Prestige 662HW Series User’s Guide
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Chapter 10 Network Address Translation (NAT) Screens
10.1.2 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)
.
10.1.3 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.
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Страница 7: ...Prestige 662HW Series User s Guide 7 Customer Support...
Страница 43: ...Prestige 662HW Series User s Guide 43 Introduction to DSL...
Страница 53: ...Prestige 662HW Series User s Guide 53 Chapter 1 Getting To Know Your Prestige...
Страница 59: ...Prestige 662HW Series User s Guide 59 Chapter 2 Introducing the Web Configurator...
Страница 77: ...Prestige 662HW Series User s Guide 77 Chapter 5 Password Setup...
Страница 89: ...Prestige 662HW Series User s Guide 89 Chapter 7 DMZ...
Страница 111: ...Prestige 662HW Series User s Guide 111 Chapter 8 Wireless LAN Setup...
Страница 127: ...Prestige 662HW Series User s Guide 127 Chapter 9 WAN Setup...
Страница 139: ...Prestige 662HW Series User s Guide 139 Chapter 10 Network Address Translation NAT Screens...
Страница 157: ...Prestige 662HW Series User s Guide 157 Chapter 13 Firewalls...
Страница 203: ...Prestige 662HW Series User s Guide 203 Chapter 16 Content Access Control...
Страница 211: ...Prestige 662HW Series User s Guide 211 Chapter 17 Anti Virus Packet Scan...
Страница 217: ...Prestige 662HW Series User s Guide 217 Chapter 18 Introduction to IPSec...
Страница 249: ...Prestige 662HW Series User s Guide 249 Chapter 20 Remote Management Configuration...
Страница 263: ...Prestige 662HW Series User s Guide 263 Chapter 21 Universal Plug and Play UPnP...
Страница 269: ...Prestige 662HW Series User s Guide 269 Chapter 22 Logs Screens...
Страница 295: ...Prestige 662HW Series User s Guide 295 Chapter 24 Maintenance...
Страница 301: ...Prestige 662HW Series User s Guide 301 Chapter 25 Introducing the SMT...
Страница 305: ...Prestige 662HW Series User s Guide 305 Chapter 26 Menu 1 General Setup...
Страница 319: ...Prestige 662HW Series User s Guide 319 Chapter 29 Wireless LAN Setup...
Страница 325: ...Prestige 662HW Series User s Guide 325 Chapter 30 Internet Access...
Страница 339: ...Prestige 662HW Series User s Guide 339 Chapter 32 Static Route Setup...
Страница 343: ...Prestige 662HW Series User s Guide 343 Chapter 33 Bridging Setup...
Страница 375: ...Prestige 662HW Series User s Guide 375 Chapter 36 Filter Configuration...
Страница 395: ...Prestige 662HW Series User s Guide 395 Chapter 39 System Information and Diagnosis...
Страница 411: ...Prestige 662HW Series User s Guide 411 Chapter 40 Firmware and Configuration File Maintenance...
Страница 417: ...Prestige 662HW Series User s Guide 417 Chapter 41 System Maintenance...
Страница 421: ...Prestige 662HW Series User s Guide 421 Chapter 42 Remote Management...
Страница 433: ...Prestige 662HW Series User s Guide 433 Chapter 44 Call Scheduling...
Страница 449: ...Prestige 662HW Series User s Guide 449 Chapter 46 SA Monitor...
Страница 453: ...Prestige 662HW Series User s Guide 453 Chapter 47 Internal SPTGEN...
Страница 459: ...Prestige 662HW Series User s Guide 459 Appendix A Pin Assignments Figure 290 Ethernet Cable Pin Assignments...
Страница 479: ...Prestige 662HW Series User s Guide 479 Appendix C IP Subnetting...
Страница 485: ...Prestige 662HW Series User s Guide 485 Appendix E Wireless LAN and IEEE 802 11...
Страница 492: ...Prestige 662HW Series User s Guide Appendix H Triangle Route 492...
Страница 493: ...Prestige 662HW Series User s Guide 493 Appendix H Triangle Route...
Страница 525: ...Prestige 662HW Series User s Guide 525 Appendix K Example Internal SPTGEN Screens...
Страница 527: ...Prestige 662HW Series User s Guide 527 Appendix L Command Interpreter...
Страница 529: ...Prestige 662HW Series User s Guide 529 Appendix M Firewall Commands...
Страница 533: ...Prestige 662HW Series User s Guide 533 Appendix N NetBIOS Filter Commands...
Страница 535: ...Prestige 662HW Series User s Guide 535 Appendix O Brute Force Password Guessing Protection...