Prestige 2602HW Series User’s Guide
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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
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.
Summary of Contents for Prestige 2602HW Series
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Page 40: ...Prestige 2602HW Series User s Guide 40 Introduction to DSL...
Page 72: ...Prestige 2602HW Series User s Guide 72 Chapter 4 Password Setup...
Page 102: ...Prestige 2602HW Series User s Guide 102 Chapter 6 Wireless LAN Setup...
Page 112: ...Prestige 2602HW Series User s Guide 112 Chapter 7 WAN Setup...
Page 124: ...Prestige 2602HW Series User s Guide 124 Chapter 8 Network Address Translation NAT Screens...
Page 130: ...Prestige 2602HW Series User s Guide 130 Chapter 9 Introduction to VoIP...
Page 142: ...Prestige 2602HW Series User s Guide 142 Chapter 10 Voice Screens...
Page 148: ...Prestige 2602HW Series User s Guide 148 Chapter 12 Time and Date...
Page 162: ...Prestige 2602HW Series User s Guide 162 Chapter 13 Firewalls...
Page 192: ...Prestige 2602HW Series User s Guide 192 Chapter 16 Remote Management Configuration...
Page 206: ...Prestige 2602HW Series User s Guide 206 Chapter 17 Universal Plug and Play UPnP...
Page 212: ...Prestige 2602HW Series User s Guide 212 Chapter 18 Logs Screens...
Page 214: ...Prestige 2602HW Series User s Guide 214 Chapter 19 Maintenance Figure 102 System Status...
Page 224: ...Prestige 2602HW Series User s Guide 224 Chapter 19 Maintenance...
Page 232: ...Prestige 2602HW Series User s Guide 232 Chapter 20 Introducing the SMT...
Page 236: ...Prestige 2602HW Series User s Guide 236 Chapter 21 Menu 1 General Setup...
Page 240: ...Prestige 2602HW Series User s Guide 240 Chapter 22 Menu 2 WAN Backup Setup...
Page 244: ...Prestige 2602HW Series User s Guide 244 Chapter 23 Menu 3 LAN Setup...
Page 248: ...Prestige 2602HW Series User s Guide 248 Chapter 24 Wireless LAN Setup...
Page 254: ...Prestige 2602HW Series User s Guide 254 Chapter 25 Internet Access...
Page 268: ...Prestige 2602HW Series User s Guide 268 Chapter 27 Static Route Setup...
Page 272: ...Prestige 2602HW Series User s Guide 272 Chapter 28 Bridging Setup...
Page 288: ...Prestige 2602HW Series User s Guide 288 Chapter 29 Network Address Translation NAT...
Page 304: ...Prestige 2602HW Series User s Guide 304 Chapter 31 Filter Configuration...
Page 324: ...Prestige 2602HW Series User s Guide 324 Chapter 34 System Information and Diagnosis...
Page 340: ...Prestige 2602HW Series User s Guide 340 Chapter 35 Firmware and Configuration File Maintenance...
Page 346: ...Prestige 2602HW Series User s Guide 346 Chapter 36 System Maintenance...
Page 350: ...Prestige 2602HW Series User s Guide 350 Chapter 37 Remote Management...
Page 362: ...Prestige 2602HW Series User s Guide 362 Chapter 39 Call Scheduling...
Page 366: ...Prestige 2602HW Series User s Guide 366 Chapter 40 Internal SPTGEN...
Page 372: ...Prestige 2602HW Series User s Guide 372 Chapter 41 Troubleshooting...
Page 376: ...Prestige 2602HW Series User s Guide 376 Appendix A Hardware Specifications...
Page 396: ...Prestige 2602HW Series User s Guide 396 Appendix C IP Subnetting...
Page 402: ...Prestige 2602HW Series User s Guide 402 Appendix E Wireless LAN and IEEE 802 11...
Page 409: ...Prestige 2602HW Series User s Guide Appendix H Triangle Route 409...
Page 410: ...Prestige 2602HW Series User s Guide 410 Appendix H Triangle Route...
Page 434: ...Prestige 2602HW Series User s Guide 434 Appendix J Command Interpreter...
Page 436: ...Prestige 2602HW Series User s Guide 436 Appendix K Firewall Commands...