Re: ADSL connection qustion

From: Leon. (noemail_at_noemail.noemail.com)
Date: 12/17/03 

Date: Wed, 17 Dec 2003 20:48:14 +1100

"Justin" <yu0123@justin7.freeserve.co.uk> wrote in message
news:brof0p$br5$1@

>However, it does not mean staic IP addresses.

thats correct.

> Usually, ISP's will provide DHCP services from the C.O., or
> from a DHCP server running on the DSL modem.

Thats very misleading and confused compared to reality. Forget it.
He didnt say this sentence.

DHCP at the client side is up to the client, the ISP has no say.
How the ISP allocates IP addresses is up to it, dont worry about it.

Modems dont do anything like this, routers do. But theres the silly hybrid
things which are between modems and routers, just treat them like a modem
and forget how they actually do it, it wont help you to think about this
hybrids.

> I think i had the wrong idea about ADSL connections, from what you said,
an
> ADSL connection is unlike a dial up connection, once I power up my ADSL
> modem the connection is made.

No its just like a modem call. The modems at each end negotiate to talk to
each other, then there is a authentication phase and then they exchange Ip
addresses ... just like PPP over phone modems.

> modem to do that obviously, so how I can get the linux router to do that
for
> the whole LAN automatically everytime authentication is required? (you
> mentioned pppoe, will that do this job?)

yes, the PPPoE client uses the modem , as ppp uses a v90 phone modem.
The Internet IP address appears on an interface on the linux box. The linux
box then can contact the internet, and you can then set up the firewall as
nat/masquerade, and/or set up proxy servers.

>and is it possible to use any of
> the LAN computers to authenticate through the router?

PPPoE talks to the modem via ETHERNET addresses, so there is no simple way
for this to occur.

Linux doesnt route Ethernet, it routes tcp/ip.

You could set up the linux box for bridging and then it would allow PPPoE to
work between a PC on the LAN and the modem. but then the ISP also needs to
allow this, you need a seperate login, and most ISPs dont want to give you
multiple login accounts.

Routers/Firewall hardware run PPP, they can be configured to stay connected,
or connect on demand. but basically the ISP is happy for you to stay logged
in , it doesnt consume any resources!

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