Problems switching broadband between computers

M

microsquid

Registered User
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We have microwave broadband at home (Nova Networks)- wired once it enters the house. Up until recently we would just take the LAN cable from one computer (desktop) to the others (laptops) and it always worked fine (better on the laptops, actually).
About a month ago all this stopped, and I can't get any signal to the laptops. We've tried rebooting, powercycling the router, reconfiguring IP/TCP protocols so all the computers are exactly the same, but no use. There's just no signal when you plug the LAN cable into the laptops.
Plug it back into the desktop (wait 5 mins) and bam, it's fine.
Rang Nova and they said that the signal was perfect from their end and they speculated it might be virus related. All computers have been completely scanned and check out as clear.
IT guy from work has no clue either.
Anyone here got any clever ideas?
 
There's just no signal when you plug the LAN cable into the laptops.
Click to expand...

Please expand on what you mean by 'no signal'.

Assuming Windows, can you connect the working machine, Run the following command
Code: 
cmd /K ipconfig /all
and post the output here.

Then connect a non-working machine, wait a minute, and do the same.
 
I'm at work at the moment but I'll do that when i get home.
For the 'no signal' computers IPconfig just shows zeroes for all the addresses. If you try ipconfig /renew you get a message saying 'No signal'.
At the back of the computer you can see the flashing light for outgoing packets, nothing for incoming.
That clearer?
 
Ive seen this type of behaviour before where the machine needs to be rebooted as it seems to have cached any previous IP and wont let a new one be found. Either rebooting the machine (which Im sure youve tried) or using the method of disabling and enabling the card seems to work for me whenever Ive got the issue start> connect to> show all connections. right click on "Local Area Connection" and click disable, then do same again and enable. ... might not work for you but something else to try anyway
 
It sounds like the TCP/IP settings are different on your laptop when compared to the PC. Am I right in assuming that the the Network looks as follows with the PC connected?

Microwave link
======
Modem
=====
|
| Ethernet cable
\/
===
PC
===

And as follows with the laptop

Microwave link
======
Modem
=====
|
| Ethernet cable
\/
===
Laptop
===

If this is the case then according to what you describe there can be nothing wrong with the ethernet link. I would guess that on one of the PCs the TCP/IP stack is set up to use DHCP and on the other the setup uses a static IP address. If I were a betting man I'd guess the static IP address is on the PC and the DHCP is set on the laptop. I would also imagine that the microwave modem has no DHCP server it just uses a static IP address. Hence the laptop fails to acquire an IP address. To fix the problem you need to copy the static IP information on the PC into the TCP/IP settings of the laptop. Hope this helps.
 
Thought about this a bit more - has the firmware on the modem been changed by any chance. This would govern the behaviour of the DHCP server and you may be using an unstable implementation. It would explain having an ethernet link up but having no IP address. Just a guess. Also if you want to check out the exact status of the ethernet link you can see it in windows by going into "connect to" -> "Show all connections" then right click on local area network and finally select Status. This will show you if the Ethernet link is up. If it isn't it could be something like the lan interface being disabled.
 
I've seen a situation where the network port on a laptop has failed in a simmilar fashion. The LED would light up but it was unable to do any real communication. It was sending out DHCP requests but was not picking up the responses. Even configuring a fixed IP address didn't allow it to communicate with the gateway. This failed overnight - one day it was working the next it wasn't. The only solution in this case was to use a PCMCIA network adapter (like this one).
 
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