Networks A little problem with networking...

Ok, I have just a little problem with my networking, mainly the internet. I have a D-Link router installed to split the broadband connection over two PC's, the one I'm writing this on right now, and the one that sits in my bedroom. Yesterday-morning, when I woke up and had to have that little shot of bit-tech for me to wake up better, I couldn't access the internet. What was more, I couldn't access the PC downstairs which I normally can (through the built-in switch in the router). And, on top of that, the PC downstairs could access the internet.

Today, nothing has changed as of yet. I've tried moving my PC downstairs and connecting it with a local strand of UTP cable, so to test if it wasn't the cable that ran from the router to the bedroom. Still no worky.

I've tried connecting my PC directly to the Cable modem, it still doesn't work. I've tried resetting the router, nothing helps. I've tried putting the cable in the other onboard NIC I have on my motherboard, but it doesn't help.

It's just like the cable is connected, and my PC tries to send packets through, but it doesn't receive any (that's what it says when I check the status of the NIC anyway).

Today, something else changed. Not only can't I go on the internet, but the cable isn't detected either. Not by the router (the appropriate LED doesn't light) nor by my PC (the drivers say the cable isn't connected, for both NIC's).

So, what the hell is going on here?

 

I had some very similar symptoms to you: D-Link router, suddenly couldn't access internet. It actually turned out to be spyware. But I don't think that's the case for you. However, it's always worth checking

And as for connecting directly to the modem, did you change the network settings accordingly?

Reinstall the NIC drivers? I've had lots of trouble with onboard NICs, they never work for me. Although I've not really tried, it's easier just to use a cheap PCI NIC anyway. I would say, try another network card if you can. The cheapest I've found is £3.50+VAT - hardly a great expense

 

Do you have a spare hub? Try hooking the PC's to the hub and see if there's connection, to rule out a defective router.
And indeed i have seen a similar thing as Tomm® said, an instance of spyware was actually blocking ALL internet access. But i don't think spyware can disable the NIC interface ,yet.
You could also try resetting the router to it's factory defaults.

 

I've tried everything. I installed this USB-> Network adapter I used on my previous PC, but I had the same problems. I tried a differint cable, same. I tried connecting with the new adapter straight on the modem, same problem.

Now the NIC's do detect te cable again, but there has arrised a new problem with the router. Namely, that when I power it up (with UTP cables connected or not, it's the same) and after a few seconds the power-light goes out again.

I've scanned my PC with Ad-Aware, and it found nothing. I don't have any other spyware-scan programs installed on my PC and I can't download any because I have no means to transfer the file from this PC to my "non-working" PC, as this one doesn't has a CD-Writer.

It's scaring me how complex this problem is and I really can't think of anything logical but that there is something wrong with my installation of Windows XP. This doesn't explain the way the router has been reacting though...

 

Have you tried pinging 127.0.0.1 from the one that you're having trouble with?
This should tell you whether or not your NIC is working. If you get a successful ping, then try pinging the router or your other box, I'd try first by ip then try hostnames. If you have a spare PCI NIC you might try installing that too. I would also do what someone else said (can't remember who) and reinstall your network drivers.

I add a similar problem awhile back when I installed my companies VPN software, it totally killed my network settings on my main box. I ended up having to do a reinstall of the OS, but I didn't delete/reformat so I had all my data, it was just a total pain.

 

Cable modems are really anal about working with more than one computer. You have to make sure that all of your computers and hubs / switches are on the inside of a central router. The reason for this is that many cable providers will only give out one IP address, which will either go to the earliest active connection or none at all. If there is a router connected directly after the cable modem, then it will create a NAT type setup where all the traffic will pass through the router and get routed out to the computers as necessary. When this happens, the cable modem only sees the router and not the computers behind it, so it gives its only available IP address to the router. (BTW - In this configuration you need to make sure that your router has the DHCP client turned on.)

Another thing to try is doing a full reset on the cable modem itself. Unplug EVERYTHING from the cable modem, wait 15 seconds or so, and plug everything back in. This should be done everytime that connections to the cable modem are changed so your ISPs DHCP server will issue out an IP address to the new MAC address (a.k.a. computer, networking device, router).

 

Alright, after giving up, and playing UT for a couple of hours, I returned to my desktop to see that the internet is back in here! I've connected my PC directly to the modem, and reset the modem like ^^ said. It took a while, but I now finally have internet. So it's probably the router's fault, as I said, he's been acting weird lately...