I apologize for the long post, but I wanted to include as many details
as possible. Thanks in advance for any information.


Here's my equipment:

DLINK-DI604 router
"VisionNet" modem provided by ISP
Earthlink ADSL


My setup is typical, my PC connects to the router, and the router
connects to the modem, which connects to the outside world.

I use PPPoe to connect to my ISP, and was able to configure the modem
through a web interface (172.16.0.254) with my username and password,
so that the modem acts like a DHCP server.

The router (192.168.0.1) then connects to the modem as a DHCP client.
My PC (and Playstation 2) connect to the router as DHCP clients also.
This setup worked great for many months.

I run Linux, and have a few different server applications that I need
to access from outside of my home. I use dynamic DNS to map my IP to
a hostname. For example, I can connect to my CVS or Apache servers
while at work. I use the router to open the ports that I need and
forward them to the corresponding ports on my Linux machine.

One day, I upgraded the firmware on my router. After re-configuring
it to the proper settings, I discovered that I could no longer connect
to my machine from outside. When typing in my dynamic dns hostname, I
was instead taken to the modem's configuration page. This had NEVER
happened before. Outside requests always went through the modem
straight to the router, which then decided what to do with them.

I struggled and raged about this for a few hours. Eventually, I
modified my modem to just act like a modem (by clicking the "Disable
NAT, Firewall,..." option), and now I configured my router to use
PPPoe to log into my ISP. This creates a situation similar to before,
although I seem to have some occasional DNS problems, and my
connection seems to be a bit slower.

Upon doing this, I can no longer get to the web interface of my modem.
When I attempt to, I am presented with a page titled "Netopia Router"
which says: "Enter username and password for Realm1 at 172.16.0.254".
I've tried my ISP user/pass, empty user/pass, other miscellaneous
things, but nothing works. I can also get to a prompt by trying to
telnet to the modem. It allows 4 failed login attempts and then
disconnects my prompt. I've reset the modem to the default settings,
but the same thing occurs.

So I wonder, what could have happened? I sometimes suspect that my
ISP secretly logged into my modem and upgraded my firmware. I asked
them about this and they denied it, of course, but who knows?


Questions:

1) It's possible that I screwed up my router settings, but why would
that cause my modem to begin intercepting remote requests?

2) My modem says VisionNet on the outside, but when I disable the
advanced settings its messages say "Netopia". Which brand is it? Why
does it prompt me
for a username and password even after I reset it to default settings?
Has my ISP programmed some nonsense into the hardware itself?

3) Why would my new setup cause my connection to be slower? Or cause
occasional DNS problems? It seems to take significantly longer for
host lookups to occur.