Loosing Ethernet Connectivity

[David Schulz]

Hello all,

every once in a while i have a machine (6.1) that out of the blue,  
sometimes after days, some after 6 months, looses Ethernet  
Connectivity. My Machines just run some Service, and have no  
Keyboard / Mouse or Monitor. When the Machine goes down, eg, i am  
unable to ping it from another Machine on the Network, even  
restarting the machine using "reboot" will not fix the Problem. The  
only way to fix it is to login as root, and issue a "ifconfig vr0  
down && ifconfig vr0 up". Then a dmesg Message appears : "vr0: Using  
force reset command.", and after that i can successfully ping the  
machine again. I have had this Problem on different machines with  
different Network Cards, on different Ethernet Cables, and with  
FreeBSD Versions 5.5 until 6.1.

Can anyone please help me to understand and possibly even fix this  
Problem?

Thanks a lot,
David