D-Link DWC-1000 User Manual page 194

Wireless Controller

NAT is a technique which allows several computers on a LAN to share an Internet
connection. The computers on the LAN use a "private" IP address range while
the Option port on the controller is configured with a single "public" IP address.
Along with connection sharing, NAT also hides internal IP addresses from the
computers on the Internet. NAT is required if your ISP has assigned only one IP
address to you. The computers that connect through the controller will need to
be assigned IP addresses from a private subnet.

Transparent routing between the LAN and Option does not perform NAT.
Broadcast and multicast packets that arrive on the LAN interface are switched to
the Option and vice versa, if they do not get filtered by firewall or VPN policies.
To maintain the LAN and Option in the same broadcast domain select
Transparent mode, which allows bridging of traffic from LAN to Option and vice
versa, except for controller -terminated traffic and other management traffic . All
DWC features are supported in transparen t mode assuming the LAN and Option
are configured to be in the same broadcast domain.

NAT routing has a feature called "NAT Hair -pinning" that allows internal
network users on the LAN and DMZ to access internal servers ( e.g. an
internal FTP server) using their externally-known domain name. This is also
referred to as "NAT loopback" since LAN generated traffic is redirected
through the firewall to reach LAN servers by their external name.
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User Manual