Chapter 10 Network Address Translation (NAT)
10.6.3 How NAT Works
Each packet has two addresses – a source address and a destination address. For outgoing packets, the inside local address is the source address on the LAN, and the inside public address is the source address on the WAN. For incoming packets, the inside local address is the destination address on the LAN, and the inside public address 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
Figure 39 How NAT Works
NAT Table
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192.168.1.13 | 192.168.1.10 |
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192.168.1.11 |
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| 192.168.1.12 |
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| 192.168.1.13 |
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192.168.1.12 |
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| SA |
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| 192.168.1.10 |
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WAN
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Inside Local | Inside | Public | |
Address | Address |
192.168.1.11 192.168.1.10
| 99 |
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