dsl, router and bandwidth loss

Okay, I've been tring to figure this out for about a week now, so that
means the answer is probably obvious. I'm rather new to linux and
networking. Anyway...

I have a local network at home that contains three boxes, a Mandrake box,
an iMac and my girlfriends winblows XP box. They all connect to a Netgear
MR814 router and onto a DSL modem. Now the problem is when I connect any
one of these machines directly to the modem I get a download speed of
around 1.1m/s but once they all get connected to the router and the router
to the modem, I get cut in half (668k). I've tried two seperate routers,
I used to have a halking router and now the netgear, they both do the same
thing.

I thought that if I set up a linux box as a firewall (ClarkConnect) to
connect to the modem and then to the router this would stop the problem,
but no change.

Could my ISP be seeing my local network and cutting my bandwidth in half
because of that? Is that possible? And is there anyway to fake it so
they stop? I don't think it's a setting in the router itself, I've been
through every menu.

Any suggestions would be great.

Thanks.


Here is a my network...

Mandrake Box---------->|------| ClarkConnect
iMac------------------>|router|------> firewall -------->modem---->net
windows xp------------>|------| box

In article <(E-Mail Removed)>, to-double-d wrote:
>
> Here is a my network...
>
> Mandrake Box---------->|------| ClarkConnect
> iMac------------------>|router|------> firewall -------->modem---->net
> windows xp------------>|------| box
>
Run 'tethereal' or 'tcpdump' on the firewall box and see if when you add the
second machine if it is spewing out lots of 'un-authorised' traffic. It is
possible that you have been hit by one of the recent worm's/viruses.

Regards

Alex