How to configure your Alcatel
SpeedTouch ADSL modem to act as a transparent bridge?
This document describes how you can
configure an Alcatel SpeedTouch Pro ADSL modem not to use NAT
anymore, and not to perform the dialing to the ISP.
Note that you'll need a software
login method to achieve a connection to ADSL. Alternatively, there
are many relatively cheap and/or better Routers on the market which
perform these "port forwarding" requirements in a much easier and
reliable manner.
This process is often called
BRIDGING. The Alcatel modem will not receive the true IP address
from the ISP, instead it will be sent to your machine or Internet
Gateway box (or router). BRIDGING in the case of the Pro, is just a
fancy name for turning it into an ordinary ADSL modem and switching
off the Security and Internet Sharing features. This often becomes
necessary when trying to allow services like MSN Messenger, VPNs or
even running certain Servers.
The difference between BRIDGING and
DHCP SPOOFING (described here Configure Alcatel SpeedTouch ADSL for
DHCP Spoofing) is that with bridging the end-machine/router does the
dialing, and so it gets the real IP address from the ISP. With
spoofing the modem dials for you, receives the IP address from the
ISP, and then gives it to the end-machine/router.
As stated, this process will
therefore eliminating NAT on the Alcatel modem. It is also useful
for setups where combination of an Ethernet gateway routers which
have PPTP dialer support are in placed. Doing so will enable you to
configure an internal router or a server that has routing software
installed and have it receive an IP address from your ISP - instead
of having the modem obtain the address for you.
This method will work if one of the
following assumptions is true:
- Your modem is connected to the
Internet and another computer is connected to your modem.
- Your modem is connected to the
Internet and you have a router that is connected to the modem.
This router must have NAT capabilities and PPPoE dialing
capabilities. The router will then be connected to a hub/switch,
and to it other computers will connect.
- Your modem is connected to the
Internet and you have a server computer that is connected to the
modem. This server must have Routing and NAT capabilities and
will be configured to dial to the Internet. The server will then
be configured with another NIC, and to it you connect another
computer.
- Your modem is connected to the
Internet and you have a server computer that is connected to the
modem. This server must have Routing and NAT capabilities and
will be configured to dial to the Internet. The server will then
be configured with another NIC, to which you will then connect a
hub/switch, and to it other computers will connect.
Make a note of the fact that the
modem will stop acting as a router with NAT/PAT which means that
you'll have to connect it to a router or server that has NAT
capabilities. Without such configuration you won't be able to
connect to the Internet.
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