[plug] Install tonight

[Andrew Pamment]

On Tue, 25 Feb 2003 00:55:01 +0800 (WST), Mike Holland 
<myk at plug.linux.org.au> wrote:


>> Mike [Gilks] is building a firewall to sit between the ADSL modem (which
>> has an ethernet interface) and his internal LAN which means the second
>> NIC on the firewall is going to a switch/hub connected to all his other
>> computers.
>
> I understand that, but cannot see why you need two physically separated 
> ethernets. Why cant the PPPoE packets travel over the same ethernet as 
> the IP packets? Ethernet allows multiple protocols to share the physical 
> layer, while remaining conceptually separate.
> Perhaps it is a limitation that the Linux PPPoE cannot share a NIC?

I am no way qualified to answer this question, but I am going to give it a 
shot. Ethernet is a broadcast thingo. the packets (whatever protocol) whizz 
through to all the things plugged into the ethernet i think.

thats why you can watch pakets zooming on your LAN even if you are not the 
sender or the recipiant.

If you used you LAN ethernet with your ADSL modem, all your local ethernet 
packets would whizz through the adsl modem. This is not desired.

I think when you create a PPPoE connection it makes a ppp sort of tunnel on 
this broadcast medium. those packets whizz though the ethernet, just as any 
other packet would be it using IPX/SPX, TCP/IP or Appletalk. they all do a 
lot of whizzing.

Does that make sense? It wouldn't be safe to have your local packets 
zooming off to the internet, and it would probably annoy your ISP.

Am I totally wrong? I wish to learn too.
Andrew

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