[Gllug] ADSL modem -- WTF?

[Doug Winter]

On Thu 15 Jul Chris Bell wrote:
>    I understand that if your firewall is configured to run PPPoE and the
> ADSL modem is just used to convert between PPPoE and PPPoA, then the ADSL
> modem can have a non-routable IP address, and the connecting ethernet
> interface on your firewall can carry the assigned IP address. The system
> should just work as well as if there was any other hardware, including an
> analogue modem, hub, switch, or simple router, also in the path.

not quite.  the ethernet interface on the router has no ip address at
all - it talks PPPoE only, which is an unrouted protocol that doesn't
use IP.

You run a PPP daemon on your firewall either with compiled in pppoe
support, or you use a helper program.  This talks PPPoE to the router
and provides a virtual interface on your firewall that takes the ip
address.

Neither of the ethernet interfaces involved are speaking IP, so neither
have an IP address.

Cheers,

Doug.


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