter EnabledYes ForwardYes Source IP Address Atmp example Source Port ID Dest. Port Compare Change Output Filter EnabledYes ForwardYes Source IP Address Setup EN WAN Module Chapter PPP over Ethernet Add Connection PPP Ethernet LAN Reconfiguration Quick View Chapter Monitoring Tools Quick View status overview General status Status lights Statistics & Logs General Statistics Physical Interface Event historiesNetwork Interface WAN Event History Device Event History Routing tables IP routing table Scroll Down Served IP Addresses System Information Snmp Setup screen Snmp Snmp traps Community strings Viewing IP trap receivers Setting the IP trap receiversModifying IP trap receivers Deleting IP trap receivers User’s Reference Guide Suggested security measures Chapter SecurityUser accounts Protecting the Security Options screen Protecting the conﬁguration screens Telnet access What’s a ﬁlter and what’s a ﬁlter set? About ﬁlters and ﬁlter setsHow ﬁlter sets work Filter priority ﬁlter’s actions How individual ﬁlters workﬁltering rule Parts of a ﬁlter Port numbers161 Aurp AppleTalk 387 Who 513 Other ﬁlter attributes Putting the parts together Internet Control Message Protocol Transmission Control ProtocolUser Datagram Protocol Filtering example #1 Design guidelines Filtering example #2 Working with IP ﬁlters and ﬁlter sets An approach to using ﬁltersDisadvantages of ﬁlters Adding a ﬁlter set Naming a new ﬁlter set Netopia R910 Router Input and output ﬁlters-source and destinationAdding ﬁlters to a ﬁlter set ADD this Filter NOW Cancel Viewing ﬁlter sets Viewing ﬁltersModifying ﬁlters Deleting ﬁlters Deleting a ﬁlter set Modifying ﬁlter setsSample IP ﬁlter set TCP Icmp UDP Possible modiﬁcations User’s Reference Guide Firewall tutorial General ﬁrewall terms Basic IP packet componentsBasic protocol types ACK Bit Yes Example TCP/UDP Ports Firewall design rulesFirewall Logic Logical and function Binary representationImplied rules Filter basics Established connectionsExample IP ﬁlter set screen This is an example of the Netopia IP ﬁlter set screen Example network Example ﬁltersExample Example Example User’s Reference Guide Radius client configuration Radius Client Support Radius Server Secret Continue Cancel Continue Chapter Utilities and Diagnostics Ping Start Ping Receive return Ping packet Trace Route Stop Ping Telnet client Disconnect Telnet console session Factory defaultsTransferring conﬁguration and ﬁrmware ﬁles with Tftp Updating ﬁrmware Downloading conﬁguration ﬁles Press Return. You will see the following dialog box Uploading conﬁguration ﬁles Transferring conﬁguration and ﬁrmware ﬁles with Xmodem Idle Do you want to send a saved configuration to your Netopia? Restarting the system Appendix a Troubleshooting Conﬁguration problems Console connection problems Network problems How to reset the router to factory defaults Power outages How to reach us Technical supportBefore contacting Netopia Environment proﬁle Product information can be found in the following Online product informationOnline Technical Support User’s Reference Guide Appendix B Understanding IP Addressing What is IP?About IP addressing Subnets and subnet masks Example Using subnets on a Class C IP internet Subnet masks Network conﬁguration ISP Network Distributing IP addresses Example Working with a Class C subnetBackground Technical note on subnet masking 255.255.255.224 Netopia R910 Dhcp server characteristics Conﬁguration255.255.255.0 Dhcp address serving Using address serving Manually distributing IP addressesTips and rules for distributing IP addresses MacIP serving Understanding IP Addressing B-181 Nested IP subnets Dhcp example Internet 0.0 C.1 WAN 3719 Broadcasts Packet header types User’s Reference Guide Network conﬁguration Appendix C Understanding Netopia NAT BehaviorBackground User’s Reference Guide Understanding Netopia NAT Behavior C-189 Router Netopia Exported services Understanding Netopia NAT Behavior C-191 Important notes Understanding Netopia NAT Behavior C-193 Summary Appendix D Binary Conversion Table Decimal Binary Appendix E Further Reading User’s Reference Guide Further Reading E-199 User’s Reference Guide Appendix F Technical Specifications and Safety Information Regulatory notices Declaration for Canadian users Telecommunication installation cautions Important safety instructionsBattery User’s Reference Guide Index Deﬁned B-180 Index-206 Index-207 Index-208 SmartIP Index-209