ZyXEL Communications ZyWall USG20-VPN, Руководство пользователя

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Chapter 21 IPSec VPN
USG20(W)-VPN Series User’s Guide
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• Destination - the original destination address; the local network ( A ).
• SNAT - the translated source address; a different IP address (range of addresses) to hide the
original source address.
Destination Address in Inbound Packets (Inbound Traffic, Destination NAT)
You can set up this translation if you want the USG to forward some packets from the remote
network to a specific computer in the local network. For example, in
Figure 238 on page 366 , you
can configure this kind of translation if you want to forward mail from the remote network to the
mail server in the local network (
A ).
You have to specify one or more rules when you set up this kind of NAT. The USG checks these rules
similar to the way it checks rules for a security policy. The first part of these rules define the
conditions in which the rule apply.
• Original IP - the original destination address; the remote network ( B ).
• Protocol - the protocol [TCP, UDP, or both] used by the service requesting the connection.
• Original Port - the original destination port or range of destination ports; in
Figure 238 on page
366 , it might be port 25 for SMTP.
The second part of these rules controls the translation when the condition is satisfied.
• Mapped IP - the translated destination address; in Figure 238 on page 366 , the IP address of the
mail server in the local network ( A ).
• Mapped Port - the translated destination port or range of destination ports.
The original port range and the mapped port range must be the same size.
IPSec VPN Example Scenario
Here is an example site-to-site IPSec VPN scenario.
Figure 239
Site-to-site IPSec VPN Example
192.168.1.0/24
172.16.1.0/24
1.2.3.4
2.2.2.2
LAN
LAN