Subject:
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Re: ADSL and LAN (was: i neeeeeed help! can't logon to the lego site)
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Newsgroups:
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lugnet.robotics
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Date:
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Mon, 4 Jun 2001 23:20:32 GMT
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Original-From:
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Michel Gallant <mgallant@grassroots.ns.ca/StopSpammers/>
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Viewed:
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944 times
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On Fri, 1 Jun 2001, Mark Rideout wrote:
> 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.
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 router (if it can be made to work with
PPPoE; ADSL here doesn't use PPPoE where I live) is a good idea. I've
built a Linux router for my friend's home LAN. It's a 486 DX2-66, and
when it's routing (even 300K/sec of data) it has 98% processor free! The
routing code is built into the kernel in Linux; I imagine that it's a big,
clunky program in Win2k. In fact, because the linux kernel is still
running after you've run the shutdown command, you can shutdown the
machine (but leave it on, of course) for a completely unhackable router!
Michel
>
> 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
>
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