ATL Telecom AM30 - Manual (Page 71)

ATL Telecom User Guide
AM30
7
1
The RDR rule: Allowing external access to a LAN computer
You can create an RDR rule to make a computer on your LAN, such as a Web or FTP server,
available to Internet users without requiring you to obtain a public IP address for that
computer. The computer’s private IP address is translated to your public IP address in all
incoming and outgoing data packets.
Note
Without an RDR rule (or Bimap rule described on page 77),
the ROUTER blocks attempts by external computers to
access your LAN computers.
The following example illustrates using the RDR rule to provide external access to your web
server:
Your ADSL/Ethernet router receives a packet containing a
request for access to your Web server. The packet header
contains the public address for your LAN as the
destination IP address, and a destination port number of
80. Because you have set up an RDR rule for incoming
packets with destination port 80, the device recognizes
the data as a request for Web server access. The device
changes the packet's destination address to the private IP
address of your Web server and forwards the data packet
to it.
Your Web server sends data packets in response. Before
the ADSL/Ethernet router forwards them on to the
Internet, it changes the source IP address in the data
packets from the Web server's private address to your
LAN's public address. To an external Internet user then, it
appears as if your Web server uses your public IP address.
establish an RDR rule: Figure 35 shows the fields used to
Figure 35. NAT Rule – Add Page (RDR Flavor)