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Subject: 
ADSL and LAN (was: i neeeeeed help! can't logon to the lego site)
Newsgroups: 
lugnet.robotics, lugnet.off-topic.geek
Followup-To: 
lugnet.off-topic.geek
Date: 
Fri, 1 Jun 2001 18:47:10 GMT
Viewed: 
871 times
  
In lugnet.robotics, "Simon Bogaert" <Simon.Bogaert@advalvas.be> writes:
Hi,

I guess you are subscribed to an ADSL service and I also guess you have an
external ADSL modem.

If these guesses are correct, here's the explanation for the IP address
stuff.  The ADSL modem uses your ethernet card as an interface to talk to
your computer.  The ADSL modem also uses the PPPoE
(poin-to-point-over-ethernet) protocol to obtain an IP address automatically
from your provider.  The interface that your internet programs connect to,
to send information to the internet, is a software-program that takes care
of the traffic between the Ethernet card and the ADSL-modem (I think it
makes the ethernet-interface send out information in a format the ADSL modem
understands) This IP address is refreshed every time you logon or every x
hours when you leave your computer on all the time.  This PPPoE method for
obtainig an IP address is different from the default DHCP method.

And this is where the IP address configuration in MS network properties
kicks in.  If you specify "obtain an IP-address automatically", Windows
sends out a DHCP-discovery package (a package that's sent out to a listening
DHCP server that gives you an IP address out of an array when it "hears" a
DHCP-discovery package) when it tries to logon to your network (which can't
be present, the ADSL modem occupies your Ethernet card physically).  Off
course (due to the non-standard PPPoE way of obtaining an IP-address) this
package is never answered, and the network interface (software!) stays
addressless.  I don't know if Windows networking repeats the DHCP-discovery
package or not, but that doesn't matter here and now.

So every time the ADSL software-networkinterface (the program that looks a
bit like Dial-up-networking) sends out a package that, let's say, your
browser initiated, it sends it out through the ethernet interface.  Windows
networking "sees" that a package is sent out through the addressless
interface, and gets confused.  What it does exactly then, I don't know, but
normally, the ADSL software just carries on doing what it should do, without
ever minding the Windows networking being confused.  This way, these two
programs may interfere (the confused windows networkinterface messes up the
ADSL packages because it has no IP-address) and the browser may output a
website-not-found error due to the FUBAR'ed network traffic.

To avoid Windows outputting the DHCP-discovery package, you have to switch
off this option in MS networking properties, and specify a so-called private
IP-address.  That's an address out of an array of IP-addresses that are not
allowed on the internet.  This way, the two interfaces will never interfere
with eachother's traffic.  This also means, that if you first shut down the
ADSL software interface and disconnect the ADSL modem physically, you can
just pop in the connector for an internal network and start using it right
away.

So what it all boils down to, is that two software interfaces to the same
hardware interface get in eachother's way.  I hope my explanation is clear
enough and hasn't confused you all too much.  As I'm not a professional,
please someone correct me if I'm wrong.

Simon


So here is my question with ADSL - can it be used, and work well with, a
private LAN? I have a LAN (Win2k server based) in my house that includes the
server being a DNS server, DHCP server and Domain controller. I have this
configuration so that I can have a domain for development/programming
reasons. I basically want to have all computers on the LAN be able to access
the internet. I've been really interested in ADSL/DSL (does it matter?) but
haven't been able to find a good answer to this question if this
configuration can work. I would think I could put the DSL modem/net card in
the server and also have the LAN network card (basically dual-homed server)
and have the server act as a "software" based router/firewall.

I'm kinda new to networking, though I was able to setup my home LAN, so
please define any acronyms that might be used.

thanks
Mark



Message has 2 Replies:
  Re: ADSL and LAN (was: i neeeeeed help! can't logon to the lego site)
 
(...) Get one of the LinkSYS Cable/DSL Routers (~$200 CDN$ for a 4 port), or learn to use linux and setup a firewall machine. (23 years ago, 1-Jun-01, to lugnet.robotics)
  Re: ADSL and LAN (was: i neeeeeed help! can't logon to the lego site)
 
(...) This will work. However, people have complained that the routing makes the Win2k machine thrash like crazy. As long as the machine isn't doing much else, you should be fine. If it needs to do other things, using a Linux machine as a dedicated (...) (23 years ago, 4-Jun-01, to lugnet.robotics)

Message is in Reply To:
  Re: i neeeeeed help! can't logon to the lego site
 
Hi, I guess you are subscribed to an ADSL service and I also guess you have an external ADSL modem. If these guesses are correct, here's the explanation for the IP address stuff. The ADSL modem uses your ethernet card as an interface to talk to your (...) (23 years ago, 1-Jun-01, to lugnet.robotics)

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