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eir F1000 Modem User
’s Guide
Chapter 9 Network Address Translation (NAT)
9.9.3 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
Device keeps track of the original addresses and port numbers so incoming reply packets can have
their original values restored. The following figure illustrates this.
Figure 94
How NAT Works
NAT Table
LAN
192.168.1.13
192.168.1.12
SA
192.168.1.10
Inside Local
IP Address
192.168.1.10
192.168.1.11
192.168.1.12
192.168.1.13
Inside Global
IP Address
IGA 1
IGA 2
IGA 3
IGA 4
SA
IGA1
WAN
192.168.1.11
192.168.1.10
Inside Local
Address (ILA)
Inside Global
Address (IGA)
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Страница 180: ...Chapter 11 Interface Group 180 eir F1000 Modem User s Guide...
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Страница 200: ...200 eir F1000 Modem User s Guide Chapter 15 Parental Control...
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Страница 228: ...Chapter 19 Log 228 eir F1000 Modem User s Guide...
Страница 248: ...248 eir F1000 Modem User s Guide Chapter 27 User Account...
Страница 252: ...Chapter 28 Remote Management 252 eir F1000 Modem User s Guide...
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Страница 260: ...Chapter 31 Time Settings 260 eir F1000 Modem User s Guide...
Страница 266: ...Chapter 33 Log Setting 266 eir F1000 Modem User s Guide...
Страница 272: ...Chapter 35 Configuration 272 eir F1000 Modem User s Guide...
Страница 278: ...Chapter 36 Diagnostic 278 eir F1000 Modem User s Guide...
Страница 324: ...324 eir F1000 Modem User s Guide Appendix C Pop up Windows JavaScripts and Java Permissions...
Страница 338: ...338 eir F1000 Modem User s Guide Appendix D Wireless LANs...