[ltp] A22p - ethernet weirdness (connection dies every 5 min; fixed by unplug/replug)

[Richard Neill]

Dear All,

I wonder whether anyone can advise me what is causing my thinkpad to 
lose its ethernet connection regularly?

Symptom: Every so often (maybe every 5 mins, sometimes more frequently, 
sometimes not for half an hour), the ethernet (inbuilt, eth0) connection 
dies.

Diagnostics:
I have a ping process running constantly, pinging a machine on the local 
network. Sometimes the packets just don't return; sometimes I get 
"destination host unreachable"

Even in the "broken" state, ifplugstatus still reports "link beat 
detected". Likewise, the green (LINK) LED next to the network port 
remains on, and the amber (ACT) LED keeps flashing. ifconfig doesn't 
report any errors. tcpdump goes completely silent.

Unplugging and then re-plugging the network cable (after about 1 second) 
fixes the problem, albeit temporarily.

I assumed that it might be a dodgy network cable, or a dodgy socket on 
the back of the thinkpad. However, I've tried different cables, and when 
I unplug the cable, I am unplugging it from the wall end. (I also tried 
different wall-sockets).

I've also seen this problem when I take the thinkpad to hotels, 
(although I'm not sure I have ever observed it when the thinkpad is 
directly plugged into another pc via a crossover cable).

I'm using Mandrake 10.2 - in the default configuration. Previously, I 
had 9.1, and for the last 6 months, I have had this problem.

Could it be a hardware issue? If not, could it be something weird in the 
OS? Or could it be the switch that the thinkpad is connected to? [If the 
latter, is this a common enough problem that it might have occurred in 
other networks?]


Thanks for your suggestions

Richard



P.S. I just power-cycled the network switch, and the thinkpad has stayed 
connected for the last 10 minutes...which may - or may not - be a 
coincidence. If it is the solution, why are the other machines connected 
to the same switch not experiencing the same problem?