Windows 7 PC Disables LAN

First of all, hello!

I have a bit of a weird problem; here's the whole story. For the sake of an easier explanation, let us call the PC's I have mentioned PC-A, PC-B and PC-C. So, I first had PC-A and PC-B installed (this was years ago), and the problem first started appearing right away; whenever I tried to transfer a file between the two PC's, that's size exceeded roughly 1 MB, PC-B shut down all connections (which means it lost LAN connectivity, and could therefore not connect to the internet (as the broadband is connected via LAN to the switch)). At first, I didn't think much of this, as the problem is easily avoidable by transferring files using a USB stick instead (Note that smaller files can still be sent without any problem, and the PC's even perform well in Games, when playing LAN). However, I decided to get a third PC (PC-C) up and running recently, and have correctly (as far as I can tell) installed the PC upstairs on a different switch, connected to the LAN and internet as well. However, now the problem has became a bit of a greater nuisance, as whenever I try to send files from PC-A to PC-C, PC-B locks itself down again (my guess is that this happens because the traffic is still being applied to the PC-A-to-PC-B switch, which then leads me to conclude that the problem is in the switch).

I have so far tried changing switches, changing the jack that PC-B is connected to in the switch, changing various options in the Network Adapter settings of PC-B and disconnecting and reconnecting PC-B to the network(both physically, by plugging the cable out and back in, and via the software, by enabling the LAN connection that PC-B is usually connected to as it disables itself after a while (it gets stuck on Enabling... when I try and do this)), and so far the only way to get PC-B's networking working again, is by rebooting the PC itself.

Please also note, that I am able to ping between all PC's before the file transfer, that the other two PC's do NOT need to reboot in order for their network to still function properly, that only files of a filesize of over ~1 MB cause this malfunction, that sometimes (I have yet to see a pattern of this occurring) PC-B CAN ping the other PC's but has a 50% packet loss average, and takes about 3k ms to get a single response, while the regular ping speed is <1 ms, and that transferring files over wireless networks (from PC-A to a laptop connected to the switch or broadband) does not seem to trigger this problem.

Thank you for taking the time to read this wall-o'-text, and for any help you might provide. If more info is needed, just ask.

tl;dr- One PC gets blocked out of the network whenever a "larger" file is being sent over the network, regardless of from which machine to which.
- Xyron​


Noob Whisperer
Hello and welcome to the forum.
Sounds to me like PC-B has a bad network adapter and is likely generating noise that it and possibly the switch port cannot recover from.
Have you looked into installing another NIC into PC-B and swapping out the cable for a known good one? Can you advise, if PC-B is turned off and possibly even unplugged from the network, do other network nodes seem to work without issue? Can you move files larger that 1meg between PC-A and PC-C?
What type of switch(s) are you using on the network (simple unmanaged or managed) managed switchs are a bit more sensitive as to speed and duplex and if you have for some reason set the speed and duplex manually at the adapter level you may have to set the speed and duplex to match exactly for the particular port you are using on the switch, best left to auto negotiate speed and duplex at both ends.

Thank you for the reply.

I haven't looked into the installation of another NIC into PC-B, but now that you mentioned it, I think I should really consider it. The cable I am using is a known good one, as I have already tested it using a different switch and different PC (it performed without any problems). I also tried simply changing the port of the switch to which PC-B was connected, but it didn't fix anything.

The network suffers no effects, regardless of PC-B's state (whether turned on or off) - meaning that I can transfer any files of any size from PC-A to PC-C without problems, it's just PC-B that locks itself out of the LAN (requiring a reboot to fix, as stated before).

As for the switch I am using a simple, unmanaged switch, so I doubt the problem is in the switch (as PC-A and PC-C can still function perfectly fine even after PC-B has it's little episode).

Lastly, I believe that simply adding a network card into PC-B and using it instead of PC-B's onboard network card could fix the whole thing. I will try and acquire a working network card and see if that works (shouldn't be too long before I get one). Again, thank you very much for your reply, and your help was indeed welcome.

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