Comcast modem + linksys router + two computers and I get disconnection!!

I have Comcast high speed connection.
Comcast modem is connected to a LinkSys Router [it is not wireless] and two computers, one XP and one Linux is connected to Router.

Then I keep the Linux connected, the modem lights shows connected and recieving data. but as soon as I start the XP computer, and open the browser, the modems lights go of and I loose the connection!

Or I guess it happens when I do SSH from XP to Linux.

Any clue where the problem might be?
Whenever I diconnect one computer from router, the other one works perfectly. but both at same time cause the Comcast modem to drop the connection!!

Thanks for your help,
Who is Participating?
MarakushConnect With a Mentor Commented:
Some cable providers do not like it when you have a router installed...

So most new routers, have a feature to clone the MAC address of your network card, so it looks like you are not behind a router, but you are a single computer conectting directly to the modem from your home computer...

Are the IP's setup as static or DHCP? What are the IP's of each machine?
If the XP machine is on and the Linux disconnected does it work?

-= Felix =-
Make sure the following are true:

1. Cable modem is plugged into WAN port on router
2. Computers are plugged into LAN ports (1-4 usually) on router
3. WAN link light on router should be lit even without computers connected
4. LAN link lights on router should light up for both computers (on at the same time) even without router connected
5. Like Felix said, the IP address for each machine must be unique, and probably should be handed out by the router (DHCP)

- Jer
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Hmmm might I just add my 2cents ....

Also go into your linksys configuration and clone the MAC address of one of your computers so the Linksys uses the MAC address from one of your network cards.

Nav444Author Commented:
IP of xp is
IP of Linux is

I am not at home now, but i will check the DHCP as soon as I got home and will post more about your questions.

what you mean by "clone the MAC address of one of your computers"?
please give little more explanation.

The Clone MAC feature is generally used because many ISP lock DHCP IP's to the mac address.  So there is a strong chance that most users will not release the IP before making changes with their new router.
Otherwise they have no way of telling if your router is a computer or not. Even though the first six  characters indicate manufacturer they have no way of knowing if it's a linksys router or linksys network card.

-= Felix =-
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