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Random loss of internet

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Note before reading: This is a long post since I've just taken the important parts of information from my post on another forum. I'm not sure if directing to that page is acceptable, so I'm just posting these here.


I've recently started losing internet connection on my desktop pc which runs on Vista Ultimate. It started happening all of a sudden, without any changes to the system / nothing downloaded / installed etc.

What happens it that the internet connection is lost and it cannot be retrieved unless I restart the computer. That's the only way it works so far. When I use ipconfig command at cmd prompt I see that there is no gateway address present when this symptom appears, meaning I can't even reach the modem.

And what's also awkward is that the internet seems to work fine on other pcs connected to the network via WiFi, or iphone etc.

I've tried updating the ethernet card drivers but it didn't help anything.
I've also tried the registry dhcp toggle but it didn't affect the problem at all.

as I said, only restarting the computer fixes it.

PS: A few weeks ago I had a problem with my pc not booting and it was resolved that the problem was with the motherboard. One of the ram slots was causing the problem so I removed the ram from that slot and voila everything was back to normal. I'm just mentioning this because I think it may be relevant.


I've upgraded my modem's firmware during these past 2 days. Done all the windows updates, even updated to Vista SP2. Searched for spyware (got 0 infection results). Still not a single change in my random internet connection losses.
I've also tried other methods to recover the connection. Logging out and back in from windows doesnt work. I've tried disabling the network adapter from Network and Sharing Center -> View Status -> Disable but whenever I click the disable button the window freezes for all eternity. So still, the only solution is restarting the computer.
I'll post 2 ipconfig results, one for when I have internet and one for when I don't.
This is the natural state, with internet connection present: http://www.pastebin.com/m4e464694
This is after loss of internet connection: http://www.pastebin.com/m201fe9d2

I use Zyxel P-660HW-T1 v2 modem.
My ethernet card is Atheros AR8121/AR8113/AR8114 PCI-E Ethernet Controller.
Vista Ultimate SP2.
No software or hardware firewalls present/enabled.


I'd like to point out first that I think I gave a misleading information when I said 'What happens it that the internet connection is lost and it cannot be retrieved unless I restart the computer. That's the only way it works so far. When I use ipconfig command at cmd prompt I see that there is no gateway address present when this symptom appears, meaning I can't even reach the modem.'
I don't know under what circumstances I got the no gateway present result at the CMD screen, but as the CMD logs I've posted and the new ones I've obtained all show, at every point the gateway is handle by so I don't think there is a symptom like no gateway present.

Also I'll post another CMD screen log now, which is again after the loss of internet connection but the ipconfig results are the same as when I do have internet connection, yet the pings don't yield a return.

As for your questions:
1. When the issue happens, can other computers in the network PING this problematic computer?

No they can't, even though they see the network, can ping the gateway and can reach internet, when they ping , I get no return.

2. As you mentioned, restart the computer can fix the issue. I would like to check does the gateway address exist after you restart the computer.

As I've mentioned earlier at this post, that gateway address non-existance isn't present anymore, I can't remember under what circumstances I produced such a result.

3. Is the IP address of this problematic computer configured manually or assigned by the DHCP server?

All the settings are set the Automatically configure IP, DNS etc under IPv4 settings of adapter and such. I've never set a manual configuration. I'm also not really experienced as to what really DHCP server does, but here are a few modifications I've done:
Using these 2 sources, I've tried everything with
DhcpConnDisableBcastFlagToggle - yes 2 conflicting terms but the microsoft site and the other side conflict, yet I've tried both and no results so far.
and finally DhcpConnForceBroadcastFlag which I have set at 0 currently, yet still no improvements.
So I'm not really sure if DHCP server handles my IP address or not, all I can tell is these things I've done and I can point out that it says DHCP enabled under ipconfig /all.

As for your suggestions, I have an onboard NIC I think since the ethernet slot is directly connected to the motherboard.
and I've tried resetting the TCP/IP stack, which also didn't help.


I've decided that the NIC isn't the problem.

to reach that conclusion I've used a wireless USB adapter.
First I've checked usual things like the ethernet cable etc, replaced it yet didn't solve. So I remembered I had a wireless usb adapter. If the problem was nic, I could totally eliminate that probability by using a wireless connection, since the Usb adapter is like another nic. So I removed the ethernet cable, installed the usb adapter, connected to the modem, and to the internet, yet again at a totally random time my internet connection was lost.

Now here is where it gets interesting.

after I lost my internet connection which I was using with my wireless usb adapter, I did NOT restart. instead I removed the usb adapter, replugged the ethernet cable between the modem and my computer, and voila I was back on internet.

now I'm not really sure what this corresponds to, but it definetely means my onboard NIC isnt the problem.


Another update:

I've tried using 2 different modems than my current one, didn't solve anything.

So far:
ISP isn't the problem because the internet is there, I just can't reach it.
Ethernet cable isn't the problem, tried others.
NIC isn't the problem, tried a wireless adapter that produced the same results.
Modem isn't the problem, tried others, same results.

That eliminates the hardware related to internet and networking in my opinion. But I'm not the one with knowledge, so motherboard could also be a problem afaik. But then again it can also be a problem with my system.
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