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frankcheong

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unstable network connection

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frankcheong

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The copy is actually scp and is on local lan only.
BTW, have tried ftp and reached the same result.
If you have not, what I would suggest is that you run a packet capture on the two computers invovled while you run a copy and see what is going on.

What is the LAN speed?

Have you checked cabling between the FreeBSD server and the switch port?
Have you tried moving to another switch port?
I have totally 4 machine with this problem and they all are freeBSD, so I highly suspect that this problem is not a physical problem. BTW, these four server are connecting to two different types of network switch and so I also don't think the problem lies on the switch layer. What I can test is to replace one of the cable but also I don't think the problem would lies on the cable side.

I have tested with 1000 base T as well as 100 base T and the problem still exist. Also tested auto neg with the same result.
I would say that if it were a FreeBSD issue that more than just you would have the problem.  I know have I one FreeBSD server and I have no issues with it.

You should list everything about the servers and see what they may have in common.  Things like:

Level of FreeBSD
Amount of RAM
CPU number and speed
Avg. CPU utlization
Amount of memory in use
Avg. network bandwidth utilization
Physical paths between clients and servers

would be a good start.  When you find things that are in common start isolating on those.

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Finally nothing can be done in order to get rid of the problem and thus I have to switch back to linux which the problem simply grows better. I recommend to delete this question.
Dear Sir,

Have you checked path for PMTU blackholes?
Does it work better with Jumbo Frames disabled?
Sorry, since the project schedule is tight and thus I can not wait until I complete testing with all settings. Coz the problem happens quite intermittently. Eventually I have to switch to linux and almost all problems gone (still have intermittent connection failure but the level of intermittent and the no of occurrence reduced dramatically after simply switching to linux).
You (or cableguy in next office) need to troubleshoot network in general, since you have no time to give feedback we are of no help.
Understood. Would still like to give points but actually the problem didn't solve.
problem not solved but would still like to give pts to whom have contributed.
One thing you could try and do to test is to run a packet capture on your server while the network guy does the ping.

If you see the pings come in and go out, then something else is causing the problem.

If you see a ping come in and nothing go out, then something on your server is having a problem.

If you don't see a ping come in, then I would suggest that the network guy mirrors the port you server is on and verify that the switch actually forwarded the packet to your server.