Prestige 661H/HW Series User’s Guide
115
Chapter 8 Network Address Translation (NAT) Screens
8.1.2 What NAT Does
In the simplest form, NAT changes the source IP address in a packet received from a
subscriber (the inside local address) to another (the inside global address) before forwarding
the packet to the WAN side. When the response comes back, NAT translates the destination
address (the inside global address) back to the inside local address before forwarding it to the
original inside host. Note that the IP address (either local or global) of an outside host is never
changed.
The global IP addresses for the inside hosts can be either static or dynamically assigned by the
ISP. In addition, you can designate servers, for example, a web server and a telnet server, on
your local network and make them accessible to the outside world. If you do not define any
servers (for Many-to-One and Many-to-Many Overload mapping – see
NAT offers the additional benefit of firewall protection. With no servers defined, your
Prestige filters out all incoming inquiries, thus preventing intruders from probing your
network. For more information on IP address translation, refer to
RFC 1631
,
The IP Network
Address Translator (NAT)
.
8.1.3 How NAT Works
Each packet has two addresses – a source address and a destination address. For outgoing
packets, the ILA (Inside Local Address) is the source address on the LAN, and the IGA (Inside
Global Address) is the source address on the WAN. For incoming packets, the ILA is the
destination address on the LAN, and the IGA is the destination address on the WAN. NAT
maps private (local) IP addresses to globally unique ones required for communication with
hosts on other networks. It replaces the original IP source address (and TCP or UDP source
port numbers for Many-to-One and Many-to-Many Overload NAT mapping) in each packet
and then forwards it to the Internet. The Prestige keeps track of the original addresses and port
numbers so incoming reply packets can have their original values restored. The following
figure illustrates this.
Содержание Prestige 661H Series
Страница 37: ...Prestige 661H HW Series User s Guide 37 List of Tables...
Страница 41: ...Prestige 661H HW Series User s Guide 41 Introduction to DSL...
Страница 51: ...Prestige 661H HW Series User s Guide 51 Chapter 1 Getting To Know Your Prestige...
Страница 67: ...Prestige 661H HW Series User s Guide 67 Chapter 3 Wizard Setup for Internet Access...
Страница 81: ...Prestige 661H HW Series User s Guide 81 Chapter 5 LAN Setup...
Страница 125: ...Prestige 661H HW Series User s Guide 125 Chapter 8 Network Address Translation NAT Screens...
Страница 143: ...Prestige 661H HW Series User s Guide 143 Chapter 11 Firewalls...
Страница 151: ...Prestige 661H HW Series User s Guide 151 Chapter 12 Firewall Configuration Figure 64 Firewall Edit Rule...
Страница 165: ...Prestige 661H HW Series User s Guide 165 Chapter 12 Firewall Configuration...
Страница 169: ...Prestige 661H HW Series User s Guide 169 Chapter 13 Content Filtering...
Страница 175: ...Prestige 661H HW Series User s Guide 175 Chapter 14 Introduction to IPSec...
Страница 203: ...Prestige 661H HW Series User s Guide 203 Chapter 15 VPN Screens...
Страница 207: ...Prestige 661H HW Series User s Guide 207 Chapter 16 Remote Management Configuration...
Страница 221: ...Prestige 661H HW Series User s Guide 221 Chapter 17 Universal Plug and Play UPnP...
Страница 227: ...Prestige 661H HW Series User s Guide 227 Chapter 18 Logs Screens...
Страница 241: ...Prestige 661H HW Series User s Guide 241 Chapter 19 Media Bandwidth Management Advanced Setup...
Страница 265: ...Prestige 661H HW Series User s Guide 265 Chapter 21 Maintenance...
Страница 275: ...Prestige 661H HW Series User s Guide 275 Chapter 23 Menu 1 General Setup...
Страница 279: ...Prestige 661H HW Series User s Guide 279 Chapter 24 Menu 2 WAN Backup Setup...
Страница 283: ...Prestige 661H HW Series User s Guide 283 Chapter 25 Menu 3 LAN Setup...
Страница 287: ...Prestige 661H HW Series User s Guide 287 Chapter 26 Wireless LAN Setup...
Страница 293: ...Prestige 661H HW Series User s Guide 293 Chapter 27 Internet Access...
Страница 307: ...Prestige 661H HW Series User s Guide 307 Chapter 29 Static Route Setup...
Страница 311: ...Prestige 661H HW Series User s Guide 311 Chapter 30 Bridging Setup...
Страница 327: ...Prestige 661H HW Series User s Guide 327 Chapter 31 Network Address Translation NAT...
Страница 343: ...Prestige 661H HW Series User s Guide 343 Chapter 33 Filter Configuration...
Страница 363: ...Prestige 661H HW Series User s Guide 363 Chapter 36 System Information and Diagnosis...
Страница 375: ...Prestige 661H HW Series User s Guide 375 Chapter 37 Firmware and Configuration File Maintenance...
Страница 381: ...Prestige 661H HW Series User s Guide 381 Chapter 38 System Maintenance...
Страница 385: ...Prestige 661H HW Series User s Guide 385 Chapter 39 Remote Management...
Страница 395: ...Prestige 661H HW Series User s Guide 395 Chapter 40 IP Policy Routing...
Страница 399: ...Prestige 661H HW Series User s Guide 399 Chapter 41 Call Scheduling...
Страница 411: ...Prestige 661H HW Series User s Guide 411 Chapter 42 VPN IPSec Setup...
Страница 415: ...Prestige 661H HW Series User s Guide 415 Chapter 43 SA Monitor...
Страница 427: ...Prestige 661H HW Series User s Guide 427 Chapter 44 Troubleshooting Figure 275 Security Setting ActiveX Controls...
Страница 431: ...Prestige 661H HW Series User s Guide 431 Appendix A...
Страница 451: ...Prestige 661H HW Series User s Guide 451 Appendix C IP Subnetting...
Страница 455: ...Prestige 661H HW Series User s Guide 455 Appendix E Command Interpreter...
Страница 461: ...Prestige 661H HW Series User s Guide 461 Appendix F Firewall Commands...
Страница 464: ...Prestige 661H HW Series User s Guide Appendix G NetBIOS Filter Commands 464...
Страница 465: ...Prestige 661H HW Series User s Guide 465 Appendix G NetBIOS Filter Commands...
Страница 478: ...Prestige 661H HW Series User s Guide Appendix H VPN Setup 478 ftp 5631148 bytes sent in 614 8Seconds 9 17Kbytes sec...
Страница 479: ...Prestige 661H HW Series User s Guide 479 Appendix H VPN Setup...
Страница 482: ...Prestige 661H HW Series User s Guide Appendix I Splitters and Microfilters 482...
Страница 483: ...Prestige 661H HW Series User s Guide 483 Appendix I Splitters and Microfilters...
Страница 537: ...Prestige 661H HW Series User s Guide 537 Appendix M Internal SPTGEN...