Draytek VigorNIC 132 series, User Manual

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VigorNIC 132 Series User’s Guide 65
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Local Area Network (LAN) is a group of subnets regulated and ruled by router. The design of
network structure is related to what type of public IP addresses coming from your ISP.
The most generic function of Vigor device is NAT. It creates a private subnet of your own. As
mentioned previously, the router will talk to other public hosts on the Internet by using public
IP address and talking to local hosts by using its private IP address. What NAT does is to
translate the packets from public IP address to private IP address to forward the right packets
to the right host and vice versa. Besides, Vigor device has a built-in DHCP server that assigns
private IP address to each local host. See the following diagram for a briefly understanding.
In some special case, you may have a public IP subnet from your ISP such as 220.135.240.0/24.
This means that you can set up a public subnet or call second subnet that each host is
equipped with a public IP address. As a part of the public subnet, the Vigor device will serve
for IP routing to help hosts in the public subnet to communicate with other public hosts or
servers outside. Therefore, the router should be set as the gateway for public hosts.