Internet access through Linksys router intermittent

I have two PCs (XP Pro) connected to a Linksys BEFSR41 router, which is then connected to a DSL modem (AT&T).    I've loaded all the firmware and have the default setup for the router.   I will get it to work and it continues to work throughout a session.   However, I'll shut the computer off and the next time it won't work.

I've updated the network card driver and the Linksys firmware.   I'm starting to think it's an issue with the Windows Firewall, but don't really know.  There have been some recommendations to turn off the Windows firewall - is this a good idea?

I've been able to get it to work by removing the Ethernet cable from the router and connecting directly to the modem.  After loading a webpage, I'll swap the Ethernet cable back to the router and it works just fine.  Go figure??

Does this make any sense?    Also, how should I set up the Linksys for best protection?

Any help is appreciated.  I'm a newbie with networks and a little over my head here.
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deltronicConnect With a Mentor Commented:
The most likely problem is you haven’t configured your router properly, and your Windows XP PC is actually sharing the internet connection instead of your router.

The fist thing is to check your connections.
1-4 is for your computers
Wan Port is for the DSL modem
You will start one of the computers and you should receive an IP address from the router.
I believe the default router address for linksys is Check your network connection, the default gateway is usually your routers IP address.
Once you entered the IP address of your router thru your web browser you can configure your router with the necessary settings, usually PPPOE for DSL.
Check your routers manual if you’re not familiar with the routers config page access. If you don’t have one check the Linksys website.
Your Mac and pc should work fine in no particular startup order.
You might need to remove the internet sharing on the windows XP PC. In the networking connection window.
Also make sure your XP PC has the option in internet explore to (Never establish a connection).

Give that a try.
Does your DSL connection need username/password to connect?
jlaidlawAuthor Commented:
I don't think so.

The fact that it works fine when connected directly to the modem verifies that,  doesn't it?
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Maybe it means the oposite. Don't you have the PC configured to auto connect when the connection drops?

I don't know how dsl works in your country, but here in portugal, you must enter user/pass, either the pc memorizes it,a program specific to the isp memorizes and makes the connection  or a router with internal adsl modem, that has room for the person to save user/pass and it makes the connection itself.

Try going to options in the IE then in connections, see if it has anything there.
is dhcp ON on the linksys router?
jlaidlawAuthor Commented:
I've traced the problem to the iMac (OS 9.1).   I know I said two PCs, that's because I wanted to keep the question simple.   The truth is, I have a PC (XP Pro) and an iMac (OS 9.1) connected to the router.

If I power up the modem and router, then start with the PC, it'll work.

If the modem and router are powered up and initialized with the iMac (PC is off), everything locks up - I can't get get Internet - nothing.  Even if I turn on the PC at this time, I can't get Internet.

At this point, I can disconnect the PC Ethernet cable and connect it directly to the modem and it works (Internet).   Then, I can return the Ethernet cable back to the router and connect the router to the modem and everything continues to work fine...even the iMac will work at this point.

It's almost like the iMac puts a lock router.  

Any ideas?

do you have the dsl modem in the WAN port?  sounds like you have an arp conflict
jlaidlawAuthor Commented:
WAN port?   I'm pretty sure the cables are connected correctly.

There is a group of four ports labeled 1-4: only two used for connection to PC and iMac.   The dsl modem is connected to a stand-alone port on the router.

As I mentioned, it does work if the router is initialized from the PC, first - then both computers can access the Internet.

I'm thinking the iMac is trying take over.   Perhaps I need to assign IPs rather than automatic assignments???
What are you using as the PPPoE connection?  are you using your laptop as the dialer? or are you using the dsl modem or the router??? basically what did you type your username and password in?

are you statically or dynamically setting your IP's?
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