A remote office has a Cisco ASA 5505 connecting the LAN to our HQ LAN via VPN.
When a particular Windows XP PC is connected to the ASA via a switch, the VPN tunnel drops, and after a short while, all connections through the ASA stop working. Disconnect the PC and it all starts working again.
The only time I have seen anything like this happen was when someone created a network loop by connecting two network ports on a switch together, where spanning-tree was disabled. However, we have traced all the cables in this small remote office, and it does appear to be a single PC/NIC causing the problem.
Is there any configuration that could be put on the PC that might result in this sort of behaviour? If so, I can clean it up. If not I can clearly assume that the NIC is faulty, and replace it.
BTW - I am assuming this is a simple layer 2/3 network related issue affecting the router or switch functionality of the ASA. It could of course be something else. Cables and basic network configuration (IP address, Link Speed/Duplex) all checked. ClamWinPortable scan from a USB drive found nothing. No sign of unauthorised software.
Any other suggestions would be welcome.
I would just get a new NIC if this PC wasn't in rural Sierra Leone... If only someone could invent a farcaster or teleportation device.