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Note : When using bandwidth management, configure the DSL LAN Extender device for the highest
line rate supported by the length and condition of the DSL cable.
Benefits of Using The DSL LAN Extender Device As An Internet Access
Gateway
You can configure a DSL LAN Extender CP with Bridging disabled and RIP either enabled or disabled.
In this mode, the DSL LAN Extender will act as an Internet access gateway, which treats the local LAN
side as one community. A good example of how this works is in a high-rise apartment building. You
could connect the residents on each floor to a DSL LAN Extender CP device. Each DSL LAN Extender
device, in turn, would connect to a DSL LAN Extender CO device.
Network Address Translation (NAT)
This option allows a group of computers connected to a DSL LAN Extender CP device to share a single
IP address, while still allowing the machines to use different private, internal IP addresses. This feature is
useful in situations where users are restricted by a limited (and usually small) number of public IP
addresses assigned by their Internet Service Provider (ISP). For example, by setting the Ethernet Side
Subnet Mask to 255.255.255.0, users have the flexibility of using 254 private, internal IP addresses for
their machines. Yet with NAT turned on, the outside world only sees one, public IP address (the DSL side
IP address) for all the machines.
The NAT option also enhances the security of your network because only a single IP address is presented
to the world, not every computer's IP address. This makes it harder for hackers to access the computers
on your network.
To turn on the NAT feature, select Y for the NAT Enabled option and enter the NAT IP address (such as
192.168.10.10) and its Subnet Mask (such as 255.255.255.0).
The CP routing configuration allows public IP addresses to co-exist with the sub-network that uses
private IP addresses. When the ISP has assigned more than one public IP address, you can use them for
the E-mail server and or the HTTP/FTP server. Please see Appendix C for more detailed examples.
Adding Support for Your E-Mail Server and HTTP/FTP Server
The DSL LAN Extender CP device supports the Simple Mail Transfer Protocol (SMTP) and Post Office
Protocol 3 (POP3). If you have an e-mail server on your local LAN to handle your organization's e-mail,
you can configure the DSL LAN Extender CP device to support this server. The advantages of setting up
your own e-mail server are as follows:
•
Reduce Internet traffic across the DSL connection. E-mail messages directed to PCs on the local LAN
aren't sent across to the remote side. Also, when people on the local LAN side check their e-mail,
their queries are sent to the local e-mail server, instead of over the DSL connection.
•
Provide flexibility in managing e-mail accounts. You can quickly and easily add, delete, or modify e-
mail accounts by yourself.
•
Provide greater security for internal e-mail.
To use an E-mail server, select Y for the E-Mail Server Enabled option. Enter the E-mail server's IP
address. If you have a HTTP/FTP server, you can also enter its IP address in the next field.
© 2002 Black Box Corporation
DSL LAN Extender 400 User's Guide
Page 14
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