Network connection problem

Posted on 2005-02-27
Medium Priority
Last Modified: 2013-12-07
Hi Experts, my server as a DC run with Windows 2000 SP2 on IBM netfinity 5100 series, serve as DNS, DHCP. occasionally it loss network connection. I cant reach any host within same segment, by ping them. Get respond by ping its loopback and IP address. If I disable & enable the network connection then no problem to ping any host. Any idea what can be the cause of this problem, which TCPIP layer and ways to trouble-shoot and solve this problem. many thanks.
Question by:cleungsg
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LVL 16

Accepted Solution

samccarthy earned 600 total points
ID: 13416873
Sounds like it could be a flakey NIC.  First I would change my switch port to rule that out.  If you are getting responses from the loopback address and IP, that says TCP/IP is working properly.    I would put in another NIC, Disable the first and see how that one works.  It seems to me to be a physical layer issue.

Expert Comment

ID: 13416881
I would try what sam says above and also what is the setting on the NIC, full duplex, auto, etc.?  Have you tried forcing it to 100 full on both the server and switch?
Also, try swapping the cable, that is an easy thing to try.
anything in the event logs?

Author Comment

ID: 13416911
Hi samccarthy, what could be the cause of the flakey NIC ?
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Author Comment

ID: 13416921
Hi thepunish3r, can you explain more usage of the NIC setting, I need some background understanding before turning them, thanks.
LVL 16

Expert Comment

ID: 13416995
A flakey NIC or Switch port could be caused by heat, cold solder joints, cheap components, power surge or a surge over the Ethernet cabling.  To isolate, you will either have to prove, or disprove what could be the cause.  What Punish is talking about is the actual connection settings of the Nic itself.  Some Switches can be picky about the Auto Setting which is the default on most everything now a days.  Cisco switches seem to be particularly tempermental about this.  If you do this, then you must make the same setting changes on each end.  So if you statically set your NIC to 100 and Full duplex, then you must do the same to the particular port on the switch it is attached to.  It's a good check.  Depending on your switch though, you may not be able to set it there.

Expert Comment

ID: 13417040

I suggest that you try what they have suggested, if in any case, the problem still persists, then try updating your NIC driver. Also, I notice that you're in SP2, it is possible that this is the cause. Some machines in your network might have been affected by a worm/virus that are broadcasting packets and is affecfting your DC. I suggest that you update your DC to SP4 and install the latest critical updates.

Hope this helps


Assisted Solution

thepunish3r earned 450 total points
ID: 13417080
It is just that sometimes you will get better performance or if you have issues like you describe that you can force the speed settings for the switches and the server to communicate.

Basically if your NIC is 100mg and the switch is 10/100 and you force the specific Port on the switch that connects to this specific server to both the same speed you can rule out that there is some packet loss between the 2 devices.

Normally auto is OK but I personally have learned from switch techs and this has varied a bit that if you have any trouble just force the server NIC to 100 Full Duplex and the swithc port to the same.
If you don't want to try to force them to this, at least confirm that the switch port and the server NIC is auto detect.

Here is some info.
i have a link from one of the switch manufacturers I am trying to find, will send soon.

Assisted Solution

by:Gary Gordon
Gary Gordon earned 450 total points
ID: 13417219
I concur with the above and would switch out the nic.  You could mess with the speed of the card in the advanced properties but if all the nics in your net are running at 100mbps and your servers nic is at 10mbps or spotty in the Auto setting then you really have to scrap that nic and replace.  The nic on the server should be in pristine condition because it's failure potentially affects network performance all over the network.

Do experiment with a different port on the switch because an individual port can burn up and it's gone for good.  What's worse than a flakey port are ports that are intermittently flaky.  It takes some work to find those often.  It's not a bad idea to keep a log of all the good and bad ports on your switches and routers.  

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