Chapter 11 Network Address Translation (NAT)
VMG1312-B10A User’s Guide
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11.8.3 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 83
How NAT Works
192.168.1.13
192.168.1.10
192.168.1.11
192.168.1.12
SA
192.168.1.10
SA
IGA1
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
NAT Table
WAN
LAN
Inside Local
Address (ILA)
Inside Global
Address (IGA)
Summary of Contents for VWG1312-B10A
Page 2: ......
Page 8: ...Contents Overview VMG1312 B10A User s Guide 8 Troubleshooting 291 ...
Page 18: ...Table of Contents VMG1312 B10A User s Guide 18 ...
Page 19: ...19 PART I User s Guide ...
Page 20: ...20 ...
Page 34: ...Chapter 2 The Web Configurator VMG1312 B10A User s Guide 34 ...
Page 39: ...Chapter 4 Tutorials VMG1312 B10A User s Guide 39 7 Click Apply to save your settings ...
Page 79: ...79 PART II Technical Reference ...
Page 80: ...80 ...
Page 168: ...Chapter 9 Routing VMG1312 B10A User s Guide 168 ...
Page 186: ...Chapter 10 Quality of Service QoS VMG1312 B10A User s Guide 186 ...
Page 212: ...Chapter 13 Interface Group VMG1312 B10A User s Guide 212 ...
Page 228: ...Chapter 15 Firewall VMG1312 B10A User s Guide 228 ...
Page 234: ...Chapter 17 Parental Control VMG1312 B10A User s Guide 234 ...
Page 244: ...Chapter 19 Certificates VMG1312 B10A User s Guide 244 ...
Page 248: ...Chapter 20 Log VMG1312 B10A User s Guide 248 ...
Page 252: ...Chapter 21 Traffic Status VMG1312 B10A User s Guide 252 ...
Page 258: ...Chapter 24 IGMP Status VMG1312 B10A User s Guide 258 ...
Page 262: ...Chapter 25 xDSL Statistics VMG1312 B10A User s Guide 262 ...
Page 264: ...Chapter 26 User Account VMG1312 B10A User s Guide 264 ...
Page 270: ...Chapter 29 TR 064 VMG1312 B10A User s Guide 270 ...
Page 274: ...Chapter 30 Time Settings VMG1312 B10A User s Guide 274 ...
Page 280: ...Chapter 32 Logs Setting VMG1312 B10A User s Guide 280 ...
Page 298: ...Chapter 36 Troubleshooting VMG1312 B10A User s Guide 298 ...
Page 338: ...Appendix C Pop up Windows JavaScripts and Java Permissions VMG1312 B10A User s Guide 338 ...
Page 352: ...Appendix D Wireless LANs VMG1312 B10A User s Guide 352 ...
Page 368: ...Appendix G Legal Information VMG1312 B10A User s Guide 368 ...
Page 376: ...VMG1312 B10A User s Guide 376 Index ...