I am running a small network with 20 or so hosts and a machine running Ubuntu Server 12.04LTS as the gateway. Every few days I find that the network is frozen and that no two machines can communicate. The problem seems to be caused by one of two Linux PC's on the network locking up. I have been chasing the problem for a few months and here is a list of symptoms that I observe when the problem occurs:
The activity lights for all connected ports on my switches are continuously flashing rapidly, even when there should be minimal network traffic.
All ping requests between machines on the network give "Destination Host Unreachable" or "No route to host".
One of the two Linux PC's on the network is powered on but unresponsive. Network activity light is flashing rapidly. Upon restarting, the syslog entries end abruptly without any indications of trouble. One is running Ubuntu 12.04, the other Mint 14.
Disconnecting the problematic machine instantly restores normal network activity, but the trouble machine must be hard reset to clear the problem.
Since the problem is tied to two machines with different hardware, but both have an Ubuntu based Linux distro I suspect a software problems. I have searched hard for a solution to this problem but am still quite stumped. Any suggestions?