ZyXEL Communications Corporation EMG6765-Q10A Manuel D’Utilisation
Chapter 13 NAT
EMG6765-Q10A User’s Guide
111
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 in each packet and then forwards it to the Internet. The EMG6765-Q10A keeps track of the
original addresses and port numbers so incoming reply packets can have their original values restored.
The following figure illustrates this.
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 in each packet and then forwards it to the Internet. The EMG6765-Q10A 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 59 How NAT Works
13.2 General
Use this screen to enable NAT and set a default server. Click Network > NAT to open the General screen.
Figure 60 Network > NAT > General